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SA1
Qn
31.
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(a)
Gravitational potential  kinetic
Link back to what we have learnt
When the distance is larger, the
hammer has more gravitational
potential energy converted to more
kinetic energy.
The hammer falls faster to hit the
metal bar deeper into the ground.
(a) and (b) share common idea
Move the toy backwards more
Note: Using the same toy
When we move the toy backwards
more, the pole will be bent more.
So, the bent pole has more elastic
potential energy converted to more
kinetic energy.
(a) and (b) share common idea ; Link back to what we have learnt
(b)
32.
(a)
(b)
Qn
33
Answers (Full marks)
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(a)
(b)
The pulling force cannot overcome
the frictional force.
We can move things on surface when our applied force can overcome
friction
She has to use more pulling force to
overcome gravity (and friction) this
time round.
She is pulling the shoe up so she also has to overcome gravity acting on
the shoe other than friction
(c)
Qn
34
Answers (Full marks)
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(a)
(Plant A / Plant B)
During photosynthesis, plant
produces oxygen which the animals
use/need (for respiration).
Link back to what we have learnt
Plant provides
shade/shelter/protection for the
animals.
(b)
Effect
The animals will die.
Reason
Muddy water blocks light reaching
plant A.
The plant cannot carry out
photosynthesis
OR
Muddy water reduces the amount of
light reaching plant A.
The plant photosynthesizes slower
The animals will have less oxygen or
not enough oxygen
(a) and (b) share common idea ; Link back to what we have learnt
Qn
35.
Answers (Full marks)
Partial Mark
(Indicate marks)
(a)
Yes.
Grass is the food producer.
When the grass is removed, all the
organisms in the food web would die
as they depend directly or indirectly
on the grass for food/energy.
(b)
(i)
Initial effect:
The snake population will increase.
Note: The eagle is removed totally
Reason: There is no predator to feed
on / prey on the snake.
(ii)
After some time:
The snake population will decrease.
Reason: When more snakes are
feeding on toads and lizards, the
populations of toads and lizards will
decrease after some time. So, the
population of snakes will also
decrease.
(c)
Organisms eat different kinds of
organisms and organisms are eaten
by different organisms.
Link back to what we have learnt
No marks
Qn
36
Partial Mark
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(a)
(b)
The water has more exposed surface
area so loses more heat to the
surroundings
Link back to what have learnt
It has small ears.
OR
It has a short/small tail.
(a) and (b) share common idea ; Link back to what we have learnt
The smaller ears reduces exposed
surface area so polar bear loses less
heat to the surroundings
(a) and (b) share common idea ; Link back to what we have learnt
Light is needed for photosynthesis
Refer to aim and results for conclusion
Carbon dioxide is needed for
photosynthesis.
Refer to aim and results for conclusion
(i)
(ii)
37
(a)
(i)
(ii)
(b)
(i)
Set-up A
Set-up B
Set-up C
dark blue
dark blue
dark blue
(a) and (b) share common idea ; Link back to what we have learnt
[1]
Qn
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(ii)
38
38
The leaves can still photosynthesize
to make food (sugar). The extra food
(sugar) will be stored as starch. This
means there will still be starch in the
leaves
(a) and (b) share common idea ; Link back to what we have learnt
Material X is a poorer heat conductor
than material Y
OR
Material Y is a better heat conductor
than material X.
OR
Material X is a poor conductor of heat
while material Y is a good conductor
of heat.
Note: Comparison must be shown
Equal to 930oC.
Melting point of a material is its physical property and does not change.
E.g. the melting point of ice is 0°C no matter how big or small the ice is.
(a)
(b)
(i)
Same material has the same melting
temperature.
(ii)
More.
The block in Set-up A is bigger so the
block has more matter, so the block
needs more heat to melt completely
Link back to what we have learnt
Qn
38
39
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(iii)
Similar trays means the same amount
of heat is conducted to the block
So, the result is due only to the size
of the block.
For a fair test, only the variable which is being tested is changed. All the
other variables are kept the same.
A fair test ensures that the results of an investigation are only due to the
variable which is changed.
One of the objects could be a magnet
while the other magnetic and both
could be attracted to each other.
Link back to what we have learnt
Note: Magnets attract magnetic materials (general statement)
Both objects must repel / move away
from each other
Link back to what we have learnt
20 cm3
Note: The drop in volume of water is due to
- Water evaporates and
- plants take in water through their roots.
Set-up B is a control set-up to show
the amount of water that evaporated
(a) and (b) share common idea ; Link back to what we have learnt
(a)
(b)
40
(a)
(b)
Qn
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(c)
41
The roots cannot not take in water
So the leaves cannot get water
OR
The roots cannot not take in water
The leaves continue to lose water in
the form of water vapour
Note:
The leaves turn brown because of drying up not because they cannot make
food
Plants take in water through their roots.
Plants use water (for photosynthesis) and lose water through their leaves in
the form of water vapour.
Organism X.
Cell A does not have a cell wall or
chloroplast, so it cannot be a plant
cell / it is an animal cell.
OR
Organism X is an animal so its cells
do not have cell wall or chloroplasts.
Note: Organism X because it has cell membrane, cytoplasm and nucleus.
(did not answer the question)
(a)
(b)
Concepts:
Note: Roots and leaves (without telling whether it is cell B or C)
Possible answers
Cell B can be found in root/flower of
plant
Cell C can be found in leaf of plant
Qn
42
Answers (Full marks)
Partial Mark
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(a)
B1 or B4.
Link back to what we have learnt
Circuit becomes open and current
cannot flow through the circuit.
(b)
Link back to what we have learnt
Can be drawn freehand
43
(a)
Make another hole at the base of the
can / side of the can.
Link back to what we have learnt
Note: The additional hole is for air to go in, not exit the can ; we have a can
of milk not a can of air
Air enters the can faster, through the
new/second hole, to take up the
space faster (previously occupied by
the milk)
OR
Air displaces milk in the can faster
(a) and (b) share common idea ; Link back to what we have learnt
(b)
Qn
44
Answers (Full marks)
(a)
(b)
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Evaporation
Link back to what we have learnt
Water vapour lost heat
to the (cooler) surrounding
air/surroundings and condensed
Note: Steam is used when water boils not evaporates
100°C
The water had already reached its
boiling point.
OR
The temperature of the water
remained constant when it was
boiling.
When the temperature of water reaches 100°C, it starts to boil.
When water is boiling, its temperature remains at 100°C.
(i)
(ii)