As the weight of the bird lands on P, the spring compresses. This lowers Rod R and causes X and Y to come to contact to form a closed circuit enabling electricity to pass through for the camera to take a photograph.

Contact X and Y can be moved closer to A.Use a shorter or smaller spring.Use a longer X and Y Attach a weight to Rod R

The water in the plastic tube absorbed heat from the Sun. As plastic is a poor conductor of heat it retains heat well. Hence the warm water flows upwards to the bottle and pushes the cold water out.

Understand how the model works!

Cotton wool is a poor conductor of heat. It prevents the heat from escaping into the surrounding.

The temperature of water in the plastic bottle will be higher. Metal is a better conductor of heat than plastic.OrThe temperature of water in the plastic bottle will be lower. Metal conducts heat away easily. Heat is lost as the water in the tube moves up the plastic bottle.

As the height of drop increases the depth of the dent increases. As the metal ball is held higher, gravitational potential energy of the ball increases. This in turn converts to a higher kinetic energy causing a deeper dent due to a greater impact.

Objects thrown out from high rise buildings have greater gravitational potential energy. This converts to high kinetic energy causing the object to fall at high speed with greater force.

The metal clip was made up of magnetic material. It was attracted to the magnet.

Heating has reduced the magnetism of the magnet. Hence a longer string is needed to create a closer contact between the metal clip and magnet for the magnetic force to act.

Heating reduces the strength of the magnet/ magnetism/magnetic force.

As angle x increases, a greater pulling force is needed.

Force is needed to overcome the friction between the surface of the load and plank when pulled.

The thin sheet of paper allows only some light to pass through.

When 6 sheets of paper are placed together, no light can pass through. Hence the set-up cannot count more than 6 sheets of paper.

She can place the torch nearer/Use a more powerful torch.

When the cup expanded, its volume increased but not its mass.

The candle heated up the surrounding air. As hot air rises it created a force that pushed up cup Y.

It will affect the results of the experiment. A fair test should have only 1 changed variable. The results obtained should be based on this variable.

Material Q. It can absorb most of the sound energy produced by the noisy road.

When the mixture of the metals is poured onto moving belt y, the magnetic metals from the mixture will be attracted by the magnet inside belt X. As the magnetic metals move away from the magnet the magnetic force weakens and the magnetic metals fall down due to gravity into Bin C.

Use a stronger magnet.OrIncrease the speed of belts X and Y.

Light energy Heat Energy Kinetic Energy

It would rotate faster. When a brighter light source is used it produces greater heat energy which converts to greater kinetic energy of the air.

When the light source was removed the amount of heat produced decreased causing a decrease in the kinetic energy.

No Liquid P is not a part of the circuit. Hence it does not need to be a conductor of electricity.

Yes The metal clips are connected to the container Q. Hence material Q must be conductor of electricity to complete the circuit.

5

No. It will not be in the path of light source to block the light reaching the light sensor.

Reduce the spaces between each object by placing them nearer.OrReduce the spaces between each object by placing them vertically so that more of them can be placed within the same space.

Light cannot pass through opaque objects./Light can be absorbed.

She is walking away. The length of the shadow increases as an object moves away from the light source.

The rate at which the height of shadow increased over the same period of time was greater at period Y than at period X. Hence ken concluded that Daisy walked at a slower speed during X.

PSLE Examination Questions Years 2006-2010 Science

7(a) A steel bar AB was magnetised using the stroke method as shown in Diagram 1. Diagram 2 shows the magnetic poles of AB after it was magnetised.

Another steel magnet CD was magnetised using two magnets as shown in Diagram 3.State what magnetic poles of the steel CD would be at C and D. (1)

Answer: (i) At C: South-pole(ii) At D: North-pole

PSLE Examination Questions Years 2006-2010 Science

(b) Darren wanted to magnetise a steel bar XY using the North poles of two magnets as shown in Diagram 4 below.

Give a reason why steel bar XY cannot be magnetised by Darrens method. (1)

Answer: If Darrens method is used, the steel bar will not have two distinct poles at X and Y.

PSLE Examination Questions Years 2006-2010 Science

1. Jenny filled a plastic bottle with some water. She placed the bottle near the top of a wooden plank at A as shown below. When she released the bottle, it rolled down to B.

She had other materials that she could use: Some water A stopwatch A measuring cylinder

Jenny wanted to find out how the volume of water in the bottle would affect the for time taken the bottle to roll down from A to B.

PSLE Examination Questions Years 2006-2010 Science

(a) Describe what she could carry out the experiment. (2)

(b) In her experiment, Jenny decided to keep the height of the wooden plank constant.How did this make her experiment a fair test? (1)

Answer: Jenny could fill the plastic bottle with different volumes of water. She could measure the volume of water needed by using the measuring cylinder. She could record the time taken for the plastic bottle to roll down the ramp when different amount of water is filled in the bottle.

Answer: A fair test is conducted when only one variable is changed. By maintaining the height of the wooden plank constant, she ensures that only the volume of water inside the bottles is changed.

PSLE Examination Questions Years 2006-2010 Science

7(a) William conducted an experiment by heating three similar rods made of metals A, B and C for 20 minutes. He recorded the lengths of each rod before and after the heating in the table shown.

1. Based on the results of his experiment, what could William conclude about the effect of heating different metals? (1)

Answer:Different metals increase by different lengths after heating.

PSLE Examination Questions Years 2006-2010 Science

7(a) William conducted an experiment by heating three similar rods made of metals A, B and C for 20 minutes. He recorded the lengths of each rod before and after the heating in the table shown.

(ii) In another experiment, William heated a thicker rod made of metal B of length 200mm for 20 minutes. Would the length of this rod after the heating be less than, equal to, or more than 210mm? Give a reason for your answer. (1)

Answer:1. The length of the rod will be lesser than 210mm. As the

rod is thicker it would need more heat energy to expand. Hence it would take a longer time to reach 210mm.

PSLE Examination Questions Years 2006-2010 Science

(b) A metal bridge has gaps at its ends as shown below.

What would happen to the bridge on a very hot day if there were no gaps? Give a reason for your answer. (2)Answer: If there are no gaps for expanding, the metal bridge will be bent and distorted. This is because on a very hot day, metal expands greatly and increases its length. The gaps are created to make allowance for the metal bridge to expand.

PSLE Examination Questions Years 2006-2010 Science

8. Sally filled a test tube with some water. She placed the test tube in a beaker of water. The test tube floated as shown below in Diagram 1.When she filled the test tube with more water and placed it in the beaker of water, the test tube sank as shown in Diagram 2.

(a) Give a reason why the test tube sank when it was filled with more water. (1)Answer: When water is added to the test tube, it adds on to the weight of the test tube and causes it to sink.

PSLE Examination Questions Years 2006-2010 Science

(b) A submarine is a type of boat that can travel underwater in the sea as shown in Diagram 3. It has tanks which can be filled with water. The tanks are fixed inside the submarine.

Based on Sallys experiment, what should be done to make the submarine rise from underwater to the surface of the water? (1)

Answer: The water inside the tank can be emptied to make the submarine rise to the surface of the sea.

PSLE Examination Questions Years 2006-2010 Science

9. A water tank used for flushing a toilet bowl is shown below. The flushing and re-filling system is not shown in the diagram.

After flushing, water enters and re-fills the tank. The tank will stop filling when the water reaches level L.James wanted to use less water to flush the toilet bowl. Michellesuggested putting a plastic bottle filled with stones into the water tank.1. Explain how Michelles suggestion would help reduce the amount of

water used to flush the toilet bowl. (1)The plastic bottle filled with stones will take up space inside the water tank. When water reaches level L, the water inside the water tank will become lesser.

PSLE Examination Questions Years 2006-2010 Science

9. A water tank used for flushing a toilet bowl is shown below. The flushing and re-filling system is not shown in the diagram.

After flushing, water enters and re-fills the tank. The tank will stop filling when the water reaches level L.James wanted to use less water to flush the toilet bowl. Michelle suggested putting a plastic bottle filled with stones into the water tank.(b)Michelles method is this of based on a property matter. State property. (1)

The property is matter occupies space.