Unit - 1SCIENCE IN EVERYDAY LIFERole of Science in Everyday Life

1.1 Man – ScienceKey points :

Science changed early man into a civilized man. Early man observed and understood nature and surroundings. He learnt to

produce fire. Early man observed germinating seeds and developed agriculture. He invented

tools to make his work easy. Scientists observe everything critically and make verifications. Artificial fibres (threads) are synthesized using chemicals. Science helped in the construction of huge buildings. Development of science provided protection from dreadful diseases. The needs of growing population are met with the development of Industry. Increased food production was achieved through Green Revolution. Science solves the problems of mankind. But its misuse results in the destruction

of mankind.

III Additional Activities :1. Discuss the relationship between human life and science.2. Refer various magazines and collect information from various magazines about

how science helped in the human development and display in your classroom. 3. Do (Take up) a project in your locality about an issue/ incident in which science

is used for development

EvaluationUnit - I

Role of Science in Everyday Life

I Answer the following questions :1.What is science?Ans: Science is a quest for truth. Science is a systematized body of knowledge and a way of life.2.How has science helped in higher food production ?Ans: Higher food production became inevitable to meet the needs of growing population. Through research new, better varieties of rice, wheat, jowar etc., which are disease resistant and give high yield were produced. This led to Green Revolution3.How did early man learn to cultivate crops ?Ans: Early man while wandering observed seedlings, flowers, fruits and seeds. All these were part of his food. After observing the germinating seeds, he learnt to sow seeds and raise crops. He invented tools to make his work easy.4.What are the various industries established to meet the needs of growing population ?Ans: Various industries were established to meet the needs of growing population. Some of them are - Fertilizer factories, Power Generating Centres, Oil Refining factories, Iron and Steel factories, Pharmaceuticals, Coal industries, Automobile manufacturing industries etc.

5. What are the harmful consequences of human actions ?Ans: The use of nuclear weapon produces radioactive dust which is harmful to human beings, plants and animals. Man is responsible for the environmental pollution caused due to use of pesticides, artificial fertilizers, smoke emitted from vehicles and industrialization. As a result, man is causing harm to other living forms.II Fill in the blanks :

1. The branch of science which deals with the production of artificial fibres is Polimer chemistry

2. To eradicate superstitions scientific knowledge is essential. Unit - 2

LIVING WORLD2.1 Living Organisms – Characteristics

Important points : Growth, locomotion, nutrition, respiration, reproduction etc. are the

characteristics of living organisms. The permanent change in the size of an organism is known as Growth. Growth in animals stop after sometime. But growth in plants is throughout

their life. Animals move. Plants are fixed. Plants prepare their own food materials in the chloroplasts with the help of water,

corbondioxide and sun light. Respiration helps to release the energy present in the food. The process of excreting the waste materials formed in an organism during

metabolism is called Excretion. Responding to various stimuli is a characteristic of living organisms. Living organisms give rise to their off springs to perpetuate their race.

EvaluationI Answer the following questions in 1-2 sentences:

1. What are living organisms? Give two examples.Ans: The things which have life are called living things or living organisms. Ex. Cows,

buffaloes, cats, rats.2. What is meant by growth?

Ans: Permanent change in the size of living organisms is known as Growth. 3. Which process helps organisms to continue their race?

Ans: Reproduction is the process which helps organisms to continue their race.4.Give two examples to show that plants respond to external stimuli.

Ans: When a “touch-me-not” plant is touched, it immediately folds (and droops) its leaves. After some time, the leaves get back to their original state. The shoots of plants grow towards light above the ground. Roots grow deep into the soil. Lotus blooming during day, water lily blooming in the night, sun- flower facing sun, etc. are the responses that plants show to external stimuli.II Answer the following questions in 5-6 sentences :

1. Describe the characteristics of living organisms. Ans: Growth, locomotion, nutrition, respiration, reproduction etc. are the characteristics

of living organisms.

1. Growth: The permanent change in the size of an organism is known as Growth. Growth in animals stops after sometime. But growth in plants is throughout their life.

2. Locomotion: Animals move from one place to another for food, to protect themselves from the attack of other animals and for shelter. Animals possess different organs for locomotion. These are called locomotory organs.

Plants do not move. They remain where they are throughout their life. They are fixed firmly into the soil.

3. Nutrition: Energy is needed for growth, movement and responses of the living organisms. Organisms get energy from the food they take. The energy giving food materials are called nutrients. The complete food which provides all nutrients is called nutritious food.

4. Respiration :Energy is released only when this digested food reacts with oxygen. For this, living organisms take in oxygen from atmosphere through various respiratory organs.

5. Reproduction : All organisms grow, become adults, live for some time (certain period) and then die. But still the living forms do not become extinct. This is because they reproduce to give rise to their off springs.

2. Compare the characteristics of plants and animals.

III Fill in the blanks with suitable words : 1. The permanent change in the size of organism is called growth .2. Gills are the respiratory organs in fish . 3. Lungs are the respiratory organs in animals ( Man).4. Living forms can exist continuously through reproduction .

IV Choose the correct answer : 1. One of the following is not a characteristic of plants ( b ) (a) Growth (b) Locomotion (c) Reproduction (d) Responding to external stimuli.2. The organisms which are capable of using the waste material formed as a result of

metabolism are ( a ) (a) Plants (b) Animals (c) Humans (d) Parasites

Character Plants Animalsfood They prepare their food on

their ownThese will depend on other organisms

locomotion They can not move They have different locomotory organs to move

Inner metabolism

They don’t have blood. They have chloroplast.

Most of the animals have blood circulation system.

respiration They take carbon dioxide They take Oxygengrowth Grow through out their life Growth will stop after some

time.reproduction They produce their

offspring by means of seeds or through their body parts. They produce many a number of young plants during their life time.

They produce offsprings either by laying eggs or giving birth to young ones. Generally they give birth to a small number of young one in their life time.

dependency Newly born plant will not depend on its mother plant or tree.

Generally mother animal help the young ones for some days.

Let us think :1. Imagine the locomotory organs in various animals.2. Why birds can fly in sky, why not humans ?

2.2 Classification of living organisms-Plants and Animals

Important points : The systematic arrangement of living organisms on the basis of their similarities

and differences is called Classification. On the basis of flowers, plants are classified as non flowering plants

(cryptogams ) and flowering plants (phanerogams). Non flowering plants (cryptogams ) are divided into Thallophyta, Bryophyta and

Pteridophyta. In gymnosperms, seeds are not enclosed in the fruit. They are exposed or naked

(visible externally) In angiosperms, the seeds are either monocotyledonous or dicotyledonous. Based on their size, plants are classified as Herbs, Shrubs and Trees. Based on their life span, plants are classified as Annuals, Biennials, Perennials. Based on the presence of notochord, animals are classified as Invertebrates (Non

chordates) and Vertebrates (Chordates)Non chordates are divided into 9 phyla; Chordates are divided into 5 phyla.

Largest number of animals belong to the Phylum Arthropoda. Evaluation

I Answer the following questions in 1,2 sentences :1. What is meant by classification ?

Ans:The systematic arrangement of living organisms on the basis of their similarities and differences is called Classification.

2. Based on flowers, into how many types plants are classified? What are they ? Ans: On the basis of flowers, plants are classified as non flowering plants

(cryptogams ) and flowering plants(phanerogams).Non flowering plants (cryptogams ) are divided into Thallophyta, Bryophyta and Pteridophyta.

The plants that flower and bear fruits are called Flowering Plants or Phanerogams. They can be divided into two groups. They are 1. Gymnosperms and 2. AngiospermsIn gymnosperms, seeds are not enclosed in the fruit. They are exposed or naked (visible externally)In angiosperms, the seeds are either monocotyledonous or dicotyledonous.

3. Into how many classes non flowering plants are divided? What are they ? Ans: Non flowering plants (cryptogams ) are divided into three types. They are

Thallophyta, Bryophyta and Pteridophyta.4. What are herbs ? Give two examples.

Ans: Herbs are small plants with tender stem. They grow upto a height of 3-4 meters. They are upright, without any branches or with fewer branches.Eg. : Paddy, wheat, mustard, brinjal, lady’s finger.

5. Which part of the animal is the basis for main classification of animals ?

Ans: Based on the presence of notochord, animals are classified as Chordates and Non-Chordates. In Chordates, there is a rod like cartilaginous structure known as notochord.

6. What are annuals ? Give two examples.Ans: 1. Annual plants :- The plants which germinate, flower, give fruits and seeds and

complete their life cycle within a year are called annual plants. E.g : Paddy, wheat , beans, pumpkin, lady’s finger.

7. Write about Phylum Coelenterata. Give examples.Ans: Coelenterata – These are diploblastic animals finger like structure called tentacles

are present around the mouth. Ex: Hydra.

8. What do you call the vertebrates which can live on land and in water? Give examples.

Ans: Amphibia They can live both in water and on land. The skin is moist without any scales. They have two pairs of limbs. The heart is three chambered. They are cold blooded animals. Eg. : Frog, Salamander.

II Answer the following in 5,6 sentences :1. Explain the importance of classification.

Ans: For studying various living organisms, they are arranged in a systematic manner. Categorizing the living organisms based on their similarities and differences and arranging them in a systematic manner is known as Classification. The study of classification is known as Taxonomy. Taxonomy is useful to study the living things easily, in a simple manner; to identify a living organism easily; to know the relationships and differences between different organisms; to understand the evolution of living organisms.

Aristotle (384-322 B.C) was the first scientist who made an attempt to classify organisms in a scientific manner.

2. Based on the size of plants, into how many types they are classified ? What are they ? Explain them.

Ans: Plants are also classified based on their size. They are 1.Herbs 2. Shrubs 3. Trees. 1. Herbs :- These are small plants with tender stem. They grow upto a height of

3-4 meters. They are upright, without any branches or with fewer branches.Eg. : Paddy, wheat, mustard, brinjal, lady’s finger.2. Shrubs :- These are average sized plants with hard stem. They have branches which grow from base of the plant. Eg. :Rose, jasmine, lemon, pomegranate, hibiscus.3. Trees :- These are tall plants. They have hard, strong stem. Branches arise at the top (upper part) of the plant. Eg. Mango, neem, tamarind

3. Write about invertebrates.Ans: Invertebrates : Notochord is absent in animals like insects, earthworms and

snails. Such animals are known as invertebrates. They are divided into 9 phyla on the basis of their structure. 1.Protozoa 2.Porifera 3.Coelenterata 4.Platyhelminthes 5.Nemathelminthes 6.Annelida 7.Arthropoda

8.Mollusca 9.Echinodermata 4. Write about the animals having vertebral column.

Ans: Higher Chordates : The animals with vertebral column are divided into five groups. They are 1.Pisces 2. Amphibia 3. Reptilia 4. Aves 5. Mammalia.

III Fill in the banks :1. The study of classification is called taxonomy2. Mould on bread is an example for fungi3. Plants which complete their life span within one year are called annual plant4. In vertebrates, rod like structure made of cartilage is called notochord5. In higher vertebrates, notochord is converted into vertebral column6. Animals which can change their body temperature in accordance with the

surroundings are called PiscesIV Multiple choice questions :

1. Algae belong to this class ( a )(a) Thallophyta (b)Bryophyta (c) Pteridophyta (d) None of these

2. Smooth carpet like plants growing on moist wall belong to this class ( b )(a) Thallophyta (b) Bryophyta (c) Pteridophyta (d) None of these

3. One of the following is an example for dicotyledonous plant ( d )(a) Coconut (b) Paddy (c) Jowar (d) Mango

4. An example for annuals ( a )(a) Paddy (b) Carrot (c) Neem (d) Coconut

5. Largest number of animals belong to this Phylum ( c )(a) Protozoa (b) Coelenterata (c) Arthropoda (d) Mollusca.

6. Animal with three chambered heart is ( d )(a) Pigeon (b) Cow (c) Fish (d) Lizard.

7. Plants are given more importance in this medicine ( a )(a) Ayurvedic. (b) Allopathy (c) Unani (d) Homeopathy

2.3 Parts of a plant- their functions Important Points :

The flowering plant has root system and shoot system. Roots absorb water and minerals from the soil and supply them to leaves through

stem. Stem establishes relationship between roots, branches and leaves. Leaf base, petiole, lamina etc. are the parts of a leaf. Leaves prepare food material by the process called photosynthesis. There are four parts (whorls) in a flower- calyx, corolla, androecium and

gynoecium. Flower consists of reproductive parts. Androecium and gynoecium are the reproductive parts of a flower.

EvaluationI Answer the following questions in 1,2 sentences :

1. What are fibrous roots ?Ans: In plants like paddy, grass we find many small roots arising from the point where

the stem touches the ground. These roots are called fibrous roots.2. What is a stem ?

Ans: The part of the plant which grows vertically above the ground is called Stem.3. How many important parts are there in a leaf? What are they ?

Ans: Parts of a leaf : There are three important parts in a leaf. They are- 1. Leaf base

2.Petiole 3.Lamina or leaf blade.4. Name the parts of gynoecium.

Ans: It consists of three parts namely ovary, style and stigma. 5. What is the function of petals ?Ans: It attracts insects and helps in pollination.

6. What is the function of petiole ?Ans: Functions of Petiole :– The stem like part of the leaf that joins the leaf blade to

the stem is known as petiole or leaf stalk. It gives support to the leaf. It helps in the transportation of water from stem to leaf and food materials from leaf to stem.

7. What is the function of stem in desert plants ?Ans: In desert plants, the stem performs photosynthesis. Eg. Opuntia ,Cactus.

8.Why are there aerial roots in banyan tree ?Ans: In some trees, when branches are widely spread, some roots arise from the

branches and give support to the main stem. Eg. Aerial roots of Banyan tree.II Answer the following questions in 5-6 sentences :

1. Explain the root system with the help of a diagram.Ans: The part of a plant that lies below the surface of the soil is root.’ It is light in

colour, has many branches. In plants like marigold, main root grows vertically downwards into the soil. This is called ‘Tap Root’ or ‘Parent Root’ In plants like paddy, grass we find many small roots arising from the point where the stem touches the ground. These roots are called fibrous roots.

2. Write the functions of stem.

Ans: 1. Gives support to branches, leaves and fruits. 2. Establishes connection between roots and leaves. 3. Supplies water and minerals dissolved in water from roots to leaves, flowers and fruits. 4. Supplies the food material prepared in the leaves to roots and other parts of the plant. 5. In young plants, the stem also performs photosynthesis. 6. In some plants, the stem stores the food material. Eg. Sugarcane, Turmeric, Ginger, Potato, Garlic. 7.In desert plants, the stem performs photosynthesis. Eg. Opuntia ,Cactus. 8.Gives support to climbers.

3. What are the functions of leaf?Ans: 1. Prepares food material by the process called photosynthesis.2. Regulates the

consumption of oxygen and carbon dioxide.3.Regulates the transportation of water and salts by the process called transpiration. 4. Modifies as thorns in desert plants and helps in withstanding water scarcity. Eg. Opuntia. 5. Modifies as coiled structures/ climbers in weak stemmed plants and helps in climbing. Eg. Pea plant. 6. Helps in vegetative reproduction. Eg. Bryophyllum.

4. Write about the male and female reproductive parts of a flower.Ans: 1. Androecium :– Androecium consists of stamens. Each stamen is made up

of a filament and anther. Anther consists of pollen grains. It is the male reproductive organ.

2. Gynoecium / pistil :– Pistil is the female reproductive organ. It consists of three parts namely ovary, style and stigma. Ovules develop in the ovary. These ovules have egg which is fertilized by pollen grains during fertilization process produce seeds.

5. What are the functions of flower?1. Flower consists of different reproductive organs and help in the survival of respective species. 2.Flowers help in Beautification of nature. 3. Flowerdevelop into fruits. 4. Flowers Develop seeds which are responsible for giving rise to new plants. 5. Flower contains nectar to attract insects.

6. Draw a labeled diagram showing the parts of a flower. stigma anther filament style calyx ovary ovulescorolla

6. Draw a labeled diagram of a leaf.

III Fill in the blanks :

1. The plants without tap root system have fibrous roots.2. The part of the stem where the leaf arises is called nodes.3. The food material prepared in the leaves is transported to roots and other parts of

the plant by stem.4. The lower part of the leaf which is attached to the stem near the node is

called leaf base5. The ridged structures which divide into many branches and spread in the lamina

are called veins.6. The female reproductive organ in the flower is Gynoecium / pistil

IV Multiple choice :1. The roots which support the branches of banyan tree from breaking are –––– .

(a) tap root (b) fibrous root (c) rootlets (d) aerial roots ( d )2. The part of the plant that performs photosynthesis in the young plant is ––– .

(a) root (b) stem (c) flower (d) fruit ( b )3. Vegetative reproduction in bryophyllum takes place by –––––––––––– .

(a) root (b) stem (c) leaf (d) flower ( c ) 4. The part of the flower that attracts insects and help in cross pollination is ––.

(a) calyx (b) corolla (c) androecium (d) gynoecium ( b )5. The number of whorls in which parts of a flower are arranged is

(a) 2 (b) 3 (c) 4 (d) 5 ( c )

2.4 Organ systems in Animals 2.5 Organ systems in Human body

Important Points : Unicellular organisms perform different metabolic activities in their cell. Multicellular organisms have different organ systems to perform different

metabolic activities. Circulatory system transports digested food and oxygen from blood to different

cells in the body. Integumentary system covers all parts of the body and gives protection. Nervous system shows responses to the external stimuli. Reproductive system saves the living species from extinction and helps in the

production of offsprings. In humans, Digestive system consists of mouth, pharynx, oesophagus, stomach,

small intestine, rectum and anus. In humans, Circulatory system consists of heart, blood vessels and blood. In humans, Respiratory system consists of nose, pharynx, trachea, bronchi,

bronchioles, lungs. In humans, the Nervous system is divided into three categories: 1. Central

Nervous System 2. Peripheral Nervous System 3. Autonomous Nervous System.

Kidneys, lungs and skin are excretory organs.

EvaluationI Answer the following questions in 1-2 sentences :

1. There are no organs in amoeba to perform different functions. Why?Ans: Amoeba is a Unicellular organism. Multicellular organisms possess different

organs to perform different metabolic activities. Unicellular organism performs different metabolic activities in its cell itself.

2. Mention various organ systems in animals.Ans: Different organ systems in animals are-

1. Digestive system 2. Respiratory system 3. Circulatory system 4. Excretory system 5. Integumentary system 6. Muscular system 7. Skeletal system 8. Nervous system 9. Endocrine system 10. Reproductive system . 3. Write about integumentary system.Ans: Integumentary system Covers all parts of the body and gives protection.

Regulates body temperature.Excretes wastes present in blood through skin.3. Write about reproductive system.

Ans: Reproductive system-It helps in the production of new organisms and perpetuation of race so that living species do not become extinct.

II Answer the following in 5,6 sentences : 1. Explain digestive system in human beings.

Ans:Digestion is the process of breaking down of complex food materials into simple forms which can release energy.Digestive system consists of a pipe like alimentary canal and digestive glands. Alimentary canal is in different shapes in the form of different organs. The important parts of alimentary canal are mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.

2. What is the relationship between immune system and blood?Ans:Immune means protection from diseases. The system which protects our body

from diseases is called immune system. The white blood cells present in the blood fight against the disease causing organisms. So W.B.C (White Blood Cells) acts as police men and protect our body from diseases.

3. Draw a neat labeled diagram of respiratory system.Ans:4. Write about the system which is responsible for stimulus- response.Ans: When we touch an object, we will know whether it is hot or cold. When a thorn

pricks our foot, we immediately withdraw our foot and take away the thorn. All these actions take place under the control of nervous system.

4. How is the skin useful in excretion ?

Ans: The sweat glands present in the skin collect the toxins present in the blood that is circulated through the blood vessels to the skin membrane. These toxins are excreted in the form of sweat through sweat pores.

III Fill in the blanks with appropriate words : 1. Movement of muscles promote movement of different organs.2. The organ system which secretes hormones is Endocrine system.

3. Salivary glands secrete saliva into mouth.4. In humans heart is present in rib cage between two lungs.5. Trachea is made up of C shaped ring like structures.6. Brain weighs about 1200 - 1400 grams.7. In males testes are the reproductive organs.8. In females, the female gametes are known as ovums

2.6 Microbes

Important Points :

The micro organisms which are minute and are not visible to our naked eye are called micro organisms.

Viruses, bacteria and protozoans are micro organisms.

Micro organisms help in the preparation of bio fertilizers.

Bacteria produce bio gas.

Harmful bacteria cause diseases in plants,animals and humans.

HIV leads to AIDS.

EvaluationI Answer the following questions in 1, 2 sentences :

1. What are micro organisms?

Ans: The organisms which are minute and are not visible to our naked eye are called micro organisms. Viruses, bacteria and protozoans are some micro organisms.

2. Mention the different shapes of micro organisms.Ans: The micro organisms are in different shapes. They may be rod, spherical(round),

comma, spiral shaped. They exist either independently or in groups.

3. In what way rhizobium bacteria are helpful to crops?

Ans: Rhizobium bacteria present in the root nodules of leguminous plants fix the atmospheric nitrogen i.e., they change atmospheric nitrogen to nitrates and make them available to plant. Otherwise plants cannot take atmospheric nitrogen directly. These bacteria are also called nitrogen fixing bacteria.

4. What are disease causing organisms?Ans: The microbes (viruses, bacteria) which cause diseases are called disease causing

micro organisms. They spread from one person to another by direct contact, air, water, food, insects and animals.

5. Expand HIV .Ans: HIV is a micro organism. HIV means:

H – Human I – Immuno deficiency V – Virus

II Answer the following questions in 5, 6 sentences : 1. Write briefly about viruses.Ans: Viruses are very simple in structure. They have genetic material enclosed in a

protein coat. Some viruses are rod shaped while some others have head and tail. They cannot prepare food on their own. They live in plant cells, animal cells, bacterial cells, air and water.

2. Describe bacteria.Ans: In bacteria, genetic material and cytoplasm are enclosed in a thick cell wall. They

have delicate filament like structures called Flagella. The number of flagella varies from one to many. They may be present at one end of the body (cell), at two ends or all over the body.

3. How are micro organisms helpful in the preparation of food?Ans: Some microbes are helpful in the preparation of food. Lactic acid bacteria turns

milk into curd. Curd has good nutritional value. Cheese is prepared by adding microbes to milk. Microbes ferment the dough required to prepare bread, idli,

dosa etc. Some vitamins that are essential for human beings are also prepared by microbes.

4. What are the diseases caused in humans and animals due to bacteria.Ans:

III Fill in the blanks with suitable words : 1. The study of microorganisms is called micro biology.2. The bacteria which change milk into curd are Lactic Acid Bacteria.3. Methanogenic bacteria produce bio gas.4. Blue tongue disease is seen in sheep.5. Polio is also called as Influenza or infant paralysis.6. There is no cure to AIDS. Prevention is the only way.

IV Multiple choice questions :

1. This crop is affected with “ Root Wilt ” ( b )(a) Ground nut (b) Coconut (c) Chilli (d) Sweet Lemon.

2. Rubella is another name of this disease. ( c )(a) Plants (b) Animals (c) Humans (d) Mall

3. 50% of the people infected with AIDS are in the age group of ( a )(a) 15-29 (b) 10-13 (c) 40-50 (d) 60-70

Unit - 3MATERIALS

3.1 Materials of daily use

We use many things in our daily life. We call them objects. We use rocks/stones, wood, iron to build houses. A house protect us from sunlight, cold and rain. Clothes protect our body from heat, cold, dust and disease causing bacteria. Clothes are made up of different materials.

We wear suitable clothes according to the climatic conditions. We wear cotton clothes in summer and woolen clothes (sweaters) in winter to protect us from cold.

How are these clothes made? These are made of different fibres. The fibres are spun into thread and from the threads, clothes are made.

3.1.1 Different types of fibres :Clothes like cotton, silk, wool and jute are made up of natural fibres. Natural

fibres are thick in appearance Clothes like Polyester, Terylene and Acrylic are made up of synthetic/artificial fibres. Synthetic clothes absorb less (quantity of) water. So they dry fast.

Plants Animals Humans Paddy- Blight. Cattle- Mastitis cholera, Typhoid, Citrus- Canker. Sheep- Anthrax, Diptheria, Whooping cough, Chilli- Leaf spot disease. Hemorrhagic septicemia. Tuberculosis, Leprosy,Cabbage- Black rot Entritis Tetanus

Identification of Natural, Artificial Fibres :Activity:- Collect cloth pieces made of natural and artificial fibres. Burn the pieces

of cloth together with the help of tongs as shown in the fig. 3.1Which cloth becomes ash ? Which clothes are shrunk ? Observe and enter in the

table 3.1Table 3.1 Observation of fibres in different clothes

How do you feel Whether it becomes ash when you touch the cloth shrunken when the cloth is burnt

1.2.3.4.5.6.7.

When natural fibres are burnt, they burn and turn into ash. When silk fibres are burnt they give a smell of burning feathers. Wool does not burn quickly. Fibres like Nylon, Polyester, Terylene, Rayon are sythesized from chemicals. When they are burnt they give out odour similar to burning plastics and they shrink.Activity 2 :3.1.2 Observation of thread in different varieties of clothes :

Are all the fibres same in a thread ? Take out the threads from different clothes. Pull the thread and split it into two pieces. Observe the threads. Do you observe fibres clearly for all clothes. Observe threads from each cloth with a magnifying lens. observe the thread whether it is of equal thickness through out its length. Activity 3:3.1.3 Durability of clothes :

Collect threads of equal lengths from different clothes. Hang the threads by fixing one end to a hook, the other end to a plate as shown in the fig 3.2. Increase the weight until the thread break up. Repeat it with all the threads. Observe which thread is strong? Artificial threads are strong. They are more durable.Activity 4 :3.1.4 Clothes - Capacity to absorb Water :

We wash our clothes and dry them. We observe that all the clothes do not get dried up at the same time. Because it depends upon the water absorbed by it. Let us test the capacity of clothes to absorb water.

Take a bangle and fix a piece of cloth around it. Stretch and pick it tightly as shown in the picture 3.3. Take some coloured water with a filler and put drop by drop in the middle of the cloth. Count the drops you put on the cloth until it get wet till the edges of the bangle. Watch the time with the help or a stop clock. Repeat it using different types of clothes and enter in the table 3.2.

Table 3.2 Calculation of time for getting wet and dry of clothesNo. of drops required to wet till the edge of

the bangle1. Cotton2. Polyester3. Silk4. Wool5. Terylene

By the above activity we can understand that cotton and wool absorb more water and also take more time to dry.Differences between Natural and Artificial Fibres : S. No. Natural Fibres Artificial Fibres 1. Natural fibres like cotton, wool, silk 1. Artificial fibres like Rayon, Nylon,

obtain from plants and animals. Polyester are synthesized by using chemicals.

2. These are not even in size. Strands are 2. These are even in size. Strands are not too long. long.

3. Not durable 3. Strong and durable.4. Absorbs more water quickly and 4. Absorbs less water and takes short

takes long time to dry. time to dry.5. Coarse on touching (except silk, 5. Soft and smooth when we touch it.

Silk is soft)6. Turns into ashes on burning. 6. They shrink when burnt and gives

the smell of burnt plastic.7. Heavy in weight. 7. Light in weight.8. Looses colour easily 8. Long lasting colours.9. Wrinkles form when they get wet. 9. No formation of wrinkles when

they get wet.

3.15 Natural fibres :(i) Cotton :

Cotton is the best amongst all other fibres. It is obtained from the cotton balls. The long hair like fibres on each seed are called “lint”.

Cotton is spun into yarn. Cloth made by spinning on handlooms is called “Khadi” or “Khaddar”. Gandhiji used to wear Khaddar clothes. Cotton clothes give comfort to the body in summer.

Production of Cotton Fibre:- Generally cotton bolls are picked by hand, fibres are then separated from the seeds by combing in the mills. This process is called “ginning” of cotton.

Spinning:- Cleaned cotton is drawn out and twisted to from yarn. Simple device used for spinning in the houses as shown in fig 3.4 is a hand spindle, called “Takli” and “Charka”. But this process takes much time and laborious. So spinning of yarn on a large scale is done with the help of spinning in the mills.

Fig 3.4The process of making yarn from cotton fibres is called Spinning.

Weaving :- You might have noticed that a fabric is made up of two sets of yarns arranged together (horizontally and vertically) as shown in the fig.3.5. This process of arranging two sets of yarns together to make fabric is “Weaving”, Weaving of fabric is done on looms.

In cotton mills, separation of seeds, ginning, spinning of yarn and weaving are done by the machines. Some professionals make fabric on handlooms. These are operated by hands and legs/or (limbs) of a person.

Some looms which are operated by the electrical motors are called “Power Looms”. (Fig 3.7)(ii) Silk :

We wear silk clothes on special days like festivals and functions. These clothes are smooth and soft. Dust particles cannot stick to the silk cloth. Silk is obtained from the cocoons of the silk moth. The larva of silkmoth i.e., Caterpillar completely covers itself by silk fibres and turns into pupa. This is known as “Cocoon”.

Silk worms are reared in silk Industries. Worms are kept in bamboo trays along with chopped mulberry leaves. Worms eat mulberry leaves and spin cocoons. Silk thread is obtained from these cocoons.

Georgette, velvet, satin, and silk fabric are prepared from silk thread. And it is also used in making parachutes and ropes of parachutes.(iii) Wool:

We wear woolen clothes in winter to keep our body warm. Wool does not let the body warmth out. So we feel warm. Wool is obtained from the fur of the sheep and some other animals. After cutting the fur from the sheep it is washed and dried. Then it is bleached and dyed. The fibres are spinned into thread. Wool fibre is elastic. (iv) Threads from fibre plants :

We use ropes, strings, bags in our everyday life. We get all these from plant fibre. Some of these fibres include

Jute Fibre:- We store rice, sugar in gunny bags. These bags are made up of jute. Jute is mainly cultivated in India.

The stems of the harvested plants are immersed in water for few days. Stems become rot and fibres are separated. These fibres are spinned as threads and ropes. This process is called “Retting”. Gunny bags, Hand bags are made up of jute.

Coconut Fibre:- Coconut fibre is obtained from outer layer of coconut fruit. Ropes, door mats and decorative items are prepared from the coconut fibres.

Flax:- We get this fibre from the stem of the plant. Flax fibre is used to prepare ropes and papers of good quality.Important Points :

Cotton, Wool, Silk are Natural Fibres Polyester, Terylene are synthesized from chemicals. They are called artificial

fibres. Natural fibres absorb more water than artificial fibres. Artificial fibres dry up

quickly. Artificial fibres are even in size along the length of thread and they are strong. Cotton fibre is used to make cotton fabric. Fabric can be woven on handlooms.

Power looms produce fabric on a large scale. Silk fibre forms at the stage of pupa of silk moth. Wool is obtained from the fur of sheep. Jute is used in manufacturing gunny bags, ropes etc. Fibre from external layer of coconut fruit is used to prepare ropes.

EvaluationI Fill in the blanks :

1. Fibres obtained from plants and animals are called natural fibres.2. Cotton Yarn is obtained from cotton plant.3. Silk moths eat mulberry leaves.

II Choose the correct answer :1. An example for artificial fibres is ( a )

(a) Rayon (b) Yarn (c) Silk (d) Wool2. One of the following is the natural fibre. ( c )

(a) Nylon (b) Rayon (c) Silk (d) Polyster3. The hand woven fabric in the following is ( d )

(a) Rayon (b) Nylon (c) Polyster (d) Khadi4. Long, hair like fibres on cotton seed are called ( d )

(a) Yarn (b) Keratin (c) Khaddar (d) Lint III Answer the following questions :

1. Give two examples to each of following.Ans: (a) Fibres obtained from plants: cotton, wool and silk are natural fibres. (b) Artificial fibres :polyester, rayon, terylene etc., are synthesized from

chemicals. Hence they are called artificial fibres. (c) Fibres obtained from animals: Wool and silk are obtained from animals.

2. Write any five differences between Natural and Artificial fibres ?Ans: Differences between Natural and Artificial Fibres : S. No. Natural Fibres Artificial Fibres 1. Natural fibres like cotton, wool, silk 1.Artificial fibres like Rayon, Nylon,

obtain from plants and animals. Polyester are synthesized by using chemicals.

2. These are not even in size. Strands are 2. These are even in size. Strands are not too long. long.

3. Not durable 3. Strong and durable.4. Absorbs more water quickly and 4. Absorbs less water and takes short

takes long time to dry. time to dry.5. Coarse on touching (except silk, 5. Soft and smooth when we touch it.

Silk is soft)6. Turns into ashes on burning. 6. They shrink when burnt and gives

the smell of burnt plastic.7. Heavy in weight. 7. Light in weight.8. Looses colour easily 8. Long lasting colours.9. Wrinkles form when they get wet. 9. No formation of wrinkles when

they get wet.3. Write about spinning and weaving.

Ans: Spinning:- Cleaned cotton is drawn out and twisted to from yarn. Simple device used for spinning in the houses as shown in fig 3.4 is a hand spindle, called “Takli” and “Charka”. But this process takes much time and laborious. So spinning of yarn on a large scale is done with the help of spinning in the mills.

The process of making yarn from cotton fibres is called Spinning.Weaving :- You might have noticed that a fabric is made up of two sets of yarns arranged together (horizontally and vertically) as shown in the fig.3.5. This process of arranging two sets of yarns together to make fabric is “Weaving”, Weaving of fabric is done on looms.

IV Project :Collect natural and synthetic fabric and exhibit them in the class.

3.2 Different types of matterWe use different things in our daily life.We see matter in different forms like cycle, chair, table, ball, pebbles, stones etc.

in our daily life. All these objects have different shapes, colours and uses.All the above objects are made up of glass, wood, iron and plastic. All these are

made up of matter. Matter occupies space and has weight. Air and water are also used in our day-to-day life. Air and water do not have a particular shape. 3.2.1 Matter is formed by a group of molecules :

Molecules are the smallest particles of a matter which are not visible to the naked eye. Attractive forces are there in between these molecules. These forces are not same in all. Inter molecular attraction is responsible for the change in the states of matter. The attraction force of molecules depends upon their states.3.2.2 Three States of matter :

We see matter in different forms like air, water, glass, wood etc., Matter is divided into three states namely solid, liquid and gases.(i) Solids :

Molecules are very close to one another in solids. Distance between molecules is very less. Force of attraction between molecules is more. So, the solids have definite shape and occupy space and volume. Bricks, Coal, Wood are solids which are hard, Rubber, Thermocoal, Cotton, Wool and Sponge are solids which are soft. Salt and sand are solids which can be poured as heap.

Activity:- Take a broad mouthed bottle. Fill it with glass marbles. Shake the bottle, Fill it with some more marbles and tight the lid. Still you find some gaps between the marbles. Similarly there will be some distance between the molecules of all matters.(ii) Liquids :

Liquids are those which have the capacity to flow. Eg. Water, milk, oil. They occupy space but have no definite shape. If we pour water into a container, it takes the shape of that container.

Molecules in liquids are not closely packed as in solids. Distance between the molecules in liquids is greater than that in solids. Force of attraction between molecules in liquids is less. Therefore they move

freely and can flow.

Liquids occupy more space. Molecules in liquids move in a limited radius. Therefore they have finite volume.

We cannot compress the liquids much. Applying pressure to reduce the volume is called “Compressibility”.

(iii) Gases : Gas cylinders in our houses are filled with compressed gas.Molecules of gas in a balloon are also compressed, because they are loosely

arranged.Force of attraction between the molecules is very less in gases which enables the

molecules to move irregularly. Hence, they do not have definite shape.Examples of gases are smoke, air, oxygen and hydrogen.Activity :- Keep an unlit insense stick in a corner of your room. Smell does not

spread. Now you lit the insence stick, smoke with insence spreads throughout the room. Why ? Fig. 3.9 Molecular Arrangement

Change in the state of matter :Does matter change from one state to another state? How does it change? Activity :- Take some ice blocks in a beaker and heat it on the spirit lamp. Ice

blocks get converted into water. If you heat it continuously, water evaporates. If you catch the vapour and cool it, it becomes water. If you still cool it then it turns back to ice again. Observe the vapour while cooking rice on the stove. And also see the lid of the rice bowl soon after cooking. You may observe the water droplets on it.

Ice block, water, water vapour are solid, liquid and gaseous states of the same matter.

Water is in liquid state when the room temperature is 25C. If the temperature decreases to 0C it changes into ice. If the temperature increases, then it changes into gaseous state.

Ice Water Water VapourThe molecules are of same type in all these states. But their arrangement, internal

force and the attraction of the molecules are the causes for the change in the state. The state of matter depends upon the attraction and distance of the molecules, present in it.

3.2.4 Elements, Mixtures and Compounds :If we spread some sulphur powder on a white paper, we observe small particles on

it with our naked eye. If we pour the sulphur powder in the liquid of carbon-di-sulphide, it then separates into very small particles and dissolve in it. These smallest particles are called “atoms”. We cannot divide these atoms again. Matter is formed by the atoms which are not visible and indivisible. Atoms are the smallest particles in a substance.

Molecules are formed by a group of atoms. Molecules can be formed with the same or different types of atoms. We can see a substance only when it is formed by lakhs of atoms. You can learn in detail about the molecules and atoms in your higher classes.

The black part in the middle of the pencil is made up of graphite. This is another form of Carbon, Graphite consists of only one kind of atoms called Carbon atoms. These are identical (Homogenous).

Water molecules are formed by the different molecules i.e., hydrogen and oxygen. These are non-identical, different (Heterogenous).

Substances are physically divided into three states. They are solids, liquids and gases. In similar way chemically they are divided into three groups. They are elements, compounds, and mixtures Elements are again classified into two they are metals and nonmetals. SubstancesElements :

By combining two hydrogen atoms one hydrogen molecule is formed. In the same way oxygen molecule is formed by two oxygen atoms and chlorine molecule is formed by combining two chlorine atoms. Atoms in an element are of same kind.

Substances formed by the Homogenous atoms are called “elements”. All the substances are made of elements. Nearly 118 elements are discovered so far. Out of these 118 elements 92 are found in Natural state and the remaining elements are made artificially.

Eg:- Carbon, Iron, Sodium are the elements in solid state. Elements in liquid state are Mercury, Bromine. Elements in gaseous state are Nitrogen, Oxygen, Hydrogen.

Metals - Non Metals :Elements are divided into two groups namely Metals, Non - Metals :

Carbon, Oxygen, Chlorine, Bromine, Iodine, Sulphur and Phosphorous are examples of ‘ Nonmetals ’.

Copper, Silver, Gold, Mercury, Calcium, Magnesium, Lead, Iron are examples of ‘ Metals ’.

At room temperature except mercury all the metals are in solid state. Mercury is in liquid state.

We can change metals like Iron, Copper, Tin, Aluminimum into sheets or wires, i.e., metals are malleable. Metals are flexible. Malleability of the metals decreases in this following order :-Gold, Silver, Copper, Tin, Lead, Zinc, Iron, Nickel etc.

Electric current can pass through the metals. Conduction of electricity is not same in all metals. It may be high or low Copper, Silver and Aluminimum are good conductors of electricity.

Heat can pass through the metals. Iron and Copper are good conductors of heat. Non metals are not malleable, do not conduct heat or current except Graphite which is a non-metal.

Compounds :Substances whose molecules consists of two or more different types of atoms are

called “ Compounds ”. For Example water molecule is formed by the combination of Hydrogen and Oxygen atoms

Compounds exist in solid, liquid, gaseous states.Compounds in solid state:- Eg. Sodium Chloride (common salt), Copper

Sulphate (Blue Vitriol), Iron Sulphide etc.Compounds in liquid state:- Eg. Water, Carbon Tetrachloride, Alcohol etc.Compounds in gaseous state:- Carbondioxide, Sulphurdioxide, Hydrogen

Sulphide etc.Hydrogen and Oxygen are gases. Hydrogen is combustible. Oxygen supports

combustion. Water, which is the combination of two i.e., Hydrogen and Oxygen doesn’t burn. The character of the compound formed by the combination of two elements is completely different from elemental components.

Mixtures :The combination of two or more substances without loosing their natural

characteristics are called Mixtures.Combination of elements and compounds form mixtures. The substances present

in the mixture are called constituents. In a mixture the constituents may be present in any proportion. They retain their own properties (characteristics). Elements or compounds in a mixture never combine.

Generally mixtures are of two kinds. (1) Homogenous mixtures:- The constituents in homogenous mixtures are completely soluble. They cannot be identified.

Eg:- Salt water.(2) Heterogenous mixtures:- The constituents in heterogeous mixtures can be

identified. Eg:- Muddy water, stones in rice.

Separation of Mixtures :Husk and stones can be separated by “winnowing”. Waste husk can be removed

from wheat or rice flour by “seiving”.In the rainy season the water contains mud particles. If we keep the water in a

container and allow certain time to settle down, insoluble impurities settle down at the bottom as a residue. The mud can also be separated by mixing ‘alum.’ Mixture of salt and camphor can be separated by evaporation. Tea powder can be separated by filtration from mixture of tea powder and water.

There are so many methods to separate the constituents of the mixtures. Let us know some important methods.

1. Decantation :- When the heavier component in a mixture settles down after water is added to it, the water is removed from the container to the other by the process of “Decantation”.

Activity:- Take a glass of water and pour some sand into the glass, and stir it. Keep the glass in equilibrium position for certain time without disturbing it. Heavy sand settles at the bottom. Now separate the water into another container without disturbing the sand. fig (3.10) Separation of sand from muddy water is also a type of decantation method. Take 25ml. of water and 25ml. of oil in a glass. Stir them well. Leave the glass without disturbing it for some time. Oil and water settles one above the other in the form of layers. Now by separating the liquid into another glass, the two constituents are separated.

2. Filtration:- Decotion of coffee, tea can be separated by the filtration method.Water can be filtered by the water filters or cloth (fig.3.11)Activity:- Take a glass of water and add some mud. Take a filter paper and cut it

in a circular shape. Fold it as shown in the fig 3.12. Take the funnel and make the inner walls of the funnel wet so that when we put the filter paper into it, it sticks to the (wall of inner wall) funnel as shown in the fig 3.12.

Fig 3.12 Making a cone of filter paper (arranging the filter paper into the funnel)- Filtration.

Now pour some muddy water into the filter paper. Then the mud particles settle on the filter paper which is placed in the funnel and the clean water enters into the

beaker through the holes of the funnel. The dirty (mud) particles present on the filter paper are called “residue”. Clean water collected into the beaker is called “filtrate”. You might have seen modern filters in hotels. They can filter the water by special candles.

3. Evaporation :- Add some salt to a glass of water. Pour this salt water into a porcelain bowl and heat it on the water bath. Water evaporates from the salt water leaving behind the salt in the bowl. Observe the fig 3.14

Common salt which is used in our daily life is obtained by evaporation of sea water. This salt water is let into the tanks. By the heat of sun the salt water in the tank evaporates and salt is left as shown in the fig 3.15.3.2.5 Solutions :

Take 50ml of water in two glasses. Add some salt in one glass and some sand in another glass and stir well. Salt will dissolve in the water where as sand will settle down in the second glass. Filter the water of two glasses separately. Sand is separated from water. But salt does not. In the same way some substances dissolve in the water and form “ Homogenous mixtures ”. We cannot Separate them by filtration.

Homogenous mixture of two or more components whose composition may be within certain limits is called “ Solution ”.

Salt dissolves in water and form solution. But sand does not mix with the water so it forms heterogenous mixture. Two or more components are needed to form a solution.Example : - 1. Salt and water.

2. Copper sulphate and water.3. Sugar and water.Salt + Water Salt Solution

Copper sulphate + Water Copper sulphate solutionSugar + Water Sugar solution.In a solution, component which is more in quantity is solvent, which is less in

quantity is solute.Solvent + Solute SolutionWater + Salt Salt solutionIn the above example water is solvent, salt is solute. Activity :- Take two test tubes with 10 ml of water. Add some copper sulphate in

the first tube, powder of naphthalene balls in the second test tube. Observe the first test tube. Copper sulphate dissolves in water. Observe the second test tube. Naphthalene has not dissolved in the water. At the same time take some copper sulphate and mix it with kerosene in one test tube. Take some Naphthalene powder in one test tube and mix it in kerosene. Observe the test tube containing & kerosene copper sulphate is not dissolved in the kerosene. You will observe naphthalene has dissolved in kerosene. And colorless solution appears in the test tube.

Solubility :

Maximum quantity of “ solute ” that dissolves in 100 ml of solvent is called “ solubility ”. Solubility depends upon the attraction forces of solute and solvent items and also depends upon the temperature. If the temperature increases atoms move irregularly and freely. Therefore the solute dissolves more in the solvent.

Example :- Silver Nitrate, Sodium Chloride, Potassium Chloride.

Activity : - Take some water in a vessel. Add some sugar to it, it dissolves. Add some more sugar. Add some more and stir until it remains without dissolving in the water. Then heat it. What do you observe ?

Solubility (increases or decreases) depends upon the rise or fall of temperature.

Important Points :

State of matter depends upon the arrangement of molecules. Matter is found in three states (i) Solid (ii) Liquid (iii) Gaseous. Solids have definite shape. Liquids have no definite shape. Molecules move in a limited area hence they

have definite volume. Gases have no definite shape. Molecules move more freely hence they do not

have definite shape. Matter is made up of atoms. Atoms form a molecule. Element is a substance made up of homogenous atoms. Elements are of two kinds namely Metals and Non-Metals. Compound is a substance made up of heterogenous atoms. Compound is a substance made up of heterogenous atoms. Combination of elements or compounds form mixtures. The components in a mixture retain their properties, hence they can be separated

easily. Components in a mixture can be separated by physical methods. Winnowing, sieving, decantation, filtration, evaporation are the methods to

separate mixtures. Mixture of two or more homogenous components whose composition may be

varied within certain limits is called Solution. Solubility depends upon the attraction forces between solute and solvent and also

on temperature.Evaluation

I Choose the correct word :1. An example of good conductor of heat ( d )

(a) Glass (b) Wood (c) Paper (d) Copper2. One of the following is not a form of water ( d )

(a) Ice (b) Water vapour (c) Liquid (d) Amalgam3. The metal in liquid state is ( c )

(a) Sodium (b) Iron (c) Mercury (d) SilverII Tick the following with True ( ) or False (X)

1. Solids do not flow ()2. Gases have definite volume ( X )3. Liquids have definite volume ()4. By decreasing the temperature physical states of matter can be changed ()5. Air is the mixture of many gases ()

6. Elements have identical atoms ()III Match the following :

1. Salt solution ( c ) (a) Decantation2. Coffee decotion ( d ) (b) Winnowing3. Muddy water ( a ) (c) Evaporation4. Rice and bran ( b ) (d) Filtration

IV Write any 20 substances and divide them into groups as solids, liquids, gases.

V Explain the reasons for the following statements.1. If you open a scent bottle the smell spread throughout the room. Why ?

Ans: When we open the scent bottle, the scent evaporates and changes into gas. The evaporated cent spread in the entire room. So we smell the scent.

2. Hydrogen burns, oxygen helps to burn, but, water helps to control the fire. Why ?Ans: Hydrogen is a combustible gas. So it burns. Oxygen is non combustible gas but

supports the combustion. Water is neither combustible nor supporter. Hence water stops the fire.

3. How will you filter muddy water with a filter paper ?Ans: Take a glass of water and add some mud. Take a filter paper and cut it in a circular

shape. Fold it as shown in the fig 3.12. Take the funnel and make the inner walls of the funnel wet so that when we put the filter paper into it, it sticks to the (wall of inner wall) funnel as shown in the fig.

The above figure shows how to make a cone of filter paper (arranging the filter paper into the funnel)- Filtration. Now pour some muddy water into the filter paper. Then the mud particles settle on the filter paper which is placed in the funnel and the clean water enters into the beaker through the holes of the funnel. The dirty (mud) particles present on the filter paper are called “residue”. Clean water collected into the beaker is called “filtrate”.

4. Lemon juice tastes sour, sweet and salty. Why ?

S.No solids liquids gases1 Bricks Milk Oxygen2 Coal Water Hydrogen3 Wood Oil Air4 Piece of chalk Mercury Helium5 Rubber Petrol Krypton6 Stone Kerosene Carbondioxide7 Marble Diesel Nitrogen8 iron juice argon

Ans: To prepare lemon juice, we add sugar, salt and a spoon of lemon liquid to a glass of water. Lemon is sour in taste; sugar tastes sweet and salt tastes salty. Hence the juice has these three tastes.

VI Write the characteristics of the following : 1 Element: Substances formed by the Homogenous atoms are called “elements”.

All the substances are made of elements. Nearly 118 elements are discovered so far. Out of these 118 elements 92 are found in Natural state and the remaining elements are made artificially.Eg:- Carbon, Iron, Sodium are some of the elements in solid state. Elements in liquid state are Mercury, Bromine etc. Elements in gaseous state are Nitrogen, Oxygen, Hydrogen etc.

2. Mixture: The combination of two or more substances without loosing their natural characteristics are called Mixtures. Combination of elements and compounds form mixtures. The substances present in the mixture are called constituents. In a mixture the constituents may be present in any proportion. They retain their own properties (characteristics). Elements or compounds in a mixture never combine.Generally mixtures are of two kinds.

(1) Homogenous mixtures:- The constituents in homogenous mixtures are completely soluble. They cannot be identified. Eg:- Salt water.(2) Heterogenous mixtures:- The constituents in heterogeous mixtures can be identified. Eg:- Muddy water, stones in rice.

3. Metal: At room temperature except mercury all the metals are in solid state. Mercury is in liquid state.We can change metals like Iron, Copper, Tin, Aluminimum into sheets or wires, i.e., metals are malleable. Metals are flexible. Malleability of the metals decreases in this following order:- Gold, Silver, Copper, Tin, Lead, Zinc, Iron, Nickel etc.Electric current can pass through the metals. Conduction of electricity is not same in all metals. It may be high or low Copper, Silver and Aluminimum are good conductors of electricity.

4. Non - Metal. Carbon, Oxygen, Chlorine, Bromine, Iodine, Sulphur and Phosphorous are examples of ‘ Nonmetals ’.

VII Answer the following :1. How can you say that water is a compound ?

Ans: Substances whose molecules consists of two or more different types of atoms are called “ Compounds ”. For Example water molecule is formed by the combination of Hydrogen and Oxygen atoms

2. How many types of mixtures are there ? Name them.Ans: Generally mixtures are of two kinds. (1) Homogenous mixtures:- The constituents in homogenous mixtures are

completely soluble. They cannot be identified. Eg:- Salt water.(2) Heterogenous mixtures:- The constituents in heterogeous mixtures can be identified. Eg:- Muddy water, stones in rice.

3.How many types of elements are there ? Name them.

Ans: Elements are divided into two groups namely Metals, Non - Metals :Carbon, Oxygen, Chlorine, Bromine, Iodine, Sulphur and Phosphorous are examples of ‘ Nonmetals ’.Copper, Silver, Gold, Mercury, Calcium, Magnesium, Lead, Iron are examples of ‘Metals ’.

VIII Answer the following questions :1. Write two properties of matter ?

Ans: 1. Matter occupies space and has weight. 2. Matter exists in three states. They are solids, liquids and gases.

2. We can store solids, liquids in a container without lid. But we cannot store gas without lid, Why?

Ans: Solids : Molecules are very close to one another in solids. Distance between molecules is very less. Force of attraction between molecules is more. So, the solids have definite shape and occupy space and volume. Hence we can store the solids any where. Liquids : Molecules in liquids are not closely packed as in solids. But the distance between the molecules in liquids is greater than that in solids. Force of attraction between molecules in liquids is less. Therefore they move freely and can flow. Hence we can store gaseous substance in any vessel with or without lid.Gases : Force of attraction between in the gaseous molecules is very less which enables the molecules to move irregularly. Hence, they do not have definite shape. So we can store a gaseous substance only in vessels having a tight lids.

3. Write the differences between solids, liquids and gases.Ans: S.No Property Solids Liquids Gases12345

4. Solids have definite shape and they are strong. Why ?Ans:

5. What constitutes the matter ?Ans:

6. What are compounds.Ans:

7. Give two examples of element.Ans:

8. Gases have no definite shape and volume. Give the reasons.Ans:

9. How do you get salt from sea water ?Ans:

9.What is meant by solubility ?

Ans: IX Fill in the blocks A,B,C,D of the following :

Ice (Solid) Water (liquid) Vapour (gaseous)

1. What is meant by an element?2. Write the differences between mixtures and compounds.3. How can you prove that liquids have no definite shape?4. Write the properties of solids, liquids and gases in the form of table.

X Fill in the blanks with suitable words :1. We get salt from sea by ________________ method.2. We can separate Naphthalene powder and salt by _______________ method.3. Salt is _______________ in salt solution.

Unit - 4MOVING THINGS, PEOPLE AND MOVEMENTS

4.1 MeasurementsIn our daily life we make use of various measurements. We purchase cereals like

rice, wheat, jowar, liquids like milk, oil and kerosene using these measurements. Now let us learn about different systems of measurements. Measurement of length and distance :

Fig. 4.1 Different types of measurementsIn olden days the length of cloth, land and other things were measured using hand

measurements palm, span, cubit, fathom and foot.We can also measure things using these measurements.

Activity 4.1 : Ask four students to measure the length of General Science text book by using

palm and note the values. Let them compare the values and find that the values vary as their palms are of different sizes.This indictes that hand measurements like palm, span, cubit and fathom differ from person to person. But measurement should be the same whoever and wherever it is measured.

A Unit is a standardized quantity of a physical property, used as a factor to express occurring quantities of that property.

The measurement value which is same when measured by anybody at any place is known as standard unit

Scientists have decided to have systems of measurement through out the world to avoid inconvenience and inconsistency.

Measurements used to measure Length, Mass and Time are called Main Measurements. Internationally Standard Units are decided for them. There are mainly three systems of units to measure length, mass and time.

Table - 1

Base UnitsLength Mass Time

1. F. P. S. System Foot Pound Second

2. C.G.S. System Centimeter Gram Second3. M.K.S. System Meter Kilogram Second

M.K.S system is also known as Standard International (S.I) system. C.G. S. and M.K.S Systems are known as metric systems. F.P.S System is known as British system. These Standard Units (S.I) are accepted world wide since 1960. By using these standard units there will be no difference in international discoveries, industries and business.Multiples and Submultiples of Basic Units :

It is not convenient always to use basic units while measuring larger or smaller quantities. In such instances we use multiples or submultiples. For example, it is easy to say the distance between Kurnool and Hyderabad is 200 kilometers than saying 2,00,000 meters. Expressing the length of wall as 30 meters is easier than saying it as 3000 cms. Similarly expressing the yield of a farmer as 120 quintals is easier than saying it as 12,000 kilograms.

1 Kilometer = 1000 meters = 103 meters

1 Metre = 100 Centimeters = 102 cm.1Centimeter = 10 Millimeters 1 Millimeter = 1000 Microns

1 Micron = 1/1000 m.m. = 10-3 m.m.

1 Angstrom = 10-10 Meters = 10-7 m.m.

Here kilometer is multiple of metre and centimeter is sub multiple of metre. Similarly metre and kilometre are multiples of centimeters. Angstrom is used to measure micro measures like length of bacteria, radius of atom etc.

Instruments like scale, tape and survey chains are used to measure distances and length of objects and lands. (Fig 4.2)

Scale shown in the figure 4.3 is used to measure the lengths of objects and geometric figures. What do you observe on the scale ? On the scale you can see centimeters on one side and inches on the otherside.1 centimeter is further divided into 10 millimeters. 1 centimeter = 10 millimeters

Fig. 4.3Least measure we can measure with a scale is millimeter

The smallest quantity that can be measured accurately using any instrument is known as least count of that measuring instrument.Activity 4.2 :

You can find the heights of your class students. Find out who is tallest in your class. Using metre scale and pencil note the measurements from 1 c.m. to 200 c.m. on the wall as shown in the figure 4.4. Each student has to come and stand erect near the wall. Place a cardboard piece on his head and note the measurement of coincidence. Repeat the same with all the students and compare the heights of all students to find who is tallest in the class.Activity 4.3 :

Place the scale to the edge of your notebook (fig 4.5) to the length of your notebook. Scale should not be placed crossly to avoid wrong measurement. Observe

the pictures below. Similarly you can measure the length of pencil, refill, cloth and pillars etc.

Fields, plots and playgrounds are measured by using survey chains or measuring tape as shown in figure 4.6.Activity 4.4 :

Draw a curved line on table or in your notebook and measure the length of it ? How will you measure it ? Take a twine and place it along the curved line from starting to ending. Mark starting and ending points with a ball pen. Then take out the twine and place it straight on the scale. The length of the twine will be the length of curved line.

We cannot measure curved surfaces like edge of glass, circumference of bangle and cylindrical box with scale. These can be measured by twine and the twine can be measured with scale. By using scale we can measure circumference of any curved surface.

Activity 4.5 : Measuring the diameter of wire using scale :- Take the wire whose diameter has

to be measured. Wind it around the pencil as shown in figure 4.8. See that there is no gap between the turns of wire. Measure the length of coil.For example the number of rounds are 24 and the length of coil is 4.8 cms. Then the diametre of wire is 4.8 ÷ 24 = 2 m.m.

Area :- Knowing only length of the room is not sufficient to decide which classroom is bigger. Find out the area of the classrooms to decide which class room is bigger. We find area of regular shapes like triangle, rectangle and square etc. by using formula.

Otherwise area can be found by using graph paper alsoActivity 4.6 :

Big and small squares of 1 cm. and 1 mm. are found in graph paper. Area of big square of 1 cm is 1 cm. × 1 cm. = 1 sq.cm. in 1sq.cm there are small squares of 1 mm long and 1 mm wide, area of these small square is 1 sq. mm. There are 100 small squares in 1 sq.cm.

Fig. 4.10 Graph Paper

The graph paper in fig. 4.10 is of 5 cm length and 3 cm width. It is rectanglular in shape.

Therefore Area = length × breadth.= 5 cm × 3 cm.= 15 Sq. cm.

There are 15 big squares on the graph paper.Area of irregular shapes can be found using graph paper as there is no formula for

finding the area of irregular shapes.Activity 4.7 :

Finding area of a leaf.Place a leaf on the graph paper. Draw the out line of leaf completely. Remove the

leaf and count big squares inside the out line of the leaf. Count the squares which are more than half and leave the squares less than half.

Area of palm, other leaves and any irregular shapes can be found using graph paper.

Volume :The empty space inside the vessel regular, irregular objects is known as volume.

Shapes of vessels in figure 4.12 are different but their volume is same. Area and height of them are different. It means volume depends on base and height of object and can be found using formula.

Volume = length × breadth × heightIn CGS system volume is expressed in Cubic centimetres and in MKS system

cubic metres.1 CC = 1 Milli litre.1000 milli litres = 1 litre.Volume of irregular body cannot be measured by formula. It can be calculated by

using measuring jar or water (unless it is dipped in water).Finding the volume of stone :

Take a measuring jar. Fill half of it with water and note the reading. Hang the stone to the stand with a thread. Arrange the measuring jar as shown in the figure so that stone is dipped in the water. The water level raises in the jar. Note the raised level. The difference between two levels is the volume of stone.

To measure the volume of lime stone which dissolves in water, liquid like kerosene should be used. Lime stone does not dissolve in kerosene.

To measure the volume of liquids measuring jars can be used directly.

Different Measuring Jars :

1. Measuring jar :- This is a cylindrical vessel made of glass or plastic. It is calibrated as shown in fig 4.14. It is used to measure the liquids of desired quantity. Measuring jars of 50 ml. 500 ml and 1000 ml are available for use in laboratories.

2. Measuring Vessels :- As shown in fig. 4.15 they are cylindical in shape with handle. These are made of Aluminium or Plastic. They are used to measure volume of liquids like milk and oil.

3. Pipette :- It is tube like with a cylindrical bulb in the middle. Towards one side of the tube there is a circular mark. Towards the other end of the tube nozzle is present.

From the circular mark to the end of nozzle denotes the volume of pipette. It is used in laboratories to take specific volume of liquid. Liquid is sucked into the pipette through mouth. Precaution should be taken while sucking the liquid so that the liquid does not enter into mouth.

Pipettes are available in 5 ml., 10 ml., 20 ml., 50 ml. sizes.4. Burette :- This appartus is also used in laboratories to extract required volume

of liquid for the experiment. It is made of glass or plastic. It is calibrated from bottom to top. Pinch cock at the bottom is opened to allow the liquid to flow from nozzle. It is convenient to take the desired quantity of liquid for experiment.Important Points :

The measurement value which is same when ever measured by anybody at any place is known as standard unit.

C.G.S. and M.K.S. Systems are known as metric systems.

M.K.S. system is known as S.I. system. S.I. system is accepted as standard system World wide.

Smallest measruements like micron and angstrom are used to measure the lengths of micro organisms like bacteria and radius of atom.

Least count of an instrument is the smallest measurement measured by that instrument.

Area of irregular shaped objects are measured by using a graph paper. Volume of liquids are measured by measuring vessels, measuring jars, pipette,

burette. Pipette and Burette are used in laboratories to find volume of liquids.

EvaluationI Answer the following questions :

1. Where does you use the measurements in your daily life ?2. What is a standard unit ?3. What are the main measurements ?4. Find out the area of your palm ?5. Define volume.6. How do you measure the volume of a liquids by using burette?7. Explain how do you find the volume of a stone.

II Mark right ( ) for the correct and for wrong ( × ) in the brackets against the sentences given:

1. The length of an object is same who ever measures it with their palm. ( )2. Length of curved line is measured by using scale ( )3. 1000 milli litres are equal to one litre. ( )4. Length, breadth and height are necessary to find area ( )

5. Angstrom is used to measure very small measures ( )4.2 Motion

Human beings, animals, worms, insects etc. move from one place to another. Bus, Train, Cycle, Fan, Hands of Clock, Swing, Bell etc. also move in different manner. Planets move around the sun.

Kinds of Motion :

1. Translatory Motion 2. Rotatory Motion 3. Oscillatory Motion 4. Vibratory Motion

1. Translatory Motion :- Motion of a man walking, motion of cycle, bus and car is translatory motion. It is also known as linear motion.

If the position of an object is changing along straight line with respect to a fixed point or object, then the motion of the object is called Translatory Motion.

2. Rotatory Motion :- If the motion of points or parts of an object are along a circular path instead of a straight line, the motion of the body is called Rotatory Motion. Movement of mercry go round, wings of fan and hands of clock belong to this kind of motion. ALl points of that object will be in motion in circular path.

3. Oscillatory Motion :- Oscillatory motion was first observed by scientist Galileo. He observed a hanging lamp in the church. It was moving to and fro from one fixed point and it is repeated for some time. Based on this he made pendulum clock.

Observe the motion of pendulum of a clock.

If you observe these motions, object moves from one place to another on both the sides of a fixed point.

The to and fro motion of an object about a fixed point is called oscillatory motion.

4. Vibratory Motion :- Musical instruments like veena, sitar and guitar have strings in them. If stings are made to vibrate they produce musical sounds

Fig. 4.19 Veena, Sitar From a fixed point or a central point a particle moves to and fro in a straight line

that motion is vibratory motion.When insects like honey bees fly buzzing sound is produced due to vibrations

(caused by moving wings).Force :

Force is necessary to move the objects or to bring motion in the objects.

Fig. 4.20 Fig 4.21

Observe the figures a girl is trying to push the door, a man is trying to lift the suitcase. Force is used in these instances

The pull or push on an object is called ‘ force ’.

Observe the figure 4.22 ox is using force to pull the cart, hence the cart moves. What happens when more load is added ? More force is needed to pull the cart.

The ox has to put more force to pull the cart.Force can push or pull the object. It causes motion in the object.

Fig. 4.22 ox pulling the cart

Issac Newton was the first scientist who identified force scientifically

Movement of an object depends on the direction of the force

Activity :- Ask two students to pull the object on the table from opposite sides and from one side. What is observed?

When equal forces are used on object from different directions resultant force will be different. Force may be increased or decreased.

Speed of cycles, lorries, buses and cars is stopped by using brakes.

Force is that which changes the state of rest or motion of a body.

When more than one force is applied on the object, the resultant force acts on it. Unit of force in CGS system is gram-c.m./second or Dyne, in MKS system Kg-metre / second or Newton.Types of forces :

Scientists have identified some forces in nature. They are gravitational force, centrifugal force and centripetal force.

Gravitational Force :- If any object is released from a height, it falls towards the ground. This was first discovered by the scientist Newton. This is because the earth exerts a force on the falling object. This force is known as gravitational force. This depends on the mass of the object. Gravitational force is there between the moon and earth.

Fig. 4.32Ball released from height reaches ground, any object thrown up it goes up to some

height and comes back to ground.

Centrifugal Force :– A stone tied to the thread can be spinned in circular path. Stone moves in circular path and finger is in centre of the path.

In this motion a force act towards the centre i.e. on finger. The force acting towards centre is called as centrifugal force. Gravitational force acts as centrifugal force when planets move around the Sun.

Centripetal force :– You have understood that centrifugal force acts on a object.Besides this centrifugal force there is another force acting on the object i.e. centripetal force. This force acts outwards to the circular path.Important Points :

Translatory motion, Rotatory motion, Oscillatory motion, vibratory motion are the different kinds of motions.

The pull or push on an object is called force. Direction of the moving object depends on direction of force acting on it. Unit of force in CGS system is gram centimetre/second or Dyne. Unit of force in MKS system is Kg metre/second or Newton. Gravitational force, centrifugal force and centripetal force are the different types

of forces.

EvaluationI Answer the following questions :

1. Explain the different kinds of motion ?2. What is force ?3. Which force acts towards centre when planets move around Sun ?

II Fill in the bllanks :1. The scientist who told about gravitational force for the first time is

——————.2. Unit for force in CGS system is ——————.3. Unit for force in MKS system is ——————.

4. Direction of the moving object depends on —————— acting on it.

Unit - 5HOW THINGS WORK ?

We use many tools, varieties of machines, toys and other things daily. Do you know how they work? Home appliances like fan, T .V, refrigerator, machines in industries work with electricity. Machines like cranes and generators work with mechanical and magnetic energy. Motor vehicles work with chemical energy from fuels like diesel and petrol.

Different energies are used for working of different machines. Energy exists in different forms. In this unit we learn about electricity and magnetic energy.

5.1 MagnetsDid you see magnets ? Did you play with them? Magnets attract some things.You will be astonished if you know that magnetism was discovered by a shepherd.

A shepherd by name Magnus used to take sheep to mount Ida for grazing. One day he observed that his shoes with nails are attracted by a stone. This incident lead to discovery of Magnetism.

Once upon a time people used to say that small ships and boats are attracted by hills. Later it is discovered that some stones in a place called Magnesia in Asia minor region showed this attraction. These stones are called Load stones(natural magnets). The name of Magnet is also derived from the name Magnus. The attractive property of magnets is known as Magnetism.

5.1.1 Things attracted by Magnets :

Activity – 1 :

Place safety pin, alpin, piece of wool, paper, aluminium spoon, porcelein cup, iron nail, plastic comb, etc., on a table. Bring a magnet near to each object and observe what happens.

What do you observe ?

Objects like safety pin, alpin, iron nail are attracted by magnet. This property of the magnets is known as “ attractive property ”.

The objects that are attracted by magnets are called magnetic substances.

Objects like paper, wood are not attracted by magnet objects made of brass and aluminium are also not attracted by magnet.

The objects that are not attracted by magnet are called non-magnetic substances

Magnets are in different shapes. The magnet which is in cuboid shape is called Bar Magnet fig. 5.1 5.1.2 Poles of a Magnet : Activity -2 :

Take some iron filings and a bar magnet as shown in fig.5.2 (a) Roll the bar magnet in the iron filings, observe some iron filings attracted to

magnet. Place the magnet with iron filings on other paper as shown in fig. 5.2 (b) and

observe it.

Fig.5.2 (a) Iron filings and bar magnet Fig.5.2 (b) Bar magnet rolled in iron filings and kept aside

It is observed that lot of iron filings are attracted at the edges and less filings in the middle of the bar magnet. So it is understood that magnetism is more at the edges of magnet.

The edges of magnet where the magnetism is maximum are known as “Magnetic poles “. Every bar magnet has two poles.

5.1.3 Freely hanging suspended bar magnet : Activity – 3 : Tie a thread at the centre point of the bar magnet and hang it freely.

The poles of bar magnet denotes north and south directions of earth. Repeat the experiment 4-5 times in different places in class room. You will observe that magnet always denotes north and south directions of earth only.

Freely suspended hanging bar magnet always denotes north and south directions of earth. This is known as Direction Property of magnet.

Like this we can find directions by using magnets. The pole which denotes north direction is called magnetic north pole (N), the pole which denotes south direction is called magnetic south pole (S). These two poles of Bar magnet are denoted as “N” and “S” letters.On some bar magnets the north pole is denoted by a white dot or a small grove.5.1.4 Compass Needle :

A freely moving magnetic indicator placed on pinpoint and arranged in a circular box is called compass needle (fig.5.4). The circular box is closed with glass.

Fig. 5.3 Compass 1. Tin Box 2. Needle 3. Magnetic indicator 4. Glass cover Indicator in the compass always indicates north and south directions of earth. It is used in ships to find direction. 5.1.5 Attraction and repulsion between magnets :

Did you observe the attraction between magnets any time? Magnets not only attract but also shows repulsion. Let us know about this. Activity – 4 :

Take two bar magnets. Observe their north and south poles Arrange them opposite to each other such that north pole of one magnet faces the south pole of the other magnet as shown in the figure.

(a) North pole of a bar magnet facing south pole of other magnet (b) Slowly bring them closer

(c) Both poles are attracted to each other In this activity keep one bar magnet fixed and move other one slowly. When the second magnet is moving slowly at one point you observe both of them stick together as in fig 5.4 (c)

Now place the north poles of two bar magnets facing each other (a) Slowly push one magnet towards the other. (b)Both the magnets repel each other and move away from each other of like poles.

What is your observation ? Both the magnets repel and move away as shown in fig 5.5 (b)

Same can be observed when both the bar magnets are placed opposite with their south poles. From this it is understood that opposite poles attract ( N-S ) and like poles repel ( N-N, S-S )

Opposite poles of magnet attract and like poles of magnets repel. This is called “ Magnetic pole property ”.

5.1.6 Magnetic Induction : Activity - 5 :

Take a bar magnet, a safety pin and a alpin. Take the magnet near to the safety pin. Safety pin is attracted by the magnet as shown in the fig 5.6. Leave them like that for half an hour.

Then remove the safety pin from magnet. Now take the safety pin near to the alpin, we see the safety pin attracts the pin as shown in the fig 5.6.

Fig 5.6. (a) Safety pin gets the characters of a magnet when it is attracted to the magnet for

some time. (b) Now the safety pin acts like a magnet and attracts the alpin.

Here the magnetism is induced into the safety pin and it acts as a magnet. Magnetism can be induced into substances like iron, steel and nickel. Inducing magnetism into substances is called “ Magnetic Induction ” . 5.1.7 Uses of Magnets :

1. Freely suspended magnet always indicates north and south directions of earth. This direction property is used in making compass which is used in the ships to find directions.

2. Pure stainless steel is not attracted by magnet. The quality of stainless steel can be checked with a magnet while buying.

3. Magnets are used for making speaker of radios, tape recorder and TV.4. Place a magnet in the lid of pin box to handle the pins easily. 5. Magnets are used as door stoppers. One magnet is placed on the door and the

other on wall, the door is attached to wall and doors will not move for the wind. Evaluation

I Answer the following questions :1. What are magnetic poles?

Ans: The edges of magnet where the magnetism is maximum are known as “Magnetic oles “. Every bar magnet has two poles.

2. How do you induce magnetism into an object?Ans: Magnetism can be induced into substances like iron, steel and nickel. Inducing

agnetism into substances is called “ Magnetic Induction ” .

3. Give examples for magnetic and non-magnetic substances.

Ans: The objects that are attracted by magnets are called magnetic substances. Ex. Iron, Nickel, Cobalt.

The objects that are not attracted by magnet are called non-magnetic substances Ex. Wood, Human body

4. Explain the uses of magnets in daily life.

Ans: Machines like cranes and generators work with mechanical and magnetic energy.Magnets are used for making speaker of radios, tape recorder and TV.

5. Draw a neat labelled diagram of compass.Ans:

6. What are the uses of compass?Ans: Indicator in the compass always indicates north and south directions of earth. It is

used in shipsand aeroplanes to find direction. 7. Explain directional property of magnets

II Additional activities :1. Play a role play how Magnus identified the magnet.2. Find the poles for circular magnet and ring magnet.3. Induce magnetism to the magnetic substances like iron, steel etc. Observe which

substance retains the magnetism for long time.4. Take big and small bar magnets. Bring them near with like poles. Observe what

happens—Discuss the reasons.

5.2. Electric Current, Electric Circuits Current has an important role in our life. This current is called electricity.In 600 BC a Greek Scientist Thales used his woollen coat to clean amber. He

observed a strange behavior that amber and woollen coat started attracting pieces of paper and card board.

Later in early 16th century an English Doctor Gilburt proved that the glass rod attracts pieces of paper when it is rubbed with a silk cloth. He named it as Electricity. 5.2.1 Static Electricity :Activity - 1 :

Comb the dry hair many times and bring the comb near to the pieces of paper. Take a glass slab and rub it with woolen cloth and bring it near to the pieces of paper. Observe what happens. Pieces of paper are attracted by comb and glass slab.

This attraction is because of the friction caused due to rubbing each other; the comb and hair, glass slab and woolen cloth.

Electric charge formed due to the friction force remains static at that place only. This is called static electricity.

5.2.2 Electric charges and kinds : All substances have electric charges. Electric charges are of two kinds i.e.

positive charge and negative charge. Normally objects have both the charges equally. So they are neutral. When two objects are rubbed against each other the other charged cells are transferred and opposite electric charges are formed due to friction. Positive charge on one object and negative charge on other object. Positive charge is denoted by + q and negative charge is denoted by – q.

Electric charge is measured in “ Coulombs ”Negatively charged electrons flow through the wires like copper and alluminium.

This flow of electrons is called electric current. The flow of charged electrons in unit time ( one second) is known as Electric Current

“q” coulombs of current passed through a wire in “t” seconds the electric current passed in one second is “ q / t ”. This is called electric current. Electric current i = q / t. Units for current is coulombs / second is also known as an “ Ampere”.

Current is measured in amperes. Ampere =

There are Electric power stations at Nagarjunsagar, Ramagundam and Vijayawada. Power generated in these stations is supplied to different places and electric appliances work with this current.

Electrical cell used in the circuit of radios, tape recorders enables them to work. 5.2.3 Electric Circuit :

Source of electricity or a cell (B), bulb (L), a switch or tap key (K) are connected with electric conducting wire as shown in fig. 5.7 is called electric circuit.

Key or switch in the circuit is denoted by (K) or (.). Source of electricity or battery is denoted by (B). Batteries used in radio and torch light are electric cells. In circuit, battery is a source of electricity and bulb uses current to glow. Switch is used to open and close the circuit.

Now let us find out the flow of electric current in the circuit by closing and opening with switch.

Activity -2 : Take a torch light bulb, battery and switch, connect them by soldering using a

copper wire as shown in the fig.. 5.8. Take the help of your teacher for soldering. This forms the circuit. Now observe the electric current flowing in circuit by operating the switch ON and OFF.

Observe that the bulb glows on flow of current in the circuit when it is closed by putting the switch ON. When the switch is OFF the circuit breaks and the bulb is put off.

Current flows in the circuit when it is closed. Current does not flow when the circuit is open.

Electric appliances like fan, bulb etc., work when switch is ON and the circuit is closed, current flow stops when switch is OFF.

Does Electricity flow in all substances ?

Copper wire is used to form the circuit. Can we use an iron wire or thread instead of copper wire? Let us find out through an activity through which substances electricity doesn’t flow.

Activity – 3 :Take a wooden plank of one square foot, bulb, battery, switch, iron wire,

alluminium wire, thread, a piece of wood and a rubber band. Solder one edge of the copper wire to the switch, bulb and the battery in series on

the wooden plank as shown in the fig. 5.8 Leave the two edges of the wire apart. First join the loose ends of the copper wire with an iron wire and put the switch ON. Observe whether the current flows in the circuit or not.

Similarly repeat with alluminium, thread, wooden piece and rubber band. Observe the flow of current in the circuit when it is connected with different substances and record the details in the table 5.2.

Table 5.2

Substances used to complete the circuit current flows/current doesn’t flowIron wire Alluminium wire Thread Rubber bandCopper wire Wooden piece

What did you observe ? Flow of current occurs only when circuit is completed with metal wires. Flow of

current does not takes place when circuit is completed with thread, rubber band and wooden piece. Metals like copper, Aluminum, iron etc., allow the flow of current.

Substances that allow the flow of current through them are called “ Conductors ”Substances like thread, rubber band and wooden

piece does not allow the flow of current through them Substances that does not allow the flow of current

through them are called “ Non Conductors ’

People and animals get electric shock when they touch live electric wires. So the wires are covered with non conducting materials to avoid the electric shock . The plug and switch we use in our houses are also covered by non conducting materials to avoid electric shock.

You would have noticed the electrician wearing rubber gloves while working with electric appliances.

Rubber chappals can be used to avoid the electric shock when rubber gloves are not available.

Mechanism of torch light : Torch light is used to emit light in the darkness.

Batteries, bulb and switch are the parts of torch light. As shown in the fig. 5.10 there is a hollow cylindrical barrel in torch light. A lid

with screw can be opened and 2 or 3 batteries can be placed in it. Bulb glows when it is switched ON with closed lid. When switch is ON the circuit is completed and the current flows in the circuit and bulb glows. Activity –4 :

Open the torch light and observe how the circuit is formed in the torch light with the help of your Teacher. Important points :

All substances are neutral as they have 2 kinds of electric charges. The two kinds of electric charges are positive charge (+q), negative charge (-q) The electric charge formed due to friction is static at one place hence it is called

static electricity. Electric charge is measured in “ Coulombs” Flow of electrons in unit time is called “electric current “ Electric current is measured in “ Ampere” . Ampere = Source of electricity, electric appliance and switch connected with conductor is

called a “ circuit ”. Current flows in the closed circuit only, current does not flow in a broken circuit. Substances that allow the flow of current through them are called “ Conductors ”. All metals are electric conductors. Substances that does not allow the flow of current through them are called

“ Non Conductors ”. Rubber, wood and plastic are non conductors. Rubber gloves or slippers are used to avoid electric shock while working with

electric appliances. Evaluation

I Answer the following questions : 1. What is an electric current ?2. How many kinds of electric charges are there ? What are they ?3. What are non conductors ? Give examples 4. What precaution should be taken to avoid electric shock ?

II Additional activities : 1. Improvise a low cost torch. 2. Discuss the reason why the crows are not getting electric shock while they stand

on electric lines. Unit - 6

OUR ENVIRONMENTIn the entire solar system Earth is the only planet where life exists. Earth is the

habitat for all the living organisms. Therefore it is known as ‘ Living Planet ’. Animals, plants, physical components like air, water, soil and surroundings

constitute the environment.

Environment is that which includes living and non living components of our surroundings

Broadly speaking environment is divided into two types. 1. Natural Environment 2. Man Made Environment.Natural Environment is divided into two types. 1. Abiotic Environment 2. Biotic Environment.

Fig. 6.1Abiotic Environment

Physical components like light, heat from sun, air, water and soil etc. constitute Abiotic Environment. Soil and land region of earth is known as Lithosphere, Water regions of earth is known as Hydrosphere and gases in the air is known as Atmosphere. 1. Solar Energy :

Sun is the main source of energy on the earth. Sun is 90,960,000 miles away from the earth. All living beings on earth depend on sun for energy. Sun’s radiation on earth is not equal because of elliptical shape of earth. This is the reason for difference in temperatures in different places which led to the formation of deserts, poles and temperate zones.

Solar energy is the main source for growth and development of living organisms. Green plants use solar energy and prepare their food. Solar energy is also essential for some biochemical reactions in animal bodies. It is also essential for regulating the production of growth factors in living organisms.2. Air :

There are many gases like oxygen, carbondioxide, nitrogen, water vapor and others in the air surrounding us. The composition of these gases is balanced in the air. Living organisms help to maintain this balance. They cannot survive without air. They breath in oxygen and breath out carbondioxide during respiration.3. Water :

70% of earth is covered by water. The body of living organisms consists of 70% - 75% of water. Water is used in many ways by animals and plants.

Plants use water for photosynthesis, germination of seeds and in absorption of salts, nutrients and manure.

Animals have lot of water in their body. Water is required for the transport of gases, liquids and digested food, also for excretion of waste material, reproduction and development.

In the atmosphere water is present in the form of water vapor. During day time water absorbs heat from the atmosphere and keeps surroundings cool. Water is also useful for the formation of clouds and rainfall.4. Soil :

Soil covers 30% of the earth. Soil is formed from rocks. Hence it is called lithosphere. Top soft layer of soil is known as ‘ humus ’. Animals that live in air, water and soil depends on soil.

Soil is necessary for the growth of plants. It supplies nutrients, salts to plants. It fixes the plant firmly.

Bacteria which live in soil decompose the dead animals and plants and makes the soil fertile. Soil is essential for livelihood of living organisms.

2. Biotic EnvironmentPlants,animals, micro organisms, fungi etc. are the living components of Biotic

environment. Living components constitute the Biosphere.Plants :

Plants are more in number than animals on this planet. Plants are found in forests, grasslands, water and in our surroundings. Plants provide food to all other living organisms.

Plants produce food for all living organisms on earth by using solar energy. Hence they are called Producers.

Plants prepare their own food. Therefore they are called Autotrophs.

Food products like cereals, fruits, leafy vegetables,vegetables etc. are obtained from plants.

Excess food prepared in the plants are stored in them in the form of starch, oils and proteins.

Plants are called Autotrophs as they prepare their own food.Plants are called Producers as they prepare food.

Fig 6.3 PlantsAnimals :

Animals cannot prepare food on their own. They depend on plants and other animals for food directly or indirectly. Hence they are called heterotrophs. They use the plant products for food. Hence they are called consumers. Based on food habits animals are of three kinds namely herbivores, carnivores and omnivores.

Herbivores :- Animals that feed only on plants are called Herbivores. They consume plants and plant parts. Hence they are called Primary consumers.

Ex. : Cow, goat, rabbit, deer, elephant, grass hopper, etc.Carnivores :– Animals that feed on other animals are called Carnivores.Animals which feed on herbivores are Secondary Consumers. Animals which

feed on carnivores are Tertiary Consumers. Ex. : Tiger, Lion, Cheeta, Wolf, Fox, Jungle cat, Tamed dogs and Cats. Fishes, snakes and some kinds of sea animals.

Omnivores :– Animals which feed on plants and animals are omnivores. Ex. Human beings, bear, crows, sparrows etc.Decomposers :

Organisms which live in soil like bacteria, fungus decompose the dead animals and plants and release different elements. These organisms are known as ‘ Decomposers ’.

The elements released by decomposers are used as nutrients by the plants.Interdependence of plants and animals :

Every living organism need food for energy. They depend on others for food or for some other requirement. Food chains :

The link between the plants and animals for the sake of food is known as Food chain. In a food chain energy is transmitted from one level to another level.

Plants Herbivores CarnivoresProducers Primary consumers Secondary consumers

(First Level) (Second Level) (Tertiary level)

Different food chains are present in the nature.

Plants Goat Tiger(Producer) (Primary Consumer) (Secondary Consumer)

Fig. 6.7 Fig. 6.8

(a) Water Plants (b) Insects (c) Calotes (d) Snake (e) Eagle

Now let us learn the interdependence of plants and animals from the following experiment.Experiment :

Invert a bell jar over a small potted plant. Invert another bell jar over a rat. Place both of them in sunlight. Observe after 4,5 hours. Rat is dead and leaves of plant are withered. What

would be the reason ? This time invert a bell jar over a potted plant and place the rat in the same jar. Observe after 4,5 hours. Plant and rat both are alive. What would be the reason ?

Carbondioxide released by rat is used by plant. Rat breathes the oxygen released by plant.

Insects also can be used in the above experiment.This experiment proves that plants and animals show interdependence for oxygen

and carbondioxide. Animals depend on plants for food directly or indirectly. Excreta of animals are used as manure for the growth of plants.

Some animals live in the hollow of trees, bushes and in the shade of trees. Birds build nests on trees. Many organisms depend on plants. Similarly plants depend on birds, insects, animals and human beings for pollination and dispersal of seeds.

Interaction between Abiotic and Biotic Components Living organisms cannot survive by themselves without depending on non living

or abiotic components. Both of them interact with one another.

Effect of Light on Living organisms :Sun light is very important for the growth of organisms. Plants prepare their food

in the presence of sun light only. This process is known as ‘ Photosynthesis ’. Light is essential for the growth and development of the plants. Plants do not flower when they are kept in darkness.

Plants show different responses to sunlight.Activity :

Take two potted plants.Take two card board boxes and make holes as shown in fig 6.11and place them

over the plants. Water the plants daily. Observe after a week. It is noticed that plants bend towards the sunlight. Human beings and some animals need light for their living.

Effect of temperature on organisms :Plants and animals show certain adaptations to different temperatures. Desert

plants adapt to the high temperatures by certain modifications. They shed the leaves and store water in their stem to reduce the water loss through the leaves.

Ex. :- Cactus, Aloevera, Opuntia.At high temperatures, water is sent out through body in the form of sweat in

human beings and animals. Desert animals have less hair on their body to sustain high temperatures.

Ex. :- Camel lives for 10 days without water. It takes 3-4 buckets of water when water is available. It stores water in its lump and uses water when ever it is required.

Animals in cold places have thick fur or hair. They have thick layer of fat under the skin. This prevents heat loss from the body. Eg. :- Yak.

Siberian cranes migrate to India from Russia during winter and goes back during summer.

Due to effect of temperature there are less organisms in deserts and cold places and more organisms in temperate zones. Plants grow well at temperatures 30-40C.Effect of water on organisms :

Water is a good solvent, therefore many salts dissolve in water. Water is known as universal solvent. Roots of plants absorb the salts dissolved in water. Density of water varies due to changes in temperature. Sometimes water turns acidic due to excess of rain water which resists plant growth. Water is necessary for seeds to germinate. Plants grow well when sufficient water is available.Activity :

Take some seeds in two plates. Pour water into plate ‘A’ till the seeds are submerged. Wet the seeds in plate ‘B’ with little water. Seeds in plate ‘B’ germinate in 4-5 days. Seeds in plate ‘A’ germinate but putrifes. Why ?

This shows that excess water does not help in germination.Activity :

1. Take two potted plants. Water one pot. 2. Leave the second plant without water.3. Note the changes in both the plants and record in your notebook.

Water from water bodies enter air in the form of vapours. Excess water from plants enters air through stomata of plants. This causes changes in the humidity of air.

Water is the important factor for formation of clouds and rainfall.Effect of air on organisms :

Air is a mixture of various gases . This is another important factor needed for plants and animals. Plants and animals on earth take oxygen from air. Aquatic plants and animals take oxygen dissolved in water.

Animals take oxygen released by plants during photosynthesis. Plants use carbondioxide released by animals for photosynthesis.Effect of soil on organisms :

Plants receive nutrients directly or in directly from the soil only. Humus, the top fertile layer of soil is useful for the growth of plants. Soil is the habitat for some living beings.Activity :

Take three disposable glasses. Fill sawdust in first glass, rice bran in second glass and soil in the third glass. Sow seeds in the three glasses and sprinkle some water on them. The seeds germinate in the three glasses but the seeds in the third glass germinate and grow well. What would be the reason.?

The seed in the third glass grow well because there is fertile soil in it.

Soil erosion occurs due to floods, wind currents and human actions like deforestation. Soil erosion can be avoided by growing plants.

SocioCultural Environment Families, human societies, marriage system, religions, culture, law, festivals,

prayer halls, agriculture centres, business centres, training centres, entertainment centres etc. are one part of Socio cultural environment and buildings, bridges, roads, industries etc. which are constructed for the luxurious life of human beings are the other part of Socio cultural environment.

Man has cut down forests for want of land and built sky scrapers and making concrete jungles with advanced science and technology. He established many factories and industries which led to environmental pollution.Important Points :

Biotic and abiotic components in our surroundings are known as environment. Biotic environment and abiotic environment are the two types of natural

environment. Plants, animals and micro organisms constitute biotic environment. Physical components like air, water, soil and solar energy are the components of

abiotic environment. Plants are producers and animals that consume plants are called consumers. The micro organisms that decompose the dead animals and plants are

decomposers. Animals are divided into herbivores, carnivores and omnivores based on food

habits. Biotic and abiotic components depend on one another. Man made environment is also known as socio-cultural environment.

EvaluationI Answer the following questions in 2,3 sentences each :

1. What is environment ?2. What is meant by as biotic environment ?3. Give some examples for socio cultural environment ?4. Define lithosphere.5. What is a foodchain?

II Answer the following questions in 5,6 sentences each :1. Write about any two important biotic components ?2. Explain the relationship between biotic and abiotic components.3. Explain abiotic environment.4. Briefly write about various components of abiotic environment.

III Define the following :1. Hydroshere2. Food Chain.

IV Multiple choice questions :1. The place where the temperature is high ( )

(a) Forest (b) Desert (c) Lakes2. Food chains start with ( )

(a) Bacteria (b) Animals (c) Plants3. Example of man made environment ( )

(a) Bridges (b) Plants (c) Forest4. The factor which helps the preparation of food for plants ( )

(a) Soil (b) Heat (c) LightV Match the following :

1. Hydrosphere ( ) Air around the earth.2. Lithosphere ( ) Our surroundings3. Atmosphere ( ) Water4. Biosphere ( ) Soil5. Environment ( ) Life

VI Give reasons :1. Decrease of quality in environment.2. Interdependance between plants and animals.

VII Pick up the words from the box and make food chains :

1. Plants _____________ _____________

2. ________ _____________ _____________

3. ________ _____________ _____________

VIII Imagine an ideal environment and picturize it with colors :Additional Activity:

See the figure. Potted plant ‘A’ grown in sunlight potted plant ‘B’ grown in darkness. Observe the differences and list them in a table.

Potted Plant - A Potted Plant - B

1. 1.

2. 2.

A BIX Project Work :

Take a card board box and cover the grass in your school garden or in your backyard. Remove the box after few days and observe the grass below it and note the observations.

1. What is the color of grass box ?————————————————————————————

2. Is there any change in grass under the box ? What is the colour of it?————————————————————————————

3. What is the reason for the change in the colour of grass ?————————————————————————————

4. Where do plants grow well ? In darkness or in light ?————————————————————————————

5. Do you recognise the important factor for the growth of plants ? Write down.

————————————————————————————Unit - 7

NATURAL PHENOMENA 7.1 Light

We observe many colorful objects in our surroundings in our daily life. On the way to school we see (many) different types of trees, animals. We can see them during day time. Why ? Can we see them during night time. No. Why ? Can we see objects in a dark room ? No, but when a small candle is lighted in that room, what happens ? All things become visible. We can see them only when there is light. During day time we can see all the things with the help of sunlight. Sun, candle and other light emitters are called Sources of light.

Sources of light : They can be divided into two types.

1. Sources of Natural Light Ex. : Sun, Stars, Glow-worms etc.Sources of Natural light are also called self-luminous bodies.

2. Sources of Artificial Light Ex. : Electric bulb, Torch Light, Candle etc.

7.1.1 Transmission of Light — Types of Substances :When you travel in a bus, you can see outside objects through glass window. It

happens when light on outside objects reaches our eye through the glass window. Can you see outside objects when a metal plate or strip is placed in the place of glass ? No. The type of objects which allow the light to pass through them are called transparent objects.

Substances which allow the light to pass through them - Transparent substances

Can you guess why the things cannot be seen when a metal plate is placed instead of glass ? It is because this metal plate obstructs the light to pass through it to our eyes. Such objects which do not allow light to pass through them are called light resistants or opaque substances.

Substances which do not allow light to pass through them - Opaque substances

Objects cannot be seen clearly when observed through tracing paper or oil paper, because light passes through such objects. They are called semi-transparent or translucent objects.

Substances which allow light to pass through them partially — Semitransparent or translucent substances

7.1.2 Shadow :Activity - 1 :

Take a pen, pencil, rubber, book or any such things and hold infront of sunlight to a certain height. Its shape is formed on the ground like a black spot. This is called its shadow. Sometimes objects can be traced using their shadows.

Shadows are formed when any object is placed in the path of light transmission.

(a) Tree - its shadow (b) Human being - shadow (c) Building - its shadowFig. 7.3

Usually, we can identify real objects with the help of their shadows. But in some situtations we can visualise their illusions. We can make illusions by putting our fingers before light and making interesting figures of animals, birds on walls. There by we cannot say clearly that we can identify real objects by just seeing their shadows in all cases.

Fig. 7.4Shapes of different birds formed with the help of our fingers

Activity - 2 :When colourful flowers like red rose, yellow chrysanthemum, white jasmine and

other coloured objects are placed in the path of sunlight, their shadows are formed. We observe their shadows in black colour only irrespecive of their original colours.

Shadows are black in colour, irrespective of the original colour of the objects

7.1.3 Shadows — Screens which form shadows :Activity 3 :

Switch on torch light on your friend in dark (not laser light). Observe the shadow. Keep one white chart on his behind and again put torch on his face. You can observe some differences between the first and second shadows. The shadow on the chart is more clear. It shows that shadows formed on screens have more clarity.

We see shadows clearly on screen. fig 7.5 shows the shadow on the back of the boy on screen.

Fig. 7.5 Formation of shadows on screen 7.1.4 Can we see Sun and Solar Eclipse directly with our naked eyes ?

We should not see sun directly with naked eye. If we see, the bright rays emitted by sun will damage the sensitive parts of eye and there is a scope for the loss of sight. We should not watch solar eclipse also with our naked eye. Black glasses or x-ray films can be used to observe solar eclipse. Pin hole camera is more suitable for this purpose.

Activity - 4 : Construction of Pin-hole camera is shown in fig 7.6. Take a plastic pipe or tube with 3 inches circumference and 10 inches length. Cover one side of the tube with thick paper by rubber band. Make a hole at the centre of the paper with a pin. Your Pin-hole camera is ready.Precautions to be taken while using Pin-hole camera :

Cover yourself with a black cloth like a photographer. Objects to be seen should be in light. Camera does not work properly in dimlight. Images are formed upside down.

Fig. 7.6 Pin hole Camera7.1.5 Is there any relationship between light and shapes of shadows ?

Activity - 5 :

During a hot morning shadow of a chair is formed in the shape shown in fig 7.7(a).

Now observe the shadow of the chair in the afternoon. Do you see any variation in both the shadows. You can see the changes in their shapes. 7.1.6 Light Emission :

Activity 6 :Take a long plastic pipe (approximately 40 cms.) and observe the tip of the candle

flame through it.Fig. 7.8 (a) Observing the tip of candle flame through a plastic pipe

Now bend the pipe and observe once again as shown in fig 7.8(b). Can you see the tip of the flame ? No.

Fig. 7.8 (b) observing light through bent pipeWhy the flame is visible through plastic pipe and not visible through the through

bent pipe ? The reason for this is, light travels only in straight lines. Hence, tip of the flame can be seen only through straight pipe. Hence, light is not seen through a bent pipe. Light travels in straight line

7.1.7 Reflection of Light — Reflective Surfaces :

Images :

We generally use mirrors to see our images in our houses. When we stand in front of a mirror our image is formed because the light on us reaches mirror and gets reflected from mirror’s surface.

This process of coming back of light rays is termed as reflection and the surface is called Reflective surfaces.

The process of light returning from the surface of a mirror is called reflection. The surfaces which reflect light are called reflective surfaces.

In the same way we can observe images of any object placed infront of a mirror. Sometimes images can be seen even on new steel vessels and ponds where water is still. Hence it is evident that any soft surface like new steel vessel, pond can reflect light like any mirror acting as reflective surfaces.

Smooth surfaces like mirror form Images

Observe the image formed on a mirror fig. 7.9 (a) and the shadow fig. 7.9.(b) and write the differences between shadow and image.

Fig. 7.9 (a) Mirror-Image Fig. 7.9 (b) Light - Shadow

Shadows ImageWe have discussed the formation of shadows and images; Have you noticed the

differences between them at any time ?

Shadows Images1. When light falls on objects their shadows

are formed on their back screen.2. Only the shape of the object is seen clearly

in shadow but not the entire object.

3. Colours cannot be seen. All the shadows are only in black colour.

7.1.8 Additional Activities :

Activity - 7 :Make four students in the class to stand side by side. Ask other student to

hold a big mirror and stand infront of them. Ask the students about the images they see in the mirror.

Activity - 8 :Observe the photograph of a person in a mirror. In a same manner, take a chart

and write a word on it and observe it through a mirror. Can you notice any difference between object and the image.

Fig. 7.10 (b) Observing ImagesThe left and right positions of object become viceversa in images.

Important Points : Sources of light are of two types : Sources of natural light. Ex. : Sun, Stars, Glow-worms. Sources of artificial light. Ex. : Electric bulb, Torch light, Candle. Natural light producers are also called Self luminous bodies. Substances which do not allow light to pass through them are called Opaque

substances. Substances which allow light to pass through them are called Transparent

substances. Substances which allow light to pass through them partally are called

Translucent substances. When Opaque substances are kept in the path of light shadows are formed. Irrespective of colour of the objects, all the shadows are black in colour. Light travels in straight lines. Depending on the direction of the light-transmission the shapes of shadows

change. The process of light returning back from the surface of a mirror is called

Reflection. Smooth surfaces like mirrors create (produce) Images. Mirrors reflect Images.

Evaluation I Answer the following questions :

1. What are self-luminous bodies ? Give examples.Ans: Sun, candle and other light emitters are called Sources of light. Sources of light can be divided into two types. 1.Sources of Natural Light. Ex. : Sun, Stars, Glow-worms etc. 2.Sources of Artificial Light. Ex.: Electric bulb, Torch Light, Candle etc. Sources of Natural light are also called self-luminous bodies.

2. What are opaque substances ? Give examples.Ans: Substances which do not allow light to pass through them are called Opaque

substances. Ex.: wood, human body, paper etc.

3. What are Transparent and Translucent substances ? Ans: Substances which allow light to pass through them are called Transparent

substances. Ex.: glass, water etc.Substances which allow light to pass through them partially are called Translucent substances .Ex.: Grinded glass, greesy paper etc,

4. What are the differences between a shadow and an image

Ans: Shadows Images 1. When light falls on objects their shadows 1. When light from the object falls on

are formed on their back screen. the mirror it gets reflected and thus images are formed.

2. Only the shape of the object is seen clearly in shadow but not the entire object.

3. Colours cannot be seen. All the shadows are only in black colour.

5. How can you prove that light travels in straight lines ? Ans:

6. What is meant by light reflection ? Ans:

7. Can you see your image in a dark room. Give reasons. Ans:

7.2 HeatImportant points :

The coldness or hotness of any place or an object can be known by heat. The capacity to do work is called energy. Heat is the cause and temperature is its effect. Sun is the ultimate source of energy.

Evaluation

Answer the following questions :1. What is heat ?

Ans: The coldness or hotness of any place or an object can be known by heat.2. How can you say that heat is a form of energy ?

Ans: Take a vessel containing water in it. Keep a lid on it and heat. After some time you will observe the movement of lid up and down and this is due to steam. The energy which is required to change water into steam is heat, which is a form of energy. Hence heat is a form of energy.

3. What are the effects of heat ? Ans: Effects of heat :

1. Heat gives the capacity to work.2. Substances expand on heating.3. Heat converts water into vapour. This vapour can move an engine.

4. Air when heated becomes lighter. Hot air in houses leaves through ventilators.5. Micro-organisms in liquids like milk (and others) are destroyed on heating.6. Hen’s incubation supplies heat to the eggs which helps them to transform into

chicks.4. What is temperature ?

Ans: Heat and temperature are different. If heat is cause, temperature is its effect.Heat is measured in calories, Temperature is measured in degrees Centigrade (C) or degrees Fahrenheit (F). Centigrade is also called Celsius.

5. How can you say that heat and temperature are different ?

Ans: Take two beakers of different sizes and pour water upto the same level in both the beakers. There will be more water in big beaker and less water in small beaker. Heat them for 5 minutes with same sources. Measure their temperatures with thermometers. Water in big beaker shows less temperature than the water in small beaker. Why ? Though the heat supplied is same, water temperatures are different. It shows that heat and temperature are different. If heat is cause, temperature is its effect.

7.3 Transmission of heat

Important points :

Heat transfers from hotter objects to colder objects.

Heat transmits in 3 ways. i.e. 1. Conduction 2. Convection 3. Radiation.

Transfer of heat without the movement of molecules is called Conduction. It occurs in solids only.

Based on the transfer of heat, substances are categorised as 1. Conductors 2. Insulators

Substances which do not allow heat to pass through them are called Insulators.

Ex. Paper, Rubber, Wood.

Transfer of heat through the movement of molecules from one place to another is called Convection. It occurs in liquids and gasses.

Transfer of heat without any medium, from one place to another is called Radiation.

Evaluation1. What are the different ways of heat transmission ?

Ans: Heat transfers from hotter objects to colder objects. Heat transmits in three ways. They are 1. Conduction 2. Convection 3. Radiation.

2. What is conduction ?

Ans: Transfer of heat without the movement of molecules is called Conduction. It occurs in solids only.

3. What is convection ? Ans: Transfer of heat through the movement of molecules from one place to another is

called Convection. It occurs in liquids and gasses. 4. What is radiation ?

Ans: Transfer of heat without any medium, from one place to another is called Radiation.

5. How many types of substances are there based on transfer of heat ?

Ans: Based on the transfer of heat, substances are categorised into two types. 1. Conductors : Substances which allow heat to pass through them are called conductors. Ex. metals

2. Insulators: Substances which do not allow heat to pass through them are called Insulators. Ex. Paper, Rubber, Wood.

Additional Activities :

Take two tins and apply black colour to one of them. Pour equal quantity of water in those two tins and note the temperature. Temperature shows equal readings. Keep them in sun for sometime and note their temperatures once again.

You will observe that temperature in black coloured tin is more than the other one. What is the reason for that ?

Unit – 8NATURAL RESOURCES

Let us know about water and air. Natural Resources are the resources that are naturally available in the nature. Water and air are the most important natural resources. Water :

Water constitutes 70% of our earth’s surface. It is in the form of sea, river, lake, pond and as moisture (water vapour) in the atmosphere. Nearly 97% of water is in seas, oceans, which is not suitable for drinking purpose. Remaining 3% is fresh water. Of this fresh water, 2% is in the polar regions in the form of ice. Only the remaining 1% of water is suitable for our consumption (usage).

8.1. Nature of waterWater is the most important requirement for the sustenance of living organisms.

Water is available to us in three different forms namely solid, liquid and gas. Pure water is colourless, tasteless and odourless. Water changes into vapour, becomes dense and reaches the earth as rain. Less rainfall/no rainfall results in drought. High rainfall results in floods.8.1.1 Importance of water :

Water is the main factor responsible for life on earth. Water is useful for metabolic activities in living organisms, agriculture/irrigation, constructions, transport, washing clothes, hydroelectricity, extinguishing the fire etc. We should know the importance of water, its properties, and methods of conservation and use it with commonsense. Other wise, countries may face water scarcity in course of time.8.1.2 Different states of water :

Water exists in three different states. It exists as ice in solid state, water in liquid state, and as water vapour in gaseous state. Let us know how water is available in three states.Evaporation and condensation :

Water sources like lakes, ponds and wells are present in many places. In summer, the level of these sources get reduced and some of them get totally dried up. What happened to this water during summer?

Activity :- Take a plate, pour 5ml (1 teaspoon) of water and place this plate outside. Observe the water in the plate after 2 or 3 hours. Is there water in the plate? What happened to the water? When the plate is placed outside, it became water vapour and entered the air.

In this way, the water in seas, lakes and rivers continuously enter air. This is called moisture in air or humidity. This process in which water changes into vapour is called Evaporation.

The process of conversion of water into water vapour is called evaporation.

The volume of liquid which transformed into vapour in one second is called rate of evaporation.

Activity - 1 :- Take 3 plates, pour 25ml of water in each plate. Place one plate in sun, second plate under a fan and the third one at a place where fan is not there. After half an hour, pour the water from each plate into three separate glasses with equal volume and observe the difference. If there is any difference, discuss the reasons. Do other liquids also evaporate like water ?

Activity - 2 :- Collect six small, equally sized (25ml) injection bottles with lid, six saucer like plates and a funnel. With the help of funnel, fill the first bottle with petrol, second bottle with alcohol, third bottle with kerosene, fourth bottle with water, fifth bottle with ground nut oil and sixth bottle with palm oil. Pour the liquids in separate plates. Keep the plates at one place for half an hour. Now pour the liquids into the bottles again. Check the level of liquid in each bottle. In which bottle is the level of liquid high and in which it is low. Note down in the note book. Discuss which one has evaporated more and which one has evaporated less.

Activity - 3 :1. Repeat the above activity with available other liquids also.2. Conduct the same experiment in different places under the fan, outside in the

open area, in the shade. Record the results and discuss.3. Repeat the same experiment in the morning, afternoon and evening. Record the

results and discuss the reasons for differences.

Rate of evaporation differs from liquid to liquid : Rate of evaporation differs with place and time

Liquids like petrol, alcohol evaporate soon and liquids like water and oil evaporate late.

What happens to water that evaporated into air ?Activity :- Take a kettle. Pour one glass of water in it and heat it on a stove.

Measure the temperature with a thermometer when the liquid is boiling. You will observe that it is nearly 1000C.

When water vapour is coming out through the mouth of the kettle place a steel plate across the passage of water vapour, at a height of 5 cm. Pour some water in the plate. Observe the bottom of the plate where water vapour touches the plate. You will find drops of water. With this we could understand that when water vapour is cooled, it becomes water.

In the same manner, water evaporates into air, rises up and form clouds. When cold air comes in contact with the clouds, these clouds change into water drops. This process is called Condensation.

Condensation is changing of water vapour into water by cooling or Condensation is the process in which water vapour(gas) cools to form water(liquid).

Activity :- If you have a refrigerator in your home, take out a cold water bottle. Keep it outside and observe or pour cold water or ice cubes or ice cream in a glass, place it on the table and observe for two minutes. We observe droplets of water on the (outside) walls of the glass. From where did they come ? The water vapour in the atmosphere got condensed due to the coldness of glass and formed droplets of water.

It is because of this condensation that we get rains and rivers are flowing. These water sources are meeting the needs of life forms. Ex. Godavari and Krishna rivers.

Melting :- In Northern India, the ice present on the Himalayas is melting to form water and is flowing as rivers. This water is used by the people living on the banks of the rivers eg. Ganges river. In the same manner the ice in the polar regions also melts and reaches seas. This change of ice into water is called Melting.

The process in which ice is changed into water is called meltingSolidification :

Activity :- Mix a few pieces of ice with salt in a beaker. Fill a glass test-tube with cold water and place it in the pieces of ice. Keep it aside for half an hour and then observe the test-tube Take out the test-tube and observe . The water in the test-tube solidifies. How did this happen? A mixture of ice and salt is called solidification mixture or iced brine or ice-water mixture. It absorbs the temperature of the test-tube. Then the temperature of the water is reduced to 0C (Zero Degree Centigrade). The change of water into ice is called solidification. In the same way if the temperature increases from 0C the ice further changes into water.

Water changes into ice at 0CThe change of water into ice is called ‘Solidification’.

The temperature in places like Jammu, Kashmir, Himalayas in Northern India, North and South poles is less. They are covered with ice. A game called ‘skating’ is played in such places on ice.8.1.3 Water Cycle :

Can you imagine if water is not a renewable resource, what would have happened? There would have no life on earth. But due to the heat of the sun the water on earth, i.e. from plants (transpired), from animals, from various kinds of water sources evaporate in the form of water vapour into the environment and form clouds which cool and give rain. This is called Water Cycle.

Water on the earth rises up in the form of water vapour is cooled and return earth in the form of rain. This is called as water cycle.

or

Continuous exchange of water between land, sea and atmosphere is known as water cycle.

This water reaches the rivers, lakes etc. The remaining water flows into the sea. Water cycle is a life - giving source. 80 percent of rainfall in our country occurs from June to september.8.1.4 Floods :

Floods occur due to heavy rainfall. The over flow of river, streams, canals, drainage canals (drainage system) is due to these floods. Due to this fields are submerged, crops are damaged causing loss. Houses collapse. Huts are washed away. Alongwith the articles in the households, There is fear of animals and humans also being washed away. Normal life gets disrupted.

Famines occur if rains dont fall in due time in required amount. Living organisms doesn’t obtain water. Air becomes dry. Soil dries up and forms cracks due to lack of water. Rivers, ponds, lakes dry. Drought conditions mean crops do not grow due to lack of water. This results in dearth of food. Animals die due to lack of water and food. The generation of electricity in Hydel Projects ceases. There will be severe interruption to power supply. The differences in temperature bring about many changes in the environment. People migrate to places where sufficient food and water are available.

In severe conditions of drought and famine, people may fight among themselves for food and water.

In cities, sewage canals are not in order/regularized. So, roads are becoming water clogged even for scanty rains. We can avoid water scarcity if we can take such measures that this water is not wasted.

8.2 Water Pollution The presence of harmful substances in water is called water pollution and that

water is called polluted water.Water gets polluted in two ways :

1. Natural 2. ArtificialHow water is polluted naturally ?

Lakes and rivers are primary sources of water in rural and urban areas. Water in these sources get polluted due to washing of clothes, bathing of animals, swimming etc., Not only these, when cyclones, hailstorms, floods occur on a large scale, overflowing rivers, streams also pollute fresh water sources. In the same way when tsunamis occur, the salt water of the sea pollute fresh water sources on land.

Natural sources of fluorine are found in many habitats in our state. Here due to reduction in ground water reserves, more flourine is present in less water. This increases the concentration of flourine in water. 60 percent of habitats which pocess excess flouride content in our state are found in Ananthapur, Nalgonda, Karimnagar, Prakasam districts.

Drinking flourine water reduces growth and hardness of bones thus making them bend and causing them to curve. The teeth turn yellow color .This is called fluorosis.Artificial pollution of water :

1. Industrial Wastes:- The rise of industries is according to the needs of man. As these industries require water they are located nearer to the like sources of water lakes, rivers, and ponds Industrially discharged wastes contain poisonous chemicals, radioactive substances which are sent into water sources cause water-pollution. This is not only fatal to marine life but even human beings are prone to diseases by drinking this water. Some rivers in our country are being polluted due to industrial wastes. Eg:

River Yamuna, River Gowathi in Lucknow, River Hoogly in Calcutta, River Ganga in Kanpur, the rivers Godavari and Krishna in Andhra Pradesh.

2. Agricultural wastes:- (Due to manures and pesticides) The excessive use of manures, fungicides and pesticides in crops cause pollution of ground water, lakes, ponds, rivers and seas.

3. Due to crude oil:- Through out the world, special ships carrying crude oil (petroleum) tankers travel from one country to another by sea routes. If there is an accident this oil is released into the sea water and spreads as a layer for many kilometers on the sea water. This obstructs the entering of oxygen into the water and spoils the nature of water. The organisms living in water do not get enough oxygen and get decomposed. The color of water changes. The plants living under the surface of the water also die as sun light is not available to them, thus disturbing the equilibrium of the biosphere.

4. Due to slaughter houses:- Water is being polluted due to waste from slaughter houses, poultry farms, dairy farms which are released into the water thus polluting it. In water, the decomposers decompose these pollutants , thus releasing a bad odour. The colour of water changes.

5. Atomic Reactors:- Wastes discharged from these atomic reactors should be buried underground are thrown into the sea. The radiations from these prove fatal to humans, animals and plants making them prone to long standing ill-health.Waste Water :

The water used in households, water from industries, hospitals, offices, hotels release used water. In the same way, the water collected on roads and canals due to rain, the water flowing from roof tops contain harmful substances. This is called waste water. This waste water should be recycled or otherwise used for other purposes.Water Shortage :

Almost 42 percent of land has lost its fertility, thus turning it into a waste land. The ground water in 548 mandals out of 1104 mandals in our state has reduced below 10 meters. These areas are prone to serve shortage of water.

We are using 58 percent of ground water available to us. This is very high. The usage of more than 40 percent should be termed as water shortage. There is supply of drinking water in almost 90 percent of all places in our state. But the places having sufficient water is only 40 percent. Every year 7 to 8 percent of bore wells are getting dried up.

Man is responsible for the reason of drought conditions and water shortage is mainly due to insufficient plant growth. Drought situations are due to irregular distribution of water, reckless deforestation, unscientific raising of crops.

Harvesting of Rain water :

If villagers take up the activity of sludge removal in tanks, more water can be stored in them. Government should take up the renovation of lakes/tanks from time to time.

Groundwater increases if check-dams are built over rivers, streams and riverets. This water can be used for all purposes.

The rain water which flows from roof tops can be diverted into the surroundings of the house, into a pit or a big tank which can be used for few days.

Important Points :

Water is available in three forms – as ice in solid form, as water in liquid from and as water vapour in gaseous form.

The volume of liquid which changed into vapour in one second is known as rate of evaporation.

Water vapour changed into water when cooled is called condensation. The transformation (change) of ice into water is called as melting. The change of water into ice is called as solidification. The rising up of water on earth into atmosphere , forming clouds getting cooled

and returning to earth in the form of rain is called water cycle. Floods occur due to heavy rainfall. Famines occur if rainfall is scanty and do not occur in its due time. The addition of harmful substances in water is called water pollution. Water is polluted in two ways : 1. Naturally 2. Artificially.

EvaluationI Answer the following questions :

1. Write the importance of water.2. 70% of the earth is covered with water. Yet what is the cause for shortage of

water ?3. The evaporation of water in a plate kept outside the house is more than that kept

inside the house. What is the reason?4. What is water pollution ? Write four causes of water pollution.5. Write two precautions to be taken to prevent water pollution?6. Write the names of 4 rivers being affected by pollution?7. Write any 3 industries which cause water pollution?8. Water droplets are found on a bottle of cold water taken out from a fridge. What

is the reason?

II Fill in the blanks :1. Water constitutes ____________________ percent of earth.2. The change of water into water vapour is called ____________________ .3. The release of water vapour by plants is called ____________________ . 4. The change of water vapour into water is called ____________________ .5. The change of water into ice is called ____________________ .7. The rate of evaporation of water outside the house is ____________________

than that which is inside.8. Pure water does not have colour, ____________________ ,

____________________ .9. Water rising up to the atmosphere and again returning to earth is called

____________________ .10. Among Kerosene, and petrol ____________________ has more rate of

evaporation.11. The mixture of ice and salt is called ____________________ .

8.3 AirThe air cover of the earth extends upto 700 kms. from its surface. This air cover

is known as atmosphere. Atmosphere contains 78% Nitrogen and 21% Oxygen Apart from these gases, the atmosphere contains carbondioxide, hydrogen, inert gases, dust particles etc. Air is very essential for all living beings. Just imagine the non existence

of air? Did you see air? No. We cannot see air but we can experience it by the rustling of leaves on trees, when leaves and paper get blown and when it touches our body. Slow moving air causes coolness. In the previous class we have learnt that air is everywhere. Now we shall learn some more aspects of air. 8.3.1 Components of Air :

Air is not a single substance. It consists of Nitrogen, Oxygen, Carbondioxide, Water vapor along with inert gases like helium, neon etc. It also consists of dust particles and smoke. Therefore air is called a mixture.To demonstrate carbondioxide is present in the air : Let’s do :

Collect Lime used in betel leaves, a glass, water and a saucer. 1. Take a glass of water, add some lime to it and stir well. Leave it aside for

about two hours. Afterwards transfer the settled water (lime water) on the surface into a saucer. Keep this aside for about half an hour and then observe. A white layer is formed on the lime water. The reason for this is carbondioxide. This demonstrates that air contains carbondioxide.

2. Take lime water in another glass, blow air into it with the help of a straw. What happens? The colorless liquid turns into white isn’t it ! What is the reason for this? The carbondioxide from the air blown turns the liquid into white.

Lime water means calcium hydroxide. This reacts with carbondioxide forming a salt calcium carbonate. Due to this process the lime water turns into white.

Air contains carbondioxide

To demonstrate that air contains water vapor :

Take an ice cream from an ice cream vendor. Break it into pieces and fill them in a dry glass. Place this glass on the table. Observe on the surface of the glass after some time. Did you observe any droplets of water? How did they appear? The water vapor in the air turn into droplets of water on coming in contact with the coolness of ice cream. This proves the presence of water vapor in the air. The same can be observed in a glass filled with cold water, a cold water bottle taken out from the refrigerator and kept on the table and a cup of ice cream kept side for some time.

Air contains water vapor8.3.2 Air has weight :

Activity :- Collect stick of a broom, thread, alpin, two balloons of equal size.Make a hole in the middle of a stick of a broom. Make two holes at an equal

distance from the middle point of the broom stick. Introduce a thread from the middle hole of the broom stick and suspend it freely.

Tie two balloons blown with air with equal volume. The broom stick must be horizontal. Make a tiny hole to one balloon with the help of a pin on one side. The air goes out and the broom stick with the punctured balloon goes up showing that the balloon which has air in it has more weight Fig. 8.3.

Air has weightAir exerts upward pressure :

You enjoy flying kites during Sankranthi holidays. In the same way we watch with interest aeroplanes, kites and hot air balloons flying in the air. What holds these

heavy things high up in the air? In the same way what lifts a light weight paper and leaves ?Activity :

Fill the glass tumbler completely with water upto the brim. Place the paper over it and invert the glass with the paper. Did the paper fall ? No ! Why did this happen ?

It is because the air from below is exerting pressure and this pressure is supporting the paper. This is called upward pressure of air.Air has downward pressure :

You know what happens when bottles and tins filled with water get punctured. The leakage of water from the holes show that air exerts pressure on the surface of water. It is air that releases water out from a siphon pump.Activity :

Collect a glass beaker, a glass tumbler, a colored plastic ball and water.Fill the glass beaker with more than half its capacity. Immerse the ball in the

beaker of water. It floats on the water. Invert the glass tumbler on the ball and observe. What do you observe ? The ball goes down to the bottom along with the glass tumbler. The rim of the glass tumbler remains on the surface itself. This shows that the air in the glass thrusts the water downwards.

Air has downwards pressureAir exerts side ward pressure :Activity :

Collect a plastic mineral water bottle along with its cap and some hot water (50C to 60C).

Pour hot water in the bottle. Close it and shake it on all sides. Open it, throw away the water, recap it, place it on a table and observe.

The sides of the bottle are pulled inwards. This demonstrates that air has sideward pressure.

Air has sideward pressure

8.3.3 Measuring atmospheric pressure :Air has weight. Any substance that has weight exerts pressure. Air exerts

pressure on earth’s surface. This pressure is called ‘ Atmospheric pressure ’. Barometer is used to measure the atmospheric pressure. There are many kinds of barometers in usage. Cistern barometer is one among them.Construction of barometer :

Collect a thick walled glass tube of one meter long, 5 cm diameter, closed at one end, 250 ml trough, 2 kgs Mercury, a pair of gloves as shown in the diagram (8.6). Wear a pair of gloves to two hands and fill the trough with some mercury. Pour pure mercury in the glass tube. Close the open end of the tube with your thumb and move the tube up and down, so that the air bubbles, will be removed. Place the tube in a trough containing mercury and remove your thumb. A portion of mercury in the tube falls down into the trough. Mercury in the tube stands still at a certain height of centimeters. This is called Mercury column. Vacuum is formed above the surface of mercury column. This is called Torricelli Vacuum. The height of mercury column near the sea-level will be 76 cms. This is called normal atmospheric pressure.Working of the barometer :

The pressure exerted by the atmosphere on the surface of the mercury in the trough is equal to the pressure exerted at the same level in the tube. That’s why the height of 76 cm of mercury column is equal to the atmospheric pressure. Because of this the height of mercury is used in measuring the atmospheric pressure. This barometer is not convenient to carry from place to place.

8.3.4 Aneroid Barometer :This is a portable barometer because it does not use any liquid. This is used to

measure the atmospheric pressure in inflated tyres of vehicles. Atmospheric pressure is measured in Millibars.

Aneroid Barometer is used to measure the air pressure in inflated vehicle tyres.Construction of Aneroid Barometer :

(a) As shown in the figure, take a metal box (B), arrange a diaphragm (D) on it and see that there is comparatively lower pressure. As shown in the figure, arrange a tube which has (teethed tube) (T) in the middle of the diaphragm. Its teeth must be arranged with in the teeth of the wheel (W). Arrange a pointer (P) to the wheel. Arrange a curve scale (S) above the pointer.

(b) Working :- The pointer moves when there is a difference in the atmospheric pressure. If there is a decrease in pressure, the diaphragm, is pushed up. Pointer moves in anti clockwise direction. If the atmospheric pressure increases, the diaphragm pushes into the box. Pointer moves in clockwise direction along with the wheel. This indicates increase in atmospheric pressure.Uses of Barometer :

As air has weight, the pressure increases with the increase in length of air pillar and increase density of air. In the same manner, as we go up the sea level, the length of the air pillar decreases. i.e., pressure decreases. As we go down the sea level, air pillar increases i.e., pressure increases. With this (barometer) we can identity the height at which we are from the sea level and the depth at which we are below the sea level. As we go up the sea level, for every 272.7 meters height, there will be a decrease of 2.54 cm. pressure. In the sea level, for every 272.7 meters depth, there will be an increase of 2.54 cm. pressure.

The sudden quick drop in the mercury level of the barometer indicates a storm. If there is a slow decrease in the level of mercury, it indicates coming rain. This way, weather forecasting department is able to identify the changes in the atmosphere in time and issue danger warnings.

With the help of Barometer, we can forecast rain and storm and can identify height and depth from sea-level

Air pressure helps us in many ways. Let us know its applications.Air pressure helps us to drink water, fruit juice using a straw, to pull water using

siphon system, to draw medicine drops by fillers. It is used in tyres of motor vehicles, in the balls that are used to play.Air Pollution Causes & Control

Pollution is mainly of four types 1. Air pollution 2. Water pollution 3. Land pollution 4. Noise Pollution

Now let us learn about Air Pollution.In the previous class we have learnt about air, its constituents and its pollution .

At present, keeping in view the amount of pollution in the air it is very essential to know

the measures to control air pollution. According to the survey of Pollution Control Board it is estimated that the rate of pollution is 35 percent more than the estimated amount.

The presence of harmful substances in the air is called air pollution.Indian Government has set up the Central Pollution Control Board at National

level and the State Government has set up the Andhra Pradesh Pollution Control Board. Presently, Compressed Natural Gas (CNG) is used. By using this there is no fear about the factors affecting pollution except Carbondioxide.

Scientists are also warning that as a result of global warming, the ice at polar regions will melt, and as a result, the sea water level will increase and there will be a danger of coastal region getting submerged.

(a) Factors affecting pollution :(i) Carbonmonoxide :- Carbonmonoxide is evolved if the fuel is not used

completely. If there is sufficient supply of oxygen, Carbondioxide is evolved instead of Carbonmonoxide Carbonmonoxide is harmful than carbondioxide. This is emitted from electricity generating projects which depend on coal and when fuel in vehicles does not burn completely.

(ii) Sulphurdioxides:- Fossil fuels contain sulphur. On combustion, they form sulphurdioxide forming acid rains. Sulphurdioxide and sulphurtrioxide are released when volcanoes erupt, when fuels like petroleum, diesel and kerosene burn, when ores containing sulphur are burnt in metallurgy.

(iii) Nitrogen oxides:- Nitrogen oxides like Nitrogendioxide, Nitrogentrioxide, Nitric oxide also lead to acid rains. Nitrogen oxides evolve due to intense temperature in the environment. Acid rains increase the acidity of soil, plants are destroyed, aquatic beings lose the lives and water pollution increases.

(iv) Dust, smoke:- The suspended particles in air like microscopic dust particles are emitted from vehicles and industries. They cause lung diseases. Dust on leaves interupts photosynthesis. These are called SPM (Suspended Particulate Matter).

(b) Reasons for pollution :(i) Vehicles :- Vehicles which run on diesel and petrol emit gases which contains

pollutants like Sulphur. Black smoke is ejected when the fuel does not burn completely which contains carbon monoxide and sulphur, carbon related ash.

(ii) Thermal Power Plants :- Coal is used as fuel in these plants. Coal contains sulphur substances. Emission of sulphurdioxide, carbonmonoxide and carbondioxide takes place on combustion of coal. Dust is also released due to incomplete combustion of fuels.

(iii) Industries :- Many industries release chemical substances. The sulphur and nitrogen oxides released by industries are the cause for acid rains. The beauty of the historic Taj Mahal is also marred by the oxides of sulphur and nitrogen released. By oil refineries located nearby. In the same way, the dust and smoke released from factories is the cause for pollution.

Air pollution is responsible for deadly diseases like Asthma, T.B., and Cancer.(iv) Homes :- Smoking, Smoke emitted from kitchen, chemicals used for cleaning,

insecticides, gases evolved from damages are responsible for pollution. Smoking is banned in many countries.

(v) Other reasons :- Ozone layer is depleted by the gases emitted from refrigerators, air conditioners used by man.

In addition to disposal of waste, dust evolved during winnowing, dust from concrete preparation, pollution is also caused due to natural phenomena like Volcanoes, Earthquakes, Storms. etc.

Measures to control pollution :1. The vehicles should be constructed in such a way that the fuel used in it is

completely combusted.2. We can prevent pollution using Compressed Natural Gas.(CNG).3. Using petrol without lead.4. Refinement of polluted air released from factories.5. Using hydroelectric stations, solar energy, wind energy, hydrogen as fuel instead

of thermal power plants.6. The quantity of Oxygen in air is reduced due to deforestation. Deforestation

should be stopped and afforestation should be promoted.7. Nuclear tests & tragedies : With a desire to progress, many countries are

conducting nuclear tests. Because of nuclear tests radiation are nuclear wastes released. This radiation is putting people, plants in danger. Air craft accidents, space accidents are also causing air pollution.

8. Sound pollution: Sound more than the audible range is also a cause for atmospheric pollution.

Green House effect (Global Warming) :Earth absorbs some part of radiation from earth and emits some part of it into the

atmosphere. Gases like carbon-di-oxide, methane, ozone, water vapor which are known as green house gases, absorb the heat reflected by the earth. As a result, atmosphere gets heated up. As there is enormous release of gases like carbon dioxide into the atmosphere, earth is absorbing more heat of sun, and is getting heated. This is known as the green house effect or global warming. Important Points :

The air surrounding the earth is called atmosphere. Nitrogen, Carbondioxide, Water vapour, inert gases like helium, neon, dust,

particles are present in air. Air has weight. Air exerts pressure. Mercury barometer and aneroid barometer are used to measure air pressure. The presence of undesirable, harmful elements in the air is called air pollution. Gases like carbondioxide, methane, ozone present in the air absorb more heat

making the earth warm. This is called global warming.

EvaluationI Answer the following questions :

1. What is atmosphere ?2. Does air occupy space ? or not ? How can you till ?3. Air is a mixture. How do you explain ?

4. How can we prove the presence of carbon dioxide in air ?5. How can you say that water vapor is present in air. Give two examples.6. Does air has weight ? prove it.7. Explain the experiment that air has upward pressure ?8. Write down the experiment that proves air has downward pressure.9. Does air has side ward pressure ? Give two examples.

10. Give applications of air pressure.11. How is air pressure measured ? Explain the changes that occur. When we go up

and down the sea level.12. Explain the construction of mercury barometer. Draw diagram.13. Draw a diagram of a aneroid barometer and write its construction.14. What are the uses of barometer ?15. Name three air pollutants and give reasons.16. What is global warming ?17. What measures can be taken to prevent air pollution.

II Fill in the blanks :1. The presence of undesirable, harmful substances in the air is called

______________ .2. Air occupies _______________ .3. Oxygen and Nitrogen are present in ______________ ratio in air.4. The gas present in highest proportion in air is ______________ .5. Lime water is turned into white colour by ______________ .6. Water droplets formed around the glass with cold water. This is because of

______________.7. ______________ is present more in industrial areas.8. Aeroplanes, hot air ballons are able to fly in air due to ______________.9. Air should exert ______________ pressure to make water pour down from a hole

in the bottle.10. The instrument used to measure air pressure is called ______________.11. A barometer prepared without any liquid is known as______________.12. Atmosphere pressure at sea level is ______________ cm.13. As we move up the sea level, air pressure ______________.14. As we move down the sea level, air pressure ______________ .

15. The vacuum in mercury barometer is called ______________ vaccum.Unit- 9

HEALTH - HYGIENE - SAFETY AND FIRST AID9.1 Maintaining Good Health

“Health is wealth” is a popular saying. We should understand the importance of health in our life. World Health Organisation defined health as :

Health is a state of (complete) physical, mental and social well-being of a person.

Besides physical health, surroundings also play an important role in keeping us healthy. Taking proper food helps our body perform different metabolic activities properly. This implies that (it means that) there is a relationship between the food we take and our health.

We take rice, dal, chapathi, bread, vegetables, leafy vegetables, ghee, oil, milk, eggs, grains, meat, fish etc. as our food every day. We can divide these food substances in the following way.

1. Carbohydrates :- Food substances like rice, chapathi and bread are rich in carbohydrates. Carbohydrates give energy to our body.

2. Proteins :- Dal, meat, fish, milk, eggs are rich in proteins. Proteins help in growth and body building.

3. Fats :- Fats are present in ghee and oils. Fats give energy to our body.4. Minerals :- Minerals are present in the food we take. They are present in leafy

vegetables, vegetables, pulses, eggs, meat, fish and milk. Minerals like calcium, phosphorus make our teeth and bones strong; iron helps in the formation of haemoglobin and iodine helps in the proper functioning of brain.

5. Vitamins :- Vitamins are part of our food. They are present in leafy vegetables, vegetables, milk, eggs, fish, meat, and pulses. Vitamins protect our body from diseases.

6. Fibres :- Vegetables, leafy vegetables, grains, fruits are rich sources of fibre. They avoid constipation.

7. Water :- We drink water frequently. Water is also available in the food we take. Water helps in the transportation of materials in our body.Balanced Diet :

The food which contains all the nutrients in appropriate quantities as required by the body is called “ balanced diet. ”

In a balanced diet, energy giving foods and body building foods are in required quantities.

If we arrange the components of balanced diet like a pyramid in the order of their importance, it looks as apyramid Fig. 9.1

If we do not take nutrients as mentioned in the balanced diet pyramid, our body will be affected with deficiency disorders, diseases.

Important points : Health is the physical, mental and social well being of a person.- W.H.O Balanced diet is that which consists of Carbohydrates, Proteins, Fats, Vitamins,

Minerals, Fibre, water in a definite Wroportion.

EvaluationI Answer the following questions :

1. What is health ?2. What are the components of balanced diet ?3. How are minerals helpful to our body ?

II Match the following :1. Rice ( ) (a) avoids constipation.2. Oil ( ) (b) proteins3. Pulses ( ) (c) carbohydrates

4. Fibre ( ) (d) fatsIII Suggested Activity :

Make a list of food items you ate in a week; divide them as components of balanced diet.

9.2 Personal HygieneThe main objective of personal hygiene is to protect our body from harmful

microbes and toxins, there by protecting ourselves from diseases.Personal hygiene can be practised in the following ways.

1. Brush your teeth every morning as soon as you wake up, after taking food and before going to bed at night.

2. Defecate every day. After defecating, wash your hands and legs with soap.3. Take bath everyday with clean water.4. Wash your hands with soap before taking food.5. Take head bath at least twice a week.6. Cut your nails regularly.7. Wear clean washed clothes every day.8. Wear foot to avoid the entry of microbes into your body.9. Avoid uncovered food, rotten and stale food.

Person without personal hygiene is prove to various diseasesSkin diseases – Protection :

Skin covers our body. It is like a protective shield. As it is the outer membrane of our body, it is affected with different weather conditions and micro organisms. Sometimes disease causing micro organisms enter the skin and cause skin diseases. Common skin diseases observed in children and adults :

1. Itching 2. Measles 3. Eczema4. Pellagra 5. Acne 6. Scabies 7. Ring worm 8. Psoriasis

Observe the pictures showing various skin diseases.Prevention of skin diseases :

1. Take bath everyday and wear clean washed clothes.2. Keep your skin clean and gentle. By cleaning your skin with soap or flour

mixture, it is freed from dirt and disease causing microbes.3. During winter skin becomes dry & rough due to cracks. To prevent this, apply oil,

Vaseline.4. Diseases like scabies, ring worm are contagious. The clothes used by persons

affected with these diseases should not be used by others.5. Do not use the soap used by others.6. The sweat pores in the skin are closed by applying excess beauty creams. This

prevents the normal functioning of skin. Therefore, use them sparingly. By taking the above measures one can keep skin clean and healthy.

Eye - Care :You have learnt about the cleanliness of eyes in the previous classes. Now, let us

learn some more ways of taking care of eyes.1. Do not look directly at sun, strong light and light produced during welding,

thundering. Do not look at sun during an eclipse.2. Read and write in sufficient light. Do not watch television for too long.

3. Eat leafy vegetables, carrot, papaya, mangoes.4. Vitamin - A is required for healthy eyes and to prevent diseases like night

blindness. Therefore, infants should be compulsorily fed with mother’s milk. Mother’s milk contains large amounts of Vitamin - A.

5. Vitamin - A, doses are available in the primary health centres. This should be administred to children once in six months.

6. Stay away / Keep distances from the people suffering from conjunctivitis. 7. If you suffer from watery / teary eyes and blurred vision, consult an eye specialist

(opthalmologist) immediately.

Dental - Care (Taking Care of Teeth) : Healthy teeth play a prominent role in our health.

Teeth play an important role in tearing, grinding and chewing food. Teeth are formed during childhood. Therefore, it is essential to take nutritious

food at this stage. Milk, substances containing calcium should be taken in large quantities.Let us now learn some more ways of taking care of our teeth :1. Clean your mouth after taking food. Otherwise food particles remain in the gaps

between the teeth. Bacteria act on these food particles and cause bad breath and tooth decay.

2. Do not use pins, needles to remove food particles between the teeth.3. Consumption of more chocolates, sweets, icecreams causes tooth decay.

Therefore, eat them sparingly. Whenever you eat them, rinse your mouth.

4. Presence of fluorine in drinking water damage teeth by forming yellow streaks on teeth. Avoid water containing fluorine for drinking purpose.

5. Deficiency of Vitamin - C leads to swelling and bleeding of gums. Citrus fruits contain more Vitamin - C. Consume them regularly.

6. If you have any teeth problems like arrangement of teeth etc., and to have more information on dental care, consult a dentist, and take his / her advice or treatment.

Community Hygiene :Along with personal hygiene, cleanliness of our surroundings is also necessary to

maintain community healthy. Therefore, it is our responsibility to keep our surroundings neat and clean.

Community partnership is essential in conserving the environment. Panchayats and Municipalities provide us many facilities. We should use them with commonsense.

Water should not be allowed to stagnate. Sewage water should be disposed properly. Drains should be built to avoid stagnation. If there is stagnant water, kerosene or phenol should be sprayed to prevent the growth of mosquitoes and their larvae (to prevent the breeding of mosquitoes).

Measures like keeping the roads clean without garbage heaps, sprinkling bleaching powder along the roads should be taken to keep the surroundings clean.

Defecation and urination should not be done in public places. Every house should have toilet. Garbage should be dropped only in the garbage bins. These bins should be emptied frequently and garbage should be disposed far away from the village.

Community has to take initiation to prevent the prevalence of epidemics / contagious diseases during certain specific climatic conditions. Vaccinations should be administered to everybody. Smoking (Smoking in public) should be prohibited. Trees should be grown in open places and along the sides of roads.

Bathing and washing clothes near wells and borewells should not be allowed. Water should not be let stagnate at such places.

Washing cattle, immersing coloured idols with poisonous chemicals, washing vehicles, defecating and urinating in lakes and streams should be avoided. Waste Management :

In our everyday life we perform various activities. To perform these activities we use different materials. From these materials, some waste products are formed. If these waste products keep on increasing, they cause harm to us and also to our environment.

Using materials and things more than the requirement and inability to use the available things properly is a problem. This also results in increasing the production of waste.

You must have observed the waste produced from your homeWaste produced from household

Reduce - Reuse - Recycle of waste :We should try to reduce the production of waste from our daily life activities. We

can reuse some of the waste materials by making some minor changes and repairs to them. Some of them can be recycled. We can protect our environment by reducing, reusing and recycling waste.

Management of solid waste :

Waste produced from houses, canteens, hotels like waste food materials, shedded leaves and garbage can be changed into compost.Changing garbage / waste into compost :

When soil and garbage / waste are put in a pit layer by layer and water is sprinkled every day, after some days the waste decays due to the action of microorganisms and compost is formed. This can be used as manure to plants.Advantages of (using) compost :

1. The organic material present in garbage changes into manure, which is required by plants and crops.

2. Usage of chemical fertilizers is reduced, by using compost thus reducing the soil and water pollution.

3. Removing the garbage in the surroundings will keep our surroundings clean. Vermicompost :

Now a days farmers are yielding good results by using vermicompost, the compost prepared by using earthworms.

Earthworm is one of the animals which is helpful to us. It is called as farmer’s friend. Using vermicompost in place of chemical fertilizers will make the soil more fertile. Preparation :

Make a pit in the ground. In the lower portion of the pit, put fibre. On the fibre layer, keep organic waste and cow dung layer by layer. More number of earthworms are to be kept in the upper layers. The physical, chemical and biological activities of earthworms change the waste into manure. They degrade waste and improve soil aeration. They act as crushers by making the waste upside down. They act as mixers by mixing the soil. They take the organic waste as food. After this food is digested, they excrete. This excreta contains nitrogenous substances. This is called as vermicompost.

Using vermicompost for plants and crops will not only increase yield but also decreases expenditure. It increases the fertility of soil. It reduces the useless waste at home.Important points :

The main objective of personal hygiene is to prevent the entry of harmful microbes and toxins into the body there by preventing diseases.

We can maintain personal hygiene by practising good habits. Itching, measles, eczema, pellagra, pimples, scabies, ringworm, psoriasis are the

skin diseases usually observed in children and adults. We can keep our eyes healthy by taking foods and fruits containing Vitamin - A. We can be healthy if we have healthy teeth. Environmental protection is everybody’s responsibility. We can reduce the waste matter / materials from our surroundings by making

some changes to them and using again. The fertility of soil is increased and good yield can be obtained by using compost

and vermicompost.Evaluation

I Answer the following questions :1. Name some skin diseases.2. How will you take care of your eyes ? 3. What are the waste materials produced from houses ?4. Write the advantages of compost pit.5. Draw a labelled diagram of vermicompost making procedure.

II Fill in the blanks :1. Earthworm is known as ____________________ friend.2. Vitamin ___________ is required to prevent night blindness.3. Yellow streaks form on teeth because of __________________ present in water.4. To prevent the development of mosquitoes and larvae in sewage water

__________________________________ should be sprayed.III Project :

1. Arrange a compost pit in your school and prepare compost.2. Visit the streets, surroundings of your school and home to see if there are any

unhygienic conditions, analyse them and suggest appropriate measures to change them.

IV Suggested Activities :1. Conduct a quiz, elocution and painting competitions on the topic of

“Environmental Protection.”2. Prepare and display playcards on the topic “Environmental Protection”.

9.3 Safety - Protection - First Aid

An immediate treatment given to a person affected with an accident before taking the person to a doctor is known as first aid. This is done before taking the person to a doctor.

In the previous classes you have learnt about the first aid to be done to injuries, insect bites, scorpion bite, snake bite, dog bite etc. Now let us learn about some more methods of first aid for other accidents.

Fire Accidents – First Aid :

An accident which occurs due to fire is called a fire accident.

Fire accidents may take place due to kerosene, petrol, cooking gas, stove lamps, hot liquids, crackers or laboratories.

Negligence and carelessness are the main reasons for fire accidents. Fire accidents result in loss of property, people and harm the environment.

When a person catches fire in a fire accident, do not remove the victim’s clothes. Cover victims body with a thick blanket and roll on the ground. Cover the burnt portion with a wet cloth. Take the victim to a doctor immediately.

If skin is burnt in a fire accident, pour cold water. Wipe with a clean cloth and apply an ointment or cream like burnol.

Sun stroke - First Aid :

During summer the atmosphere is very hot and dry. Because of high temperature the functioning of body will be impaired. This condition is called Sun stroke. In this condition the skin becomes hot and dry. The victim suffers from head ache, giddiness, high temperature and cannot see properly.

Take the victim to a cool place, and loosen the clothes. Sponge the body with wet cloth and cover it with a wet cloth. See that the victim gets proper aeration. The body loses water and salts due to sun stroke. Give cold water and fruit juices. Rehydration solution should be given to the victims to replenish the lost water and salts.

Preparation of ORS (Oral Rehydration solution) : - Take cooled boiled water in a glass. Add 2 or 3 spoons of sugar and a pinch of salt to it. Stir it with a spoon. This solution is called ORS (Oral Rehydration Solution).

This ORS should be given to the patient frequently in little quantities to replenish lost salts and water. This solution should be prepared afresh every time. Stored ORS should not be given to the patient. Electric Shock – First Aid - Preventive measures :

The fluids, muscles and nerves in the body will be subjected to crisis due to electrical effect. This feeling is called Electric Shock.

The person who is affected with electric shock should be separated from the source (electricity) by using wooden things (stick).

The following measures should be taken to prevent electric shock.1. Use the electric appliances with care / caution.2. Switch off the electric appliances after using them.3. Do not touch electric appliances with wet hands and moist clothes.4. See that electrical appliances are not in the reach of children. Switch boards and

electrical wires should be arranged at a height not reachable to children.5. The house wiring and switch boards should be checked frequently and those

which are damaged should be replaced immediately.Drowning – First Aid : The following first aid should be given to protect a person drowned in water.

Bring the victim out of the water with the help of a stick / log, rope or other persons help. Lay the victim on his stomach. The person giving first aid should press on the back of the victim with two hands.Then place the victim’s body in an inclined position and press up and down in the chest region. This expels the water swallowed by the victim. Artificial respiration should be given if necessary.

Important Points : An immediate treatment given to a person affected with an accident is known as

first aid. Fire accidents result in loss of property, people and harm the environment. To replenish water and salts in the victim of sun stroke, oral rehydration solution

should be given. We should not touch electric appliances with wet hands and moist clothes. Artificial respiration should be given to a person drowned in water if necessary.

EvaluationI Answer the following questions :

1. What is meant by first aid ?2. What are the changes that take place in the body due to electric shock ?3. What should be done if skin is burnt in fire accident ?4. How will you save a person drowned in water ?

II Suggested Activities :1. Prepare oral rehydration solution at home.

Unit-10INFORMATION AND

COMMUNICATION TECHNOLOGY Today we are living in a modern world where various comforts are available.

Earlier these comforts were not available. In good olden days messages were sent by pigeons. It use to take long time to reach the destination. Contributions of scientists made the communication faster through newspapers, post and telegraph, telephones, radio, television, fax, computer, cell phones and satellites etc.

Information and Communication Technology is a branch of science which deals with utilization of computers and telecommunication for betterment of our day to day life.

Today computers are used in every walk of our life. Computer is a machine which works accurately and very fast. It can solve all sorts

of complicated problems in short time with accuracy. Man cannot do same work repeatedly with the same efficiency, where as the computer can do it any number of times and any length of time with same efficiency and accuracy. Computer can save lot of data and programmes in it. It can store the data and display it whenever we require itComputer is a machine that processes the data on mathematical or logical operations

Parts of computer 1. C.P.U 2. Monitor 3. Keyboard 4. Mouse

.

The main parts of a computer are C.P.U (Central Processing Unit), Monitor, Key Board and Mouse.

How does the computer work ?

Computer works on the principle input process output

The data and instructions given to the computer through input devices are processed in the Central Processing Unit (C.P.U) and results are displayed through the output devices.Input devices :

Input devices include Keyboard, Scanner, Microphone, Web Camera and Mouse etc.

Table 10.1 Input EquipmentSl. No. Input device Figure function1. Keyboard Instructs the

computer by typing the data.

2. Mouse It selects the item on the monitor,

it gives instructions

3. Scanner Scans the picture and saves in

computer.

4. Microphone It records the sound.

5. Web camera It records the scenes.

Processing :

Analyzing the data following the instructions and giving result is known asProcessing.

A group of commands used for processing is called “Computer Programming.”

C.P.U of computer understands/reads the instructions and processes the information. There are three units in C.P.U namely Control Unit (C.U), Memory Unit and Arithmetic Logic Unit (A.L.U). In C.P.U. the signals from input devices are analyzed by control unit.

These signals are stored temporarily in the memory unit. Analyzed signals ( data & commands) are sent to arithmetic logic unit and finds solutions for mathematical and logical problems. After completing the calculations results are sent to the output devices.Output devices :

The result of the analyzed data is shown on monitor or printer or speaker

Table 10.2 Output Devices:

Output device

1 Monitor Looks like television screen. One can see the data, graphs, pictures etc. on the screen.

2 Printer Device that transfers the data from computer to paper in print form.

3 Speaker The device through which sound is emitted

Uses of computer :

Now a days computers are used for various purposes. Train tickets can be booked on computers. In Hyderabad one can book tickets from Chennai to New Delhi. Money can be drawn from any bank other than the account holding bank. Computers made it possible to draw money from ATM (Automated Teller Machine) anywhere in India and at anytime. Different web sites on internet provides vast information. Governance and other activities are done quickly by using internet. One can send mails to friends and relatives in different places in few minutes through e-mail.

Communication has become fast because of computers and satellites. This is possible because of the speed, accuracy and the storage capacity of the computers. In the present world computers are inevitable. Computers are also used in different fields like industries, business, science, education, medicine, agriculture, governance, ordinance, weather, astrology, defence etc. There is no field where the computer is not used.

However faster and efficiently may the computer work, it cannot make it’s own decision. It obeys the instructions and commands given by man and works.Important points :

In ancient times man used pigeons to send messages. Information and Communication Technology is a branch of science which deals

with utilization of computers and telecommunication for betterment of our day to day life

The computer is a machine that processes the data on mathematical or logical operations

Computer works fast, accurately with out rest and stores a lot of information. It also displays the stored data whenever it is asked.

Computer works on the principle input-process-output. Key board, C.P.U (Central processing unit), monitor, and mouse are the main

parts of the computer. Keyboard, scanner, microphone, web camera and mouse etc. are some input

devices. A group of commands used for processing is called “computer programming” Control unit (C.U), Memory Unit, and Arithmetic Logic Unit (A.L.U) are the

main parts of C.P.U Monitor, printer and speaker etc. are output devices. World wide computers are used for various purposes. Computer works and obeys the instructions and commands given by man.

Evaluation

I Answer the following questions :1. Define “Information and communication Technology”.2. What is a computer ? 3. What is the importance of the computer?4. Explain how computer works.5. Write about any two input devices.6. Write about any two output devices.7. What is a computer programme?8. Write the uses of computer.

II Fill up the blanks :1. Computer is a ___________________ device.2. Data and commands are given to the computer through ________.3. The part of the computer which looks like television screen is _________.4. Printer and speakers are _______________ devices.5. The important part of computer is _____________.

III List out separately the input and output devices from the following :

(1) Keyboard (2) speakers (3) mouse (4) scanner (5) monitor

(6) microphone (7) printer (8) web camera.

Input devices :–––––––––––––––––––––––––––––––––––––––––––––––––––––––––

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Output devices : –––––––––––––––––––––––––––––––––––––––––––––––––––––––––

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