Unit 7 (2A) Worksheet

77 Living things and airLiving things and air

7.1 Gases in the air (Book 2A, p. 3)

A What is air made up of? (Book 2A, p. 3)

B Identifying gases in the air (Book 2A, p. 3)

The Earth is surrounded by a layer of air called the (1) ____________________.

Air is a mixture of gases. The table below lists the methods for identifying the gases in the air:

Gas in the air Method to identify the gas

Nitrogen No simple test as it is (2) __________________.

Oxygen It (3) __________________ a glowing splint.

Carbon dioxide It turns hydrogencarbonate indicator (4) __________________.

It turns (5) __________________ milky.

Water vapour Dry cobalt chloride paper changes from (6) _______________

to (7) _______________.

Noble gases No simple test as they are (8) __________________.

Other gases ---

Differences between the composition of unbreathed air and breathed air:

Breathed air contains (9) ______________________ (more / less) oxygen than unbreathed

air.

Breathed air contains (10) ______________________ (more / less) carbon dioxide than

unbreathed air.

The amount of water vapour in breathed air is (11) __________________ (variable /

saturated) while that in unbreathed air is (12) __________________ (variable / saturated).

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© Oxford University Press 2011 - 1 - Lesson Worksheet 2A

7.2 Air and burning (Book 2A, p. 15)

A What is burning? (Book 2A, p. 15)

Burning is a (1) __________________ reaction between a fuel and oxygen.

Oxygen supports burning. During burning, the chemical energy stored in the fuel is changed to

(2) __________________ energy and (3) __________________ energy.

The word equation of the process of burning:

B Conditions for burning (Book 2A, p. 18)

The three conditions for burning can be represented by the fire triangle.

C Putting out a fire (Book 2A, p. 19)

To put out a fire, we can remove the (9) _______________, cut off the (10) _______________

supply, and/or lower the (11) __________________ of the fire.

Carbon dioxide-type (12) ____________________________ put out a fire by releasing carbon

dioxide to displace the oxygen-containing air surrounding the object on fire.

D Preventing and surviving fire accidents (Book 2A, p. 19)

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In case of a fire accident, keep calm, act quickly and protect ourselves from (13) ___________.

7.3 How humans obtain energy (Book 2A, p. 26)

A Obtaining energy from food (Book 2A, p. 26)

Food stores (1) ________________ energy. It is the source of energy for supporting our daily

activities.

B Amounts of energy in different foods (Book 2A, p. 28)

The (2) ____________________ of food shows the amount of energy provided

by a certain quantity of the food. It is measured in (3) ________________ (kJ)

or (4) ________________ (kcal).

Taking in more energy than we need may cause health problems.

7.4 How green plants obtain energy (Book 2A, p. 31)

A Photosynthesis (Book 2A, p. 31)

Green plants can make their own food by (1) ________________________.

Complete the paragraph by referring to the diagram below:

Green plants take in (2) ________________________ and (3) __________________ from the

surroundings. The plants then build them into (4) __________________ (in the form of starch)

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Extension

using (5) __________________ energy absorbed by (6) __________________ inside the

chloroplasts in green plant cells. Oxygen is released as a (7) ____________________.

The word equation of photosynthesis:

B Test for the products of photosynthesis (Book 2A, p. 32)

We can carry out the (10) ______________________ to test for the presence of starch in green

leaves. Iodine solution changes from (11) __________________ to (12) __________________

when starch is present.

The purposes of the steps in testing for starch in a green leaf:

Step Purpose

1 Boil the leaf in water. Destroy the

(13)

_____________________ of

the cells.

2 Soak the leaf in

(14)

___________________.

Remove the chlorophyll from

the leaf.

3 Wash the leaf in hot water. Wash away the alcohol and

(15) _________________ the

leaf.

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boiling water

alcoholhot water

hot water

4 Add iodine solution to the

leaf.

Test for the presence of starch.

Hydrilla undergoes photosynthesis under light. We can test the gas

produced by the Hydrilla with a (16) _______________________.

It relights when it is put over the mouth of the bottle. This shows

that (17) __________________ is a product of photosynthesis.

C Necessary conditions for photosynthesis (Book 2A, p. 36)

We can carry out the following experiments to find out the necessary conditions for photosynthesis.

Before conducting the experiments, we have to (18) __________________ the plant by putting it in

the dark for at least 24 hours.

To show that chlorophyll is needed for photosynthesis:

Use a potted plant with (19) __________________ leaves

in the experiment.

Put the destartched plant under sunlight.

Carry out the iodine test to test for the presence of starch in the

leaf.

The (20) __________________ part of the leaf becomes blue-

black while the (21) __________________ part remains brown.

Conclusion:

(22) __________________ is needed for photosynthesis.

To show that light is needed for photosynthesis:

Wrap a part of a green leaf on a potted plant with a piece

of aluminium foil.

Put the destartched plant under sunlight.

Test for the presence of starch in the leaf. Only the part

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Extension

iodine solution

exposed to (23) __________________ turns blue-black while the part covered with the

foil remains (24) __________________.

Conclusion:

(25) __________________ is needed for photosynthesis.

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To show that carbon dioxide is needed for photosynthesis:

Set up the apparatus as shown. Soda lime absorbs

the (26) ________________________ in the air.

Put the destarched plant under sunlight.

Test for the presence of starch in both leaves.

Only leaf (27) _________ contains starch.

Conclusion:

(28) ________________________ is needed for

photosynthesis.

D Importance of photosynthesis in producing food (Book 2A, p. 41)

Green plants convert (29) _______________ energy from the sun to (30) _________________

energy stored in the food produced by photosynthesis.

The feeding relationship among living things can be represented by a (31) ________________.

Green plants are the (32) ___________________ because they make their own food. Animals

obtain food by feeding on plants or other animals. They are the

(33) ___________________.

7.5 Gaseous exchange in animals and plants

(Book 2A, p. 43)

A Respiration (Book 2A, p. 43)

Living cells use (1) __________________ to break down food and release the chemical energy

stored in them. The breaking down of food in cells produces (2) ____________________ and

(3) ____________________. This process is called (4) __________________ (呼吸作用).

The word equation of respiration:

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Extension

B Gaseous exchange in animals (Book 2A, p. 44)

1 The human respiratory system (Book 2A, p. 46)

Major parts of the human respiratory system:

The lungs are protected by the (17) __________________, which consists of the ribs, the

backbone and the chest bone.

The actions of the (18) __________________ muscles between the ribs and the

(19) __________________ brings about breathing.

2 Gaseous exchange in the air sac (Book 2A, p.47)

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Extension

Extension

In humans, gaseous exchange takes place at the surface of the (20) _________________ .

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Gaseous exchange in the air sac:

3 The breathing mechanism (Book 2A, p.48)

(a) Breathing in

1a When we breathe in, the intercostal muscles (24) __________________

and pull the ribs upwards and outwards.

1b At the same time, the diaphragm (25) ________________ and becomes

(26) __________________.

2 These movements (27) _________________ the volume of the chest cavity

and therefore

the gas pressure inside it (28) __________________.

3 When the gas pressure inside the chest cavity becomes (29)

__________________ than the atmospheric pressure, air is drawn into the

lungs.

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Extension

(21) _________________ surrounding the air sac

Oxygen passes into the capillary and is carried to body cells for carrying out (22) _________________.

The carbon dioxide produced in respiration passes into the air sac and leaves the body when we (23) ____________________.

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(b) Breathing out

1a When we breathe out, the intercostal muscles (30) __________________,

allowing the ribs to move downwards and inwards.

1b At the same time, the diaphragm (31) __________________ and returns to

its

(32) __________________ shape.

2 These movements (33) __________________ the volume of the chest

cavity and therefore the gas pressure inside it (34) __________________.

3 When the gas pressure inside the chest cavity becomes (35)

__________________ than the atmospheric pressure, air is forced out of

the lungs.

The rib cage model

Which part of the respiratory system does each part of the model represent?

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The balloon-bell jar model:

Which part of the respiratory system does each part of the model represent?

C Gaseous exchange in plants (Book 2A, p. 54)

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D The balance of oxygen and carbon dioxide in nature (Book 2A, p.58)

The diagram below shows how green plants and other living things help keep a balance of

oxygen and carbon dioxide in nature:

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Extension

Some gases in the atmosphere (e.g. carbon dioxide) can absorb (58) _____________________

from the sun and keep the Earth warm. This natural phenomenon is called the

(59) ____________________________.

Burning fossil fuels and clearing forests increase the amount of carbon dioxide in the

atmosphere. This enhances the greenhouse effect and causes (60) _______________________.

7.6 Air pollution and smoking (Book 2A, p. 62)

A Effects of polluted air on our health (Book 2A, p.62)

Burning fossil fuels gives out large amounts of (1) _________________________.

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The effects of air pollutants on health:

Air pollutant Effect on health

Sulphur dioxide,

nitrogen oxides

(2) ___________________ the eyes and throats

Irritate the lungs and causes (3) ___________________

diseases

Carbon particles Irritate the lungs

Lead particles Adversely affect the brain functions

Carbon monoxide Lowers the amount of (4) ___________________ in the blood

and causes dizziness and headaches

The (5) ______________________________________ (API) ranges from 0 to 500 and is

divided into five levels. The higher the index, the (6) ___________________ the air quality.

B Effects of smoking on our health (Book 2A, p.66)

Smoking and passive smoking largely increase the risk of developing respiratory diseases,

(7) ___________________ and (8) ___________________.

Match the harmful substances in cigarette smoke with their effects on health:

Harmful substance Effect on health

I Nicotine a Irritates the eyes, nose and skin

II Tar b Lowers the oxygen content in blood

III Carbon monoxide c Causes addiction

IV Hydrogen cyanide d Stains the teeth and finger nails

e Causes coughs and other respiratory diseases

f Increases heart rate and blood pressure

g Causes headaches and vomiting

h Causes throat and lung cancer

i Leads to heart diseases

I: (9) _______, _______ and _______ II: (10) _______, _______ and _______

III: (11) _______ IV: (12) _______ and _______

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Extension

An

sw

ers

77 Living things and airLiving things and air7.1 1 atmosphere 2 unreactive 3 relights 4 yellow

5 lime water 6 blue 7 pink 8 unreactive

9 less 10 more 11 saturated 12 variable

7.2 1 chemical 2 / 3 heat / light 4 oxygen 5 carbon dioxide

6 / 7 / 8 fuel / oxygen / high temperature 9 fuel 10 oxygen

11 temperature 12 fire extinguishers 13 smoke

7.3 1 chemical 2 energy value 3 kilojoules 4 kilocalories

7.4 1 photosynthesis 2 carbon dioxide 3 water 4 food

5 light 6 chlorophyll 7 by-product 8 carbon dioxide

9 food (starch) 10 iodine test 11 brown 12 blue-black

13 cell membranes 14 hot alcohol 15 soften 16 glowing splint

17 oxygen 18 destarch 19 variegated 20 green

21 non-green 22 Chlorophyll 23 sunlight 24 brown

25 Light 26 carbon dioxide 27 B 28 Carbon dioxide

29 light 30 chemical 31 food chain 32 producers

33 consumers

7.5 1 oxygen 2 / 3 carbon dioxide / water 4 respiration

5 oxygen 6 / 7 carbon dioxide / water 8 bronchus

9 bronchiole 10 air sac 11 intercostal muscle 12 nasal cavity

13 trachea 14 lung 15 rib 16 diaphragm

17 rib cage 18 intercostal 19 diaphragm 20 air sacs

21 capillary 22 respiration 23 breathe out 24 contract

25 contracts 26 flattened 27 increase 28 decreases

29 lower 30 relax 31 relaxes 32 dome

33 reduce 34 increases 35 higher 36 rib

37 chest bone 38 backbone 39 intercostal muscles 40 out

41 in 42 trachea 43 bronchi 44 lungs

45 diaphragm 46 in 47 out 48 higher

49 oxygen 50 carbon dioxide 51 carbon dioxide 52 carbon dioxide

53 oxygen 54 photosynthesis 55 oxygen 56 respiration

57 carbon dioxide 58 heat energy 59 greenhouse effect 60 global warming

7.6 1 air pollutants 2 Irritate 3 respiratory 4 oxygen

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5 Air Pollution Index 6 poorer 7 / 8 lung cancer / heart diseases

9 c, f, i 10 d, e, h 11 b 12 a, g

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Unit 7 (2A) Worksheet