Version 2
Thursday, October 15, 2009
PSLE 2009 Light OE
Q> Given a graph. The Y-axis showed the intensity of light measured by the light sensor in lux. The X-axis showed the amount of time for the parcels to travel to the end of the conveyor belt where the light source and light sensor were located.
A company wanted to know the number of parcels being scanned. So it put the parcels on the conveyor belt.
a) How many parcels were scanned?
b The company wanted to scan more parcels in the same amount of time as in (a), how could it achieve that?
Aa> Based on above information, unable to answer (a). May need to refer to actual diagram given.
Ab> The light intensity would be lower (assumed - depend on actual plot), the shorter the time the parcel reached the end of the conveyor belt, hence the faster the count. So to scan more parcels basically the company just needed to increase the speed of the conveyor belt.
To count the parcels, I would have expected the light source to be located on one side of the conveyor belt and the light sensor on the other sid. Once a parcel passed by, it would block the path of the light and the sensor would detect it and count the parcel passing at the same time.
The graph basically showed light intensity versus time for parcel to reach end of conveyor belt. So the shorter the time, the lower the light intensity (assumed - as no description of plot is given) and the faster the count and scan.
[Query - Please check if there a mistake in the X-axis - should it be distance of parcel from end of the conveyor belt rather than time for parcel to travel to end of conveyor belt]
Q> A picture of a street lamp with Daisy's shadow cast on the floor. The shadow of Daisy's head was further away from the lamp.
a) Was Daisy walking towards or away from the street lamp for her to cast a longer shadow?
b) ???
Aa> Daisy was walking away from the street lamp.
Ab>
To cast a longer shadow, the object should not be directly below the street lamp -> should be further away from the street lamp.
A company wanted to know the number of parcels being scanned. So it put the parcels on the conveyor belt.
a) How many parcels were scanned?
b The company wanted to scan more parcels in the same amount of time as in (a), how could it achieve that?
Aa> Based on above information, unable to answer (a). May need to refer to actual diagram given.
Ab> The light intensity would be lower (assumed - depend on actual plot), the shorter the time the parcel reached the end of the conveyor belt, hence the faster the count. So to scan more parcels basically the company just needed to increase the speed of the conveyor belt.
To count the parcels, I would have expected the light source to be located on one side of the conveyor belt and the light sensor on the other sid. Once a parcel passed by, it would block the path of the light and the sensor would detect it and count the parcel passing at the same time.
The graph basically showed light intensity versus time for parcel to reach end of conveyor belt. So the shorter the time, the lower the light intensity (assumed - as no description of plot is given) and the faster the count and scan.
[Query - Please check if there a mistake in the X-axis - should it be distance of parcel from end of the conveyor belt rather than time for parcel to travel to end of conveyor belt]
Q> A picture of a street lamp with Daisy's shadow cast on the floor. The shadow of Daisy's head was further away from the lamp.
a) Was Daisy walking towards or away from the street lamp for her to cast a longer shadow?
b) ???
Aa> Daisy was walking away from the street lamp.
Ab>
To cast a longer shadow, the object should not be directly below the street lamp -> should be further away from the street lamp.
Wednesday, October 14, 2009
PSLE 2009 Water
Q> Given a diagram of an inverted cup, placed on wet soil. Why the air in the cup was cooler than the surrounding air?
(1) Evaporation of water vapour from the soil (2) Condensation of water vapour (3) ? (4) ?
A> (1) Evaporation of water vapour
The water in wet soil gained heat from the soil and air in the cup and evaporated into water vapour, cooling the earth and air in the cup.
(1) Evaporation of water vapour from the soil (2) Condensation of water vapour (3) ? (4) ?
A> (1) Evaporation of water vapour
The water in wet soil gained heat from the soil and air in the cup and evaporated into water vapour, cooling the earth and air in the cup.
PSLE 2009 Reproduction of Plants
Q> Given a picture of two flowers, A and B. Someone wanted to create a fruit with characteristics of A and B. She rubbed some pollen grains from flower A onto the stigma of flower B. She then removed a part of the flower and then wrapped a plastic bag around it. What were the flower and part wrapped?
(1) Flower B and stigma (2) Flower B and anther (3) Flower A and stigma (4) Flower A and anther
A> (2) Flower B and anther
(1) Flower B and stigma (2) Flower B and anther (3) Flower A and stigma (4) Flower A and anther
A> (2) Flower B and anther
PSLE 2009 Energy OE
Q> Given a diagram of a torchlight which was on and directly below a vane.
a) Explain the energy conversion that cause the vane to spin.
[Depending on the actual question, Chemical potential energy and Electrical energy may not be necessary]
b) Explain why a brighter torchlight would cause the vane to spin faster.
Aa> Chemical potential energy (Battery) --> Electical energy (torchlight) --> Light and Heat energy --> Kinetic energy (Air) --> Kinetic energy (Vane)
Ab> With a brighter torchlight, more heat energy would be produced to heat up the air faster, causing it to rise faster and the vane to spin faster.
a) Explain the energy conversion that cause the vane to spin.
[Depending on the actual question, Chemical potential energy and Electrical energy may not be necessary]
b) Explain why a brighter torchlight would cause the vane to spin faster.
Aa> Chemical potential energy (Battery) --> Electical energy (torchlight) --> Light and Heat energy --> Kinetic energy (Air) --> Kinetic energy (Vane)
Ab> With a brighter torchlight, more heat energy would be produced to heat up the air faster, causing it to rise faster and the vane to spin faster.
Monday, October 12, 2009
PSLE 2009 Magnet
Q> Given a picture of a rod suspended freely. In the first diagram, a magnet was brought near the rod and it repelled the magnet. In the second diagram, a flame was brought near to one end of the rod. The rod was then attracted by the magnet. What caused the rod to move?
A. Gravity pulled the rod down.
B. The rod lost its magnetism
C. The flame produced kinetic energy which then pushed the rod to attract the magnet.
(1) A and B only (2) B and C only (3) A and C only (4) A, B and C
A> (1) A and B only
When the rod was heated up, it would lose its magnetism. So B is correct.
As the rod had lost its magnetism, it would not be able to repel the magnet. Hence it would be pulled down by gravity. So A is also correct.
The kinetic energy [source of flame (chemical energy) -> flame (heat energy) -> air movement (kinetic energy)] produced by the flame would unlikely be great enough to move the rod.
[With regards to the information that the rod was subsequently attracted by magnet - As the rod was made of magnetic material, it would be attracted by the magnet. The statement was redundant - it was rather there to confuse the students.]
A. Gravity pulled the rod down.
B. The rod lost its magnetism
C. The flame produced kinetic energy which then pushed the rod to attract the magnet.
(1) A and B only (2) B and C only (3) A and C only (4) A, B and C
A> (1) A and B only
When the rod was heated up, it would lose its magnetism. So B is correct.
As the rod had lost its magnetism, it would not be able to repel the magnet. Hence it would be pulled down by gravity. So A is also correct.
The kinetic energy [source of flame (chemical energy) -> flame (heat energy) -> air movement (kinetic energy)] produced by the flame would unlikely be great enough to move the rod.
[With regards to the information that the rod was subsequently attracted by magnet - As the rod was made of magnetic material, it would be attracted by the magnet. The statement was redundant - it was rather there to confuse the students.]
PSLE 2009 Adaptations OE
Q> Given a diagram showing a snake slithering and a lizard running on sand.
Give 2 reasons why the lizard can move a longer distance in the desert than the snake?
A> The snake makes more contact with the sand than the lizard, hence there is more friction to slow its movement.
As the desert sand is hot and having more contact, the snake will not be able to travel for a long time on it. The lizard can minimise contact with the sand by lift two of its limbs at a time, hence is able to travel a longer distance.
Answers not accepted
The legs of Lizard have large surface areas and will not sink into the sand easily. [Compared to the snake, the body of the snake has a even larger surface area than the legs of the lizard, isn't it?]
The lizard travels in a straight line while the snake travels in a zig-zag manner. [Question asks 'can move a longer distance' and not 'can not faster']
Give 2 reasons why the lizard can move a longer distance in the desert than the snake?
A> The snake makes more contact with the sand than the lizard, hence there is more friction to slow its movement.
As the desert sand is hot and having more contact, the snake will not be able to travel for a long time on it. The lizard can minimise contact with the sand by lift two of its limbs at a time, hence is able to travel a longer distance.
Answers not accepted
The legs of Lizard have large surface areas and will not sink into the sand easily. [Compared to the snake, the body of the snake has a even larger surface area than the legs of the lizard, isn't it?]
The lizard travels in a straight line while the snake travels in a zig-zag manner. [Question asks 'can move a longer distance' and not 'can not faster']
PSLE 2009 Electrictiy
Q> A diagram was given, showing a battery connected to a bulb, via a rod, AB. The bulb was warm but it did not light up. Which of the following is true?
(1) The bulb was faulty.
(2) The circuit was closed.
(3) The rod AB was not a conductor.
(4) The clip was made of plastic.
A> (2) The circuit was closed.
If the bulb was faulty from the start, it would unlikely to be warm.
As the bulb was warm, it meant that a current was flowing through the circuit. Hence the circuit was closed. So answer (2) is correct.
If rod AB was not a conductor, then again the bulb would not be warm.
Reasons why bulb did not light up -
Battery was weak.
As the Rod AB was in series with the bulb and had taken up a substantial voltage of the battery, leaving little left for the bulb. (Rod AB had quite a high resistance, but not to the extent to consider it as a poor conductor of electricity or insulator.)
(1) The bulb was faulty.
(2) The circuit was closed.
(3) The rod AB was not a conductor.
(4) The clip was made of plastic.
A> (2) The circuit was closed.
If the bulb was faulty from the start, it would unlikely to be warm.
As the bulb was warm, it meant that a current was flowing through the circuit. Hence the circuit was closed. So answer (2) is correct.
If rod AB was not a conductor, then again the bulb would not be warm.
Reasons why bulb did not light up -
Battery was weak.
As the Rod AB was in series with the bulb and had taken up a substantial voltage of the battery, leaving little left for the bulb. (Rod AB had quite a high resistance, but not to the extent to consider it as a poor conductor of electricity or insulator.)
PSLE 2009 Our Body Systems
Q1> Which of one the following parts of our digestive systems has the most undigested food after digestion is completed.
(1) Mouth (2) Stomach (3) Small Intestine (4) Large Intestine
A> (3) Small Intestine
Digestion is completed at the Small Intestine. So (1) Mouth and (2) Stomach are wrong.
As some of the food is digested in the Small Intestine, the amount of undigested food in the Large Intestine will unlikely be more than that found in the Small Intestine. So answer iss (3) Small Intestine.
Q7> The first diagram shows a man holding a dumbbell with his arm outstretched straight out. The second diagram shows that his arm was bent raising the dumbbell. Which of the following are required for the action?
P - Bicep / Tricep
Q - Lower Arm
R - Elbow
(1) P, Q and R (2) P and R only (3 ) ? (4) ?
A7> (1) P, Q and R
In order to lift the dumbbell, all parts of the arm, including the muscles, will be required. Hence answer is (1) P, Q and R.
(1) Mouth (2) Stomach (3) Small Intestine (4) Large Intestine
A> (3) Small Intestine
Digestion is completed at the Small Intestine. So (1) Mouth and (2) Stomach are wrong.
As some of the food is digested in the Small Intestine, the amount of undigested food in the Large Intestine will unlikely be more than that found in the Small Intestine. So answer iss (3) Small Intestine.
Q7> The first diagram shows a man holding a dumbbell with his arm outstretched straight out. The second diagram shows that his arm was bent raising the dumbbell. Which of the following are required for the action?
P - Bicep / Tricep
Q - Lower Arm
R - Elbow
(1) P, Q and R (2) P and R only (3 ) ? (4) ?
A7> (1) P, Q and R
In order to lift the dumbbell, all parts of the arm, including the muscles, will be required. Hence answer is (1) P, Q and R.
PSLE 2009 The Web of Life
Q>
The vegetables, fruit trees and butterflies form a community.
A farmer saw that catepillars were eating his vegetables, so he sprayed (lots of?) insecticides on the vegetables and fruit trees.
What would happen to the respective populations of the vegetables and fruits?
(1) Increase , Increase
(2) Decrease , Increase
(3) Increase , Decrease
(4) Decrease , Increase
A> (3) Decrease , Increase
Although (lots of?) pesticides were used and the output / yield of vegetables might not be optimal, the immediate effect would be the increase of the population of vegetables as the catepillars were killed.
With the killing of catepillars, there would be less butterflies. Regardless of the means of pollination, butterfly being one of the types of pollinators would likely to affect the production of fruits. Hence less fruits would be produced.
Whether the statement 'vegetables, fruit trees and butterflies form a community' is given or not, as this question is set at P6 level, I will expect a simple answer that the population of vegetables would increase while the number of fruit trees would decrease. Do not complicate the question by introducing other variables not given in the question.
The vegetables, fruit trees and butterflies form a community.
A farmer saw that catepillars were eating his vegetables, so he sprayed (lots of?) insecticides on the vegetables and fruit trees.
What would happen to the respective populations of the vegetables and fruits?
(1) Increase , Increase
(2) Decrease , Increase
(3) Increase , Decrease
(4) Decrease , Increase
A> (3) Decrease , Increase
Although (lots of?) pesticides were used and the output / yield of vegetables might not be optimal, the immediate effect would be the increase of the population of vegetables as the catepillars were killed.
With the killing of catepillars, there would be less butterflies. Regardless of the means of pollination, butterfly being one of the types of pollinators would likely to affect the production of fruits. Hence less fruits would be produced.
Whether the statement 'vegetables, fruit trees and butterflies form a community' is given or not, as this question is set at P6 level, I will expect a simple answer that the population of vegetables would increase while the number of fruit trees would decrease. Do not complicate the question by introducing other variables not given in the question.
PSLE 2009 Living and Non-living Things
Q2> Which of the following are needed for mould to grow on bread?
A. Oxygen
B. Light
C. Water
D. Carbon Dioxide
(1) Water only (2) Water and oxygen only (3)
A2> (2 ) Water and oxygen only.
For mould to grow on bread, the 3 conditions are water, oxygen and warmth.
Since warmth is not given, the answer will just be (2) water and oxygen only
A. Oxygen
B. Light
C. Water
D. Carbon Dioxide
(1) Water only (2) Water and oxygen only (3)
A2> (2 ) Water and oxygen only.
For mould to grow on bread, the 3 conditions are water, oxygen and warmth.
Since warmth is not given, the answer will just be (2) water and oxygen only
PSLE Heat OE
Q> Given a picture of Pots, A and B, filled with water. Each was placed on separate metal plates. For Pot B, the metal plate had a hole in the centre. The diagram also showed that 'heat' was escaping from the hole.
a) Which pot of water would boil first?
b) Explain your answer in (a).
A> a) Pot A would boil first.
b) Heat was supplied to Pot A from the metal plate. As Pot A had more contact with the metal plate, it would gain more heat than Pot B and hence boil faster.
[Assumption - Metal plate was connected to a power source / socket]
Please provide any additional information you may have about the question in the comment page.
This question is similiar to PSLE 2008 QUESTION on Cooking chestnut with sand.
Q> Given a diagram of a balance with a cup handing from each end. A lighted candle was placed near one of the cups and it tilted upwards. What caused the cup to move upwards.
(1) hot air (2) ? (3) ? (4) ?
A> hot air
When the air surrounding the lighted candle was heated up, it rose and pushed the cup upwards.
a) Which pot of water would boil first?
b) Explain your answer in (a).
A> a) Pot A would boil first.
b) Heat was supplied to Pot A from the metal plate. As Pot A had more contact with the metal plate, it would gain more heat than Pot B and hence boil faster.
[Assumption - Metal plate was connected to a power source / socket]
Please provide any additional information you may have about the question in the comment page.
This question is similiar to PSLE 2008 QUESTION on Cooking chestnut with sand.
Q> Given a diagram of a balance with a cup handing from each end. A lighted candle was placed near one of the cups and it tilted upwards. What caused the cup to move upwards.
(1) hot air (2) ? (3) ? (4) ?
A> hot air
When the air surrounding the lighted candle was heated up, it rose and pushed the cup upwards.
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