6$03/(Judy McDougall - Doc · PDF fileJudy McDougall. INDEX ... Practical investigation 5 145 ... This is why photosynthesis and respiration play a big role in the survival of most

Natural SciencesGrade 8

Textbook and Workbook

Santie du Plessis • Pikkie du ToitCarlien Fanoy • Lettie Fischer

Christiaan Geel • Natalie Janse van RensburgMarga Koelman • Patricia Lees-Rolfe

Judy McDougallSAMPLE

INDEXUnit Page

TERM 1 LIFE AND LIVING 13

Unit 1 PHOTOSYNTHESIS AND RESPIRATION 13

1.1 Introduction 13

1.2 Photosynthesis 13

1.2.1 Requirements 14

Activity 1 14

1.2.2 Products of photosynthesis 15

Practical investigation 1 17

Exercise 1 20

1.3 Respiration 22

Activity 2 23

1.3.1 Types of respiration 23


1.3.2 Comparison between photosynthesis and respiration 25

Exercise 2 26

Summary of Unit1 27

Mind maps of Unit 1 28

Unit 2 INTERACTION AND INTERDEPENDENCIES 29

2.1 Introduction to ecology 30

2.2 Ecosystems 30

Activity 3 32

Activity 4 33

2.3 Interdependency in ecosystems 34

2.3.1 Mutualism 34

2.3.2 Commensalism 35

2.3.3 Parasitism 35

Exercise 3 36

2.4 Feeding relationships 38

2.4.1 Producers and consumers 38

2.4.2 Herbivores 38

2.4.3 Carnivores 40

2.4.3.1 Predators 40

2.4.3.2 Scavengers 41

2.4.3.3 Insectivores 41

2.4.4 Omnivores 41

2.4.5 Detritivores 42

2.4.6 Decomposers 42

Activity 5 43

Exercise 4 44

2.5 Energy flow 47

2.5.1 Food chain 47

Exercise 5 49

2.5.2 Food webs 51

Activity 6 53

2.5.3 Energy pyramids 54

Activity 7 54

Exercise 6 55

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2.6 Ecological balance 58

Activity 8 59

2.7 Adaptations 59

2.7.1 Plants 59

2.7.1.1 Xerophytes 60

2.7.1.2 Hydrophytes 62

2.7.2 Animals 63

2.7.2.1 Camel 64

2.7.2.2 Polar bear 65

2.7.2.3 Predators 66

Activity 9 67

2.7.3 Camouflage and mimicry 68

2.8 Conservation of the ecosystem 69

Exercise 7 70

Summary of Unit 2 76


Unit 3 MICROORGANISMS 83

3.1 Introduction 83

Activity 10 84

3.2 Types of microorganisms 84

3.2.1 Bacteria 84

3.2.2 Viruses 85

3.2.3 Fungi 85

3.2.4 Algae 85

3.2.5 Protozoa 86

Activity 11 86

3.3 Harmful microorganisms 86

3.3.1 Diseases 86

Activity 12 87

3.3.2 Where harmful microorganisms are found 87

3.3.3 Waterborne diseases 88

3.3.4 Prevention of spread 88

3.3.5 Scientific contributions 89

Activity 13 89


3.4 Useful microorganisms 90

3.4.1 Decomposers 90

3.4.2 Water purification 90

3.4.3 Digestive system 90

3.4.4 Production 91

Activity 14 91

Exercise 8 91



Glossary 96

Term test 99

TERM 2 MATTER AND MATERIALS 113

Unit 1 ATOMS 113

1.1 Particles 113

Practical task 1 115

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Exercise 9 115

1.2 Elements 117

1.3 Compounds 118

1.3.1 Forces between particles 119

Exercise 10 120


1.3.2 Decomposition 124


1.4 Mixtures 126

Exercise 11 127



Unit 2 PARTICLE MODEL OF MATTER 131

2.1 Particles 131

2.2 Models 131

2.3 States of matter 132

2.4 Diffusion 133



2.5 Physical changes 134


Exercise 12 137

2.6 Density 142

2.6.1 Mass and volume 142

2.6.2 Density of materials 143




Project 147

2.6.3 Applications 147

2.7 Expansion and contraction of materials 148

Practical investigation (demonstration) 8 148

Activity 15 149

2.8 Pressure 149



Exercise 13 151



Unit 3 CHEMICAL REACTIONS 159

3.1 Reactions 159



3.2 Indigenous knowledge systems 162

3.3 Careers 162

Exercise 14 163



Glossary 169

Term test 171

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TERN 3 ENERGY AND CHANGE 179

Unit 1 STATIC ELECTRICITY 179

1.1 Friction 179

1.2 Forces between charges 180

1.3 Polarisation 180


1.4 Safety 183

Exercise 15 183



Unit 2 ENERGY TRANSFER IN ELECTRIC SYSTEMS 187

2.1 Current electricity 187

2.2 Components of an electric circuit 188

2.2.1 Connecting wires 189

2.2.2 Battery 189

2.2.3 Switch 190

Activity 16 191

2.2.4 Resistors 191

Exercise 16 192

2.3 Effects of electrical current 194

2.3.1 Heating effect 194

Activity 17 195


Exercise 17 197

2.3.2 Magnetic effect 198

Praktiese ondersoek 13 198

2.3.2.1 Explanation 200

2.3.2.2 Applications 200

2.3.3 Chemical effect 201


Exercise 18 204



Unit 3 ELECTRICAL CIRCUITS 209

3.1 Series circuit 209



Exercise 19 213

3.2 Parallel circuit 214




3.3 Other output and input devices 220

3.3.1 Light emission diode 220

3.3.2 Photocell 220

3.3.3 Doorbell or buzzer 220

Activity 18 221

Exercise 20 222



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Unit 4 VISIBLE LIGHT 227

4.1 Light energy 227

4.2 Propagation 228

Practical investigation (demonstration) 20 228

Exercise 21 230

4.3 Radiation 230

4.4 Spectrum of visible light 231


4.5 Transparent, translucent and opaque substances 233

4.6 Absorption 233

4.6.1 Transparent coloured objects 233

4.6.2 Opaque objects 234

4.7 Reflection 235

4.7.1 Smooth surface 235

4.7.2 Rough surface 235

Exercise 22 236

4.8 Observations 236

Exercise 23 238

4.9 Refraction of light 238

4.10 Career possibilities 240

4.10.1 Optometry 240

4.10.2 Photography 240

4.10.3 Astrophysics 241

4.10.4 Careers with optic fibres 241

Exercise 24 241



Glossary 250

Term test 251

TERM 4 EARTH AND BEYOND 259

Unit 1 SOLAR SYSTEMS 259

1.1 The sun 259

1.2 Objects around the sun 260

1.2.1 Planets 260

1.2.1.1 Mercury 262

1.2.1.2 Venus 262

1.2.1.3 Earth 263

1.2.1.4 Mars 263

1.2.1.5 Jupiter 264

1.2.1.6 Saturn 264

1.2.1.7 Uranus 265

1.2.1.8 Neptune 265

Activity 19 265

1.2.2 Dwarf planets 266

1.2.3 Moons 266

1.2.4 Asteroids 267

1.2.5 Meteorites 267

1.2.6 Comets 267

Activity 20 269

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1.3 The position of earth in the universe 270

Activity 21 271

Exercise 25 272



Unit 2 BEYOND THE SOLAR SYSTEM 277

2.1 Galaxies 278

2.2 Milky Way Galaxy 278

Activity 22 279

2.3 Light years, light hours, light minutes 279

2.4 Beyond the Milky Way galaxy 280

Exercise 26 281



Unit 3 LOOKING INTO SPACE 285

3.1 Stars and different cultures 285

Activity 23 286

Activity 24 286

3.2 Telescopes 287

3.2.1 Optical telescopes 287

3.2.2 Radio telescopes 288

3.2.3 Space telescopes 288

3.2.4 SALT 288

3.2.5 SKA 289

Exercise 27 290



Glossary 296

Term test 297

Information sheet 302

Work cited 303

SAMPLE

TERM 1:LIFE AND LIVING

Doc Scientia 13NATURAL SCIENCES textbook and workbook - Grade 8

1.1 IntroductionAll living organisms require energy to survive. The interactions and interdependence between organisms in ecosystems are driven by the need for energy. This is why photosynthesis and respiration play a big role in the survival of most organisms. It is the two most important processes conducted by living organisms to obtain usable energy. The sun is one of the most important sources of energy, and supplies energy in the form of light and heat. Most plants photosynthesise, while animals must satisfy their energy needs by the process of respiration.

1.2 PhotosynthesisThe process by which plants (and some microorganisms) produce food is known as photosynthesis (photo = light; synthesis = to make).

UNIT 1 PHOTOSYNTHESIS AND RESPIRATION

Photosynthesis is the process whereby plants use carbon dioxide, water and light energy in a series of chemical reactions to produce glucose (food).

Photosynthesis MicroorganismsInteractions and interdependencies

Life and living

Photosynthesis and respiration

Photosynthesis

Respiration

Requirements of photosynthesis

Products of photosynthesis

Plants without chlorophyll

Types of respiration

Comparison between photosynthesis and respiration

Saprophytes

Parasites

SAMPLE

life and living

14 Doc Scientia NATURAL SCIENCES textbook and workbook - Grade 8

1.2.1 RequirementsWhat do plants need to photosynthesise?

Light energy

Light energy is provided by the sun.

Carbon dioxide

Plants obtain carbon dioxide (CO2) from the atmosphere.

Water

Plants obtain water from the ground.

Chlorophyll

Green plants contain the pigment chlorophyll.

Activity 1 Date:Do further research and write a short report on the requirements for photosynthesis, as well as the products that are produced during photosynthesis.

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life and living


1.2.2 Products of photosynthesisWhat do plants produce as a result of photosynthesis?

Glucose

Glucose (a simplified form of sugar) is produced by plants.

Oxygen

Oxygen (O2) is produced as a by-product, and plants release it into the atmosphere.

Photosynthesis occurs through a series of chemical reactions.The simplified chemical reaction for photosynthesis is as follows:

CO2 + H2O glucose (C6H12O6) + O2(↑) carbon dioxide water oxygen

Interesting factsChlorophyll is green because it absorbs all light from the sun, but reflects the green light.

chlorophyll

light energy

Quick factsOnly green plants contain chlorophyll. The pigment makes it possible for plants to absorb light energy and convert it to chemical energy. Chlorophyll gives plants their green colour. Not all wavelengths of energy radiated by the sun are absorbed by plants.

Quick factsThe arrow (↑) in the equation means that O2 is a gas.SAMPLE

life and living


The diagram below is a simple representation of photosynthesis:

Plants absorb carbon dioxide and release oxygen b.m.o. a process known as gaseous exchange. Gaseous exchange is the absorption and emission of gases. This happens through the stomata which are found mainly on the leaves of plants. However, stomata can also be found on other parts of the plant that are above ground, e.g. the stems. Water is absorbed from the ground through the root hairs of the plant.

Plants use glucose to respire. The energy that is released during respiration is used for the following life processes:• Propagation• Cell division• Growth• Other life processesSome glucose is converted into cellulose which forms cell walls. Excess glucose is stored as starch. Stored starch in plants serves as a food source for other living organisms.

Green plants are autotrophs. Autothropic means that plants have the ability to produce their own food.

carbon dioxide light energy

oxygen

glucose forms

water

nutrients

Quick factsStarch is insoluble in water, which is why plants store glucose in this form. SAMPLE

life and living


Plants that do not contain chlorophyll must use other ways to obtain food. Here we can distinguish between saprophytic plants and parasitic plants.

SaprophytesSaprophytes are plants that survive on dead organic tissue, e.g. sugarcane, Indian pipe and certain orchids.

Photos: Derrick Ditchburn, Victoria, CanadaParasitesParasitic plants live on living organic tissue, and obtain all its nutrients from the host. Later in the term we will study parasites in more detail. The host is harmed in the relationship.Examples of parasitic plants are dodder and mistletoe.

Practical investigation 1 Date:Aim: To prove that green plants produce starch when exposed to sunlight.

Investigative question:

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Quick factsGreen plants are the only organisms that can convert energy from the sun, into organic food. This is why plants are known as producers.

Quick factsAn investigative question always has a question mark. The answer may not be only “yes” or “no”. Tip: Start question with “How?”.SAMPLE

life and living


Hypothesis:_________________________________________________________________________________

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Apparatus:• Two living plants• A dark cupboard• Sunlight• Glass beaker• Bunsen burner• Test tube• Gauze• Glass bowl• Tripod stand• Alcohol/ethanol• Iodine solution• Water• Petri dish

Method: 1. Place the two living plants in a dark cupboard for 48 hours. 2. Take out one of the plants and expose it to sunlight for six to eight hours. 3. Pick a green leaf of the plant that has been exposed to sunlight. 4. Boil the leaf in a glass beaker filled with water. 5. Put the boiled leaf in a flask with alcohol and put the flask into a glass beaker filled with boiling

water. 6. Boil the leaf in alcohol/ethanol.7. Remove the leaf and boil it in water again.8. Spread the leaf in a Petri dish and cover it with iodine solution.9. Repeat steps 4 – 8 with one of the leaves you have picked from the plant that was left in the dark

cupboard, and compare the results.

*For absolutely accurate results, it is better to repeat this practical investigation.

water

flask

glass beaker

alcoholleaf

water

gauze

tripod stand

Quick factsHypothesis:A statement that contains the variables. It can be true or false.

SAMPLE

life and living


Questions: 1. Why do you have to boil the leaf in water first, before boiling it in alcohol/ethanol?

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2. Why do you have to heat alcohol/ethanol over water and not over an open flame?

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3. Why do you need to boil the leaf in alcohol/ethanol?

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4. What do you observe after the leaf has been boiled in alcohol/ethanol?

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5. Why do you have to boil the leaf in water the second time?

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6. What variables must remain constant during this practical investigation?

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7. What is the difference in the results between the two leaves that were tested?

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iodine solution

Petri dish

SAMPLE

Gives off Gives off

Need Need

PHOTOSYNTHESIS(green plants)

RESPIRATION(all living organisms)

SAMPLE

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6$03/(Judy McDougall - Doc · PDF fileJudy McDougall. INDEX ... Practical investigation 5 145 ... This is why photosynthesis and respiration play a big role in the survival of most