Interactive Science (Second Edition) 2A
Workbook Solutions
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Chapter 7 LIVING THINGS AND AIR
Sectional Exercise
Section
7.1
A. Concept checking p.1
1. False
2. True
3. True
4. True
5. False
B. Multiple choice p.1-3
1. B
2. C
3. B
4. B
5. C
6. A
7. B
C. Fill in the blanks p.3
1. (a) mixture
(b) nitrogen
(c) oxygen
(d) carbon dioxide
(e) water vapour
(f) noble gases
2. relights
3. (a) red
(b) yellow
4. (a) colourless
(b) milky
5. cobalt
chloride paper
D. Matching p.4
(a) iii
(b) v
(c) i
(d) iv
(e) vi
(f) ii
E. Questions p.5-6
1. (a) A-nitrogen;
B-oxygen; C-carbon dioxide
(b) Sample Y
is breathed air, because it contains more carbon dioxide (gas C) and less oxygen (gas B).
(c) Test gas B
with a glowing splint. The glowing splint relights, showing that gas B is oxygen. (or other reasonable
answers)
2. (a) (i) carbon
dioxide
(ii) red
(iii) yellow
(iv) from colourless to milky
(b) (i) Incorrect.
It is because both hydrogencarbonate indicator and lime water cannot be used to
confirm the presence of other gases.
(ii) She should test ‘gas X’ with a glowing splint, if the glowing splint relights, the gas
is oxygen.
(c) (i) In
breathed air, the indicator changes from red to yellow.
In
unbreathed air, the indicator remains unchanged.
(ii) Breathed air contains more carbon
dioxide than unbreathed air.
Section
7.2
A. Concept checking p.7
1. True
2. True
3. False
4. False
5. False
B. Multiple choice p.7-8
1. D
2. C
3. D
4. C
5. A
6. D
C. Fill in the blanks p.9
1. (a) fuel
(b) oxygen
(c) a sufficiently high temperature
(d) fire triangle
2. (a) carbon dioxide
(b) water
(c) heat
(d) light
D. Questions p.9-10
1. B,C,F,G and
H
2. (a) (i) Fuel
Oxygen
Temperature
(ii) It shows the three necessary conditions
for burning to take place.
(b) (i) The
pan cover should be used. By covering the pan, it stops the supply of oxygen to
the burning oil.
(ii) Burning oil floats on water and spreads
the fire together with water.
Section
7.3
A. Concept checking p.11
1. True
2. False
3. True
4. False
E 5. False
B. Fill in the blanks p.11
1. (a) chemical
(b) respiration
(c) living cells
(d) oxygen
(e) carbon dioxide
(f) water
E 2. energy contents
C. Questions p.11-13
1. (a) (i) A: oxygen; B: water / carbon dioxide; C:
carbon dioxide / water
(ii) Support
body functions / support movement / maintain body temperature.
(any two or
other reasonable answers)
(b) (i) X: oxygen; Y: water / carbon dioxide; Z:
carbon dioxide / water
(ii) In both respiration and burning, oxygen is
consumed and carbon dioxide and water are produced.
(c) Respiration occurs in living cells while
burning takes place in air. /
A flame exists
in burning but not in respiration. /
Respiration is a much more
complicated process than burning. /
The energy is
released much slower in respiration than burning.
(any two or
other reasonable answer)
2. (a) Increase in temperature per gram of food
(b) 60℃
(c) The
highest water temperature reached = Water temperature at the beginning +
(change
in water temperature for 4g of
food
Z used / 2)
= 20℃ + 60℃ / 2
= 50℃
(d) Food
Z
(e)
Food Y
Overweight
/ coronary heart disease / diabetes (any two or other reasonable answers)
Section
7.4
A. Concept checking p.14
1. False
2. False
3. False
4. True
E 5. False
B. Multiple
choice p.14-16
1. A
2. D
3. D
4. B
5. D
E 6. C
E 7. A
E 8. B
C. Fill in the blanks p.17
1. (a) carbon dioxide
(b) water
(c) food
(d) oxygen
(e) starch
E 2. (a) feeding
(b) photosynthesis
(c) producers
(d) green plants
(e) consumers
D. Questions p.17-19
1. (a) A: II
B: IV
C: I
D: III
(b) C → D → B → A
(c) Dark blue
(d) This leaf has carried out photosynthesis.
E 2. (a) Chlorophyll
(b) (i) Presence
of starch in the leaf
(ii) 1. Destarch a potted plant with variegated leaves by putting
it in the dark for 1 or 2 days.
2.
Put the potted plant under bright light
for an hour.
3.
Remove a variegated leaf from the plant
and carry out the iodine test on it.
(iii)
dark blue
brown
(c) Chlorophyll is necessary for
photosynthesis.
E 3. (a)
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Producer
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Consumer (feed on plants directly)
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Consumer (feed on plants directly)
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Grass, trees (or other reasonable answers)
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rabbit, zebra, grasshopper, bird (any two)
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lion, snake (or other reasonable answer)
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(b) (i) eaten
by eaten
by
grass
zebra lion
(ii) eaten
by eaten
by
grass
rabbit snake
(or other reasonable answers)
(c) (i) Light
energy
(ii) chemical energy
(iii) chemical energy in animals
Section 7.5
A. Multiple
choice p.20-22
1. B
2. C
3. C
4. D
5. C
B. Question p.22-23
(a)
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Tube
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Does respiration take place?
(ü / û)
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Does photosynthesis take place?
(ü / û)
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Colour of the indicator
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The level of carbon dioxide (unchanged /
increase / decrease)
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A
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ü
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ü
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red
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unchanged
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B
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ü
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ü
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purple
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decrease
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C
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û
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û
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red
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unchanged
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D
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ü
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û
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yellow
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increase
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E
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ü
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û
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yellow
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increase
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F
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ü
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û
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yellow
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increase
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G
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û
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û
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red
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unchanged
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H
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ü
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û
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yellow
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increase
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(b) In the dark, the plant does not undergo
photosynthesis. However, both the plant and snail carry out respiration which
gives out carbon dioxide. Therefore, the level of carbon dioxide increases and
the indicator changes from red to yellow.
(c) Under bright light, there is a net intake of
carbon dioxide in plants. In the dark, there is a net release of carbon dioxide
in plants.
D. Questions p.36-38
1. (a) (i) oxygen
(ii) Put a glowing splint into the test tube. If
it relights, it shows that the gas is oxygen.
(iii) It is used to provide carbon dioxide for the
water plant to carry out photosynthesis.
(b) (i) The
rate of bubbling increase.
(ii) The rate of photosynthesis increases
when the light intensity increases.
2. (a) (i) It remains colourless. It shows that no
carbon dioxide is present in the air entering the bell jar.
(ii) It changes from red to yellow. It shows that
the mouse releases carbon dioxide.
(b) Sodium hydroxide solution absorbs carbon
dioxide from the incoming air. This ensures that the colour change of the
indicator in flask C is due to carbon
dioxide released from the mouse.
(c) (i) Place the set-up in the dark. (or other
reasonable answers)
(ii) Without light, the plant cannot undergo
photosynthesis. This ensures that the experimental result is due to respiration
of the plant only. (or other reasonable answer)
3. (a) (i) Respiration:
food + oxygen carbon
dioxide + water energy
(ii) light energy
Photosynthesis:
carbon dioxide +water food
+oxygen
chlorophyll
(b) (i) The
rate of net oxygen absorption will be negative.
(ii) The rate of net oxygen absorption will
be positive.
(c) (i) From
0600 to 1800
(ii) From 1800 to 2400 and 0000 to 0600
please do chapter 7.7 WB PLEASD
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