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Section A (28 x 2 marks)

For each of the questions from 1 to 28, four options are given. One of them is the correct answer. Make your
choice ( 1, 2, 3 or 4). Shade the correct oval (1, 2, 3 or 4) on the Optical Answer Sheet.

1. James placed two water plants and two fresh water shrimps of similar sizes into four identical tubes
as shown below. Tubes W and Y were placed in a black box each and all four tubes were placed in
the garden under sunlight for 2 hours.

All the tubes contain a carbon dioxide indicator that will change colour according to the amount
of carbon dioxide present in the water as shown below. James observed that the carbon dioxide
indicator is ink for all the tubes at the start of the experiment.

Which one of the following correctly shows the colour of the carbon dioxide indicator for each tube
after 2 hours?
2. The diagram below shows an example of how energy is transferred from one living thing to
another.

Based on the example above, which of the following statements about energy transfer are
correct?
A: The animal gets its energy directly from the sun.
B: Plants depend on the Sun as a 2rimary source of energy.
C: The transfer of energy in food chains always begins with a plant.
D: Energy from the Sun is transferred to the animal through the plant.

(1) A and C only (2) B and D only

(3) A, B and C only (4) B, C and D only

3. The diagram below shows how energy can be changed from one form to another.

Which one of the following sets of activities best represents the 3 energy changes in the
diagram?

3
 4. Escalators nowadays are installed with passenger sensors. The passenger sensor consists of a
near-distance sensor for detecting a passenger when he I she is getting on the escalator. It will
then increase its speed before he I she steps on it. The diagram below shows such an escalator.

What is the main advantage of having such an 'escalator?

(1) To conserve energy of the escalator

(2) To increase the efficiency of the escalator
(3) To allow passengers to get to the next level faster
(4) To help passengers to adjust to the speed of the escalator

5. Peter arranged a few domino blocks as shown below. He-pushed the first block and the rest of
the blocks toppled over and hit the stationary ball which moved till it stopped at position X.

Based on his observations, which of the following effects of force is I are correct? A: A force

makes a stationary object move.

B: A force makes a moving object move faster.
C: A force changes the shape and direction of a moving object.
D: A force increases the frictional for ce between the block and the ball.

(1) A only
(2) B only
(3) A and C only
(4) C and D
 6. Study the diagram below carefully. A spring was attached to the back of a meta toy car and
in front of a steel board. A wooden block was pushed against the toy car and prevented it
from moving down the ramp.

When the wooden block was removed, the toy car moved and rolled down the ramp.

Which of the following forces acted on the toy car when the wooden block was removed?

A: Frictional force
B: Magnetic force
C: Gravitational force D:
Elastic spring force

(1) A and B only

(2) C and D only
(3) A, C and D only
(4) B, C and D only

5
7. A plastic hook with a rubber part was stuck on a wall as shown below.

John hung a towel on the plastic hook. The graph below shows the amount of different types of
forces acting on the plastic hook. The friction indicated was between the rubber part and wall.

John hung one towel at a time on the plastic hook. When the third towel was hung, both the
towels and the-plastic hook fell to the ground.

Which graph correctly shows the amounts of friction between the rubber part and wall and
weight when the third towel was hung?
 8. Esther arranged two books X and Y in a way that the pages in both the books
overlap as shown in set-up 1. She pulled the books apart in opposite directions and
recorded her observations.

Pull

Book X Book Y

Set-up 1

She then changed the manner the pages overlap as seen in set-up 2 below. She repeated the
experiment and recorded her observations.

Book X Book Y

Set-up 2

Esther found that it was more difficult to pull the books apart in set-up 2.

Based on her observations recorded, which of the following conclusions made by Esther are
·correct?

A: There is more gravitational force acting on set-up 2 th an set-up 1.

B: The pages in set-up 2 had larger surface area overlapping one another.
C: The surface of the pages in set-up 1 is smoother than those in set-up
D: The friction between the surfaces of the pages in set-up 2 is more than in set-up 1.

(1) A and B only

(2) A and C only
(3) B and D only
(4) C and D only

7
 9. Four iron balls of the same mass are placed on some steps as shown in the diagram
6elow.

Which one of the following graphs correctly shows the amount of gravitational force acting
on the balls?
10. Paul set up an experiment as shown below.
String

N --- Pull

Clamp Magnet Material Spring balance

w
He pulled on the spring balance in the direction indicated until material W was separated from
the magnet. He repeated the experiment using materials X, Y and Z. The amount of force
required to separate each material from the magnet was recorded in the table below .

Paul wants to buy magnetic door stopper similar to the one shown below.

Magnet

Which material should he use for the magnetic door stopper so that the door stopper does not
detach itself easily when a strong wind blows?

(1) w
(2) X
(3) Y
(4) Z

9
11. The graph below shows the change in the area covered by plant Z in a pond over a 6-week period.
Area covered by plant Z (m2)

The table below shows the change in the number of hydrilla plants, dragonfly nymphs and tadpoles in the
same pond over the same 6-week period as a result of the change in the area covered by plant Z.

Based on the information given above, which of the following statements is I are true?

A: Plant Z is a compl etely submerged plant

B: Plan' Z prevents sunlight from reaching the hydrilla plants.
C: There was a decrease in the amount of dissolved oxygen in the pond.

(1) A only
(2) C only
(3) A and B only
(4) B and C only
12. Ruth and her friends carried out an experiment to study the preferred environment o animal X.
20 animal X were put in the mi 6dle of the box as shown below. They could move around the
box easily.

After 20 minutes, the children counted how many animal X were in each section. They did the
investigation 2 more times. They recorded their results in a table below.

Number of animal X in the different sections

A B c D
First time 1 1 5 13
Second time 2 2 5 11
Third time 2 0 4 14
Which environmental conditions did animal X prefer most?

(1) dry and bright (2) damp and dark

(3) dry and dark (4) damp and bright

13. The table below shows the characteristics of four different habitats, A, B, C and D, m an
environment.

Characteristic of Habitat
the habitat A B c D
Temperature Changes widely Changes Little or no Some changes
widely change
Light intensity High Low High Low
Presence of water Very little Very little A lot of water A lot of water

Mark found an organism in one of the habitats. He observed the following characteristics of the
organism as shown below.

The organism:
• has nee le-like leaves
• needs light for survival
• has an ability to store a lot of water

In which habitat did he most likely find the organism?

(1) A (2) B
(3) c (3) D
11
 14. Naomi wanted to find out the conditions that are most suitable for animal X to survive.
She observed the numb er of the young and adult of X she could find under different
temperatures and lighting conditions. Her results are shown in the table below.

The diagram below shows a pond and !he temperature ranges at different parts of the
pond. Animal X can be found in this pond.

30-32 °C

25-29 °C

15. Using information from Naomi 's results in the table above, at which part of the pond will
most of the young and adult of animal X be found respectively?

Study the classification table below

Which one of the following sets are suitable headings for groups A, B, C and D?
 16. The food chain below shows the interaction of animals in a field.

If all the snakes were removed , which one of the following graphs shows the most likely
effect on the populations of the other organisms?

17. The food web below shows the relationships among six organisms.

Which one of the following sets of organisms play the roles of both a prey and a predator?

(1) E and F only

(2) B, C a D only
(3) B, C and E only
(4) B, C, D and F only
13
 18. Study the following food web in a field.

The use of insecticides in the field resulted in the death of most aphids and caterpillars.

Which one of the following options correctly shows how the population size of slugs and
ladybirds are likely to be affected after the use of insecticides?

19. Four different types of pond organisms, A, B, C and D, were placed into 3 identical aquariums with
aquatic plants as shown in the table below.

The numbers of the living organisms in the aquariums were recorded every day and the following
graphs were plotted over a week. There were no dead organisms in the aquariums.

Based on the graphs above, which one of the following food chains links the four organisms correctly?
 20. David placed an iron rod between a copper rod and a steel rod, as shown in the set-up below.

Which of the following will he most likely observe when he closes the switch?
A: The bulb lights u .
B: The steel rod moves towards the iron rod .
C: The copper rod remains at the same position.
D: Both the steel and copper rods will move towards the iron rod.

(1) A and D only (2) B and C only

(3) C and D only (4) A, B and C only

21. Jacob dropped a bar magnet on the floor a few times and then measured the distance the magnet
must be brought near a nail in order to attract it.

He repeated the experiment several times and recorded the results in a table below.

Test Number of times magnet Distance between the magnet and the nail
is dropped on the floor before the nail is attracted (cm)
1 10 4
2 20 3
3 30 2.5
4 40 2

What are the variables that must be kept constant in Jacob's experiment ?
A: Type of nail
B: Type of magnet
C: Height from which the magnet is dropped
D: Number of times the magnet is dropped onto the floor

(1) A and B only (2) A and C only

(3) A, B and C only (4) B, C and D only

15
22. The set-up below shows light from a torch shining through: 3 cut-outs, R, S and P, which are
made of different material ls as shown below.

The diagram below shows the shadow that was formed on the screen.

Based on the shadow formed above, which of the following bar graphs show the amount of light
that had passed through Objects R, S and P?
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23. The diagram below shows a hot drink in a paper cup that is partially covered with cardboard.

Hot drink

Paper cup Card board with

many grooves

V':
",..

The grooves on the cardboard are useful as the air between the grooves

(l ) loses heat from the drink to the hand to keep the drink cool
(1) gains heat from the hand to the drink to keep the drink wa1m
(2) acts as a poor conductor of heat to slow down heat gain from the hand to the drink
(3) acts as a poor conductor of heat to slow down heat gain from the drink to the hand

24. A can drink at room temperature is put into a basin of water filled with ice cubes as shown in
· the diagram below.
Ice cubes Can drink

Water
Basin
The line graph below shows the changes in the temperature during the first 20 minutes.

Which lines in the graph above best represent the temperatures of the can drink can the water in
the basin respectively?

17
25. Joan had 4 pieces of metallic wrapper paper of the same size and thickness but of different type
and textures, A, B, C and D, as shown in the diagram below. She wanted to investigate if the type and
texture affect the heat absorption rate of the materials.

She left the 4 metallic wrapper papers under the hot sun for 4 hours before measuring their
temperature. She recorded the results in the table below .

Chocolates are usually wrap,ped with metallic wrapper paper to provide a barrier for light, heat,
moisture and other gases from r eacting with ·t to prevent spoilage of the chocolates too quickly.

Which one of the above pieces of metallic wrapper paper is most suitable to be used as
wrappers for the chocolates?

(1) A (2) B
(3) C (4)D
26. Study the circuit diagrams below.

A B c D
Which one of the following set-ups is matched correctly to the aim of the experiment?

27. The diagram below show the life cycle of a flowering plant.

Which of the following statements about the different stages of the Plant is I are true?
A: The plant only requires water from stage 3.
B: Fertilisation must occur at stage 4 before stage 5 can take place.
C: Light is required throughout the life cycle of the plant from stages 1 to 5 .

(l) A only
(2) B only
(3) A and C only
(4) B and C only
19
28. The diagram below shows the reproduction process in human. The fertilised egg divides to on the
different parts of the developing baby.

Which of the following statements are not correct?

A: The fertilised egg devel ops in the mother's stomach.

B: All the eggs released from the ovaries develop into you ng babi es.
C: Du ring fertilisation , only one sperm will fuse with the egg while the remaining sperms will
eventually die.
(1) A only
(2) C only
(3) A and B only
(4) A, B and C
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Section B (44 marks)
Write your answers to questions 29 to 41 in this booklet.

29. Joseph conducted an experiment on photosynthesis in a dark room using the set-up
below. The brightness of light, the amount of water, the amount of carbon dioxide in
the flask and the tracing paper were kept the same throughout the experiment. Nothing
in the set-up was moved. He measured the amount of gas collected in the syringe after
half an hour.

He repeated his experiment by increasing variable X while keeping all the other variables
constant. His results are shown below.

(a) What could be variable X be? Explain your answer clearly identifying the gas collected as
well. (2 m)

(b) Explain why Joseph Conducted his experiment in a dark room. (2 m)

(c) Joseph then decided to increase the number oi pieces of tracing papers from I to 3 pieces
to see how it would affect the results. Predict how the results would change with the number
of pieces of tracing papers used. (1 m)
30. The diagram shows how an instant water heater works.

(a) Based on the diagram above, identify the useful energy found at the various parts
in the instant water heater . (2 m)

(b) Explain what will happen to the heating of water in the pipe if more heating metal

coils are coiled round the metal pipe.

(1 m)

3
31. The diagrams below show two circuits, A and B. They show how 3 light bulbs can be connected in a house.

The owner of the house would like to cut down on the use of electricity. Which circuit, A or B,
would he choose to connect the light bulbs in the house? Explain your choice clearly. (2
m)
32. Catherine made a cat-flap to fit into a door.

Door
Pivo
t Cat-

of door
(a) When the cat has gone through the cat-flap, the flap closes on its own. Explain
clearly why the flap closes on its own using the concept on forces.
(1 m)

(b) After a while, whenever the ca goes through the cat-flap, a squeaky sound is
heard from the top part of the flap.

Explain in terms of forces, what causes the squeaky sound and. What can Catherine
do to reduce the squeaky sound?
(2 m)
(c) When a strong wind blows, the cat-flap blows open on its own. Catherine decided to
add two bar111magnets to keep the cat-flap closed so that it will not be blown open
by the wind.

On the diagram above, label both the "North" and "South" poles of the magnet on the cat-flap by
writing either "North" or "South" in the boxes provided . (1 m)

(d) After adding the two bar magnets, Catherine observes that the cat is not able to go
through the cat-flap as easily as before. Explain why the cat is not able to go through
the cat-flap as easily as before . (1 m)
33. Joshua conducted an experiment using springs P and Q of the same length. He hung a
10g load on P and Q each and measured the increase in the length of the two springs. He
repeated the experiment by adding a 10g load one at a time, until the load was 40g.

Next, Joshua started to remove a 10g load, one at a time from both P and Q, until
there was no more load left. Graph 1 and Graph 2 show his results.

(a) Based on graph 1 and 2, which spring, P or Q, can be stretched more easily?
Explain your answer clearly.(1 m)

(b)Write down the extension of Spring P when all the loads have been removed.

(c) Explain the reason for the observation stated in (b) for spring P. (1 m)
34. Te1mite mounds can be found at the base of trees . Hundreds of termites can live inside
each mound .

Termite

Fungi have also been observed to be growing inside the mounds.

(a) Explain how the fungi in the mounds can benefit the growth of trees. (l m)

Bigger and taller termite mounds can be found in a flat grassland habitat. Animal G an animal X
have been spotted standing on top of such termite mounds.

Animal G Animal X

The diagram below show a food web in this flat grassland.

(b) Based on the information provided above, give a reason how standing OIL topof
the termite mounds can enhance the survival of each of these animals. (1 m)

Animal G：
Animal X：
35. The diagram below shows part of a food web in a forest habitat.

The graph below shows a change in the numbers of animals P, Q, R and S over 2 years.

Based on the graph above, what is the most likely cause of the change in the number of R from
2016 to 2018 even though there is a decrease in the number of Q? (1 m)

How do P and S increase the population of the fruit tree T in other parts of the forest? (2 m)

9
36. Walter lowered a ring magnet onto a tray of steel ins as shown-in Diagram 1. Diagram 2 shows the
bottom view-of the magnet.

He then recorded the number of pins attracted to the bottom of the magnet at positions A, B and C
respectively. The table below shows 4 sets of reading.

(a) Which set of reading was recorded by Walter? Explain your answer clearly. (2 m)
Walter bought a magnetic drawing board as shown below.

The cross-sectional view of the magnetic drawing board is shown below.

Pen
Material Y Hole filled with
Substance X and oil

Sliding
eraser ..._

Cross sectional view of magnetic drawing board

A picture can be drawn as the tip of the pen moves across the board surface. When the
magnetic tip of the pen touches the surface, substance X moves to the top of the hole
containing oil and stays there.

To erase the picture, the sliding eraser is move across the surface below the holes. This
causes substance X to move down to its original position.

(b) How does substance X respond to the magnetic tip of the pen and the sliding eraser?
Explain your answer clearly. (2 m)
34. The set-up below uses a light sensor to count the number of people entering an elevator
as they walk in a straight line through the door.

When a person is between the light source and the sensor, his body blocks the light
from r eaching the sensor. The graph below shows the amount of light detected by
the light sensor over a period of 60 seconds.

(a) Base on the graph above, how many people enter the elevator in 1 minute? (1m)

？Give a reason for your answer？ (1m)

(b) Can the above set-up be used to count the number of children if their height is
below 80cm

？Give a reason for your answer？ (1m)

(c) Do you think the above set-up will work properly when two people walk through the
door at the same time
38. Benjamin set up an experiment to determine the amount of heat absorbed by different
surfaces. Styrofoam box A has a layer of concrete slab and styrofoam box B has a layer
of moist soil covered by grass on top of the concrete slab as shown below.

A light source was placed in each box and a data logger with temperature sensor was
connected to each box to record the temperature at the start and end of the experiment.
The set-ups were left for 1 hour and the temperature readings were recorded in the table
below.

Temperature (°C)
Box A Box B
At the start of the experiment 26.0 26.0

At the end of the experiment 29.0 27.5

(a) Based on the data in the table, the temperature of air below the concrete slab in both
boxes increase. Explain why the temperature of air in box A is higher than the air in
box B. (2 m)
Over the past five years, the Housing and Development Board (HDB) has launched HDB estates with landscaped
public rooftop gardens featured in its design as shown in the picture below.

(b) Based on Benjamin 's findings, explain why HDB flats have rooftop gardens in its
design to help i n the conservation of energy? (1 m)

(1 m)
 39. Thomas wanted to cook some potatoes using steam cookers A and B as shown
below. A steam cooker cooks food with steam and heat. He added the same
amount of water in both cookers and placed them over a heat source supplying
same amount of heat.

Lid covered with many small holes Lid with one hole

Container with
Potatoes holes at the
bottom

Support

Water
Steamer A Steamer B
(a) Thomas observed that the potatoes in steamer B were cooked faster. Explain why
the
potatoes in steamer B were cooked faster.

(b) After Thomas cooked the potatoes, he put them into a closed cardboard box
to keep them warm. He placed a piece of ridged cardboard at the bottom of box
before placing the potatoes in it as shown below.

Closed cardboard box Side view of the ridged cardboard

There are air spaces between the ridged cardboard. Explain why the ridged
cardboard is placed under the cooked potatoes to keep the potatoes warmer for
a longer period of time. (2 m)
 40. Mark used his knowledge on electrical circuit to make a game shown below.

The player must move the wand along the wire fixed to the two supports on the
box . When the ring of the wand comes into contact with the wire, bulb X lights
up and the player loses.

(a) State the property of the ring for this game to work (1 m)

(b) Complete the following diagram to show how the components are connected in the
game. The batteries are hidden in the box above.(1 m)

(c) Mark added one more bulb to the electrical circuit . When the wand made contact with
the wire, would bulb X become dimmer or brighter? Explain your answer clearl y. (1 m)

::;::>'
Mark set up another circuit as shown below. When he closed the switch, he observed that
the iron ball moved up and down between points A and B and the light bulb turned on and
off repeatedly.

(d) Explain why the light bulb turned on and off repeatedly when the switch was closed.
The diagram below shows the water level during high tide and low tide of a habitat which plant R
lives in. The adult of plant R grows in mud.

(a) The fruit of plant R hangs downwards on adult plant R. The seeds of plant R does not
fall when ripe. The seeds start to germinate in the fruit while it is on the parent plant R.
The fruits of plant R will drop during low tide after the seeds have germinated. The seeds
then continue to grow under their parent plant.

Explain why shape A is better than shape B as the geminated seed of plant R falls to the
ground under their r parent plant during the period of low tide. How will this ensure its
survival? (2 m)

(b) The germinating seeds m y not get enough sunlight under the parent plant. Will this
affect its growth? Why is that so?