Q&A - PSLE Science

[atutor2001]

P5G:

Please help.


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TIA.

(a) She waited for 2 minutes to allow time for heat to travel from the water bath to the water in the test tube so that the temperature of every part of the water in the test tube has reached 20 degree C.

(b) Conducting the experiment in a cool room will improve the accuracy because temperature of the water in the test tube will be quite the same as the temperature in a cool room and this will minimise heat gained or loss by the experiment set-up.

(c) The physical factor needed is warmth

[atutor2001]

Publica:

Hi,


I have a question regarding melting. We know that the temperature of the melting ice will remain at 0 Deg C until the ice has melted completely. However, will the temperature of the water from the melting ice increase as the ice is still melting as it gains heat from the surrounding air?

Thanks.

If the water is still in contact with the ice, the normal answer is NO (for science question) because it is assumed that any gain in heat by the water will flow to the ice and will be used to cause more of the ice to melt.

However, if the water has flown to quite a distance from the ice, it will take time for the heat gain to travel to the ice. Therefore, in reality, melted water that has flown to quite a distance from the ice can actually be more than 0 degree if the environment is very hot.

[Publica]

atutor2001:

Publica:

Hi,


I have a question regarding melting. We know that the temperature of the melting ice will remain at 0 Deg C until the ice has melted completely. However, will the temperature of the water from the melting ice increase as the ice is still melting as it gains heat from the surrounding air?

Thanks.

If the water is still in contact with the ice, the normal answer is NO (for science question) because it is assumed that any gain in heat by the water will flow to the ice and will be used to cause more of the ice to melt.

However, if the water has flown to quite a distance from the ice, it will take time for the heat gain to travel to the ice. Therefore, in reality, melted water that has flown to quite a distance from the ice can actually be more than 0 degree if the environment is very hot.

Hi atutor2001,
Thanks for the prompt reply. That was what my son understood to be but the answer key gave a different answer.

[atutor2001]

Publica:

atutor2001:

[quote=\"Publica\"]Hi,


I have a question regarding melting. We know that the temperature of the melting ice will remain at 0 Deg C until the ice has melted completely. However, will the temperature of the water from the melting ice increase as the ice is still melting as it gains heat from the surrounding air?

Thanks.

If the water is still in contact with the ice, the normal answer is NO (for science question) because it is assumed that any gain in heat by the water will flow to the ice and will be used to cause more of the ice to melt.

However, if the water has flown to quite a distance from the ice, it will take time for the heat gain to travel to the ice. Therefore, in reality, melted water that has flown to quite a distance from the ice can actually be more than 0 degree if the environment is very hot.

Hi atutor2001,
Thanks for the prompt reply. That was what my son understood to be but the answer key gave a different answer.[/quote]In the past, the standard answer for such type of question is that the temperature of water from melted ice is always 0 degree as long as the ice has not completely melted. Not sure is the answer key still following this norm. If Yes, then the I suggest to \"just follow it\" unless there is emphasis in the question that the water has flown to quite a distance from the ice.

[atutor2001]

P5G:

Please help.


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TIA.

My interpretation of the graph is that Line 1 is for Transpiration and Line 2 is Photosynthesis.

(a) The rat will die and the plant will continue to survive.

(b) The rat died because it has no food. The plant can survive because it can continue to make its own food.

Personally, I think it is ok to say that both rat and plant will survive because rat can survive for 1 week without food. However, I have chosen to answer that rat will die because my guess is that the question is testing on \"difference in ability to make its own food between plant and animal\"

[atutor2001]

P5G:

Please help.


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TIA.

(a) The rate of photosynthesis of water plants without the presence of light (in darkness) is faster at higher temperature.
OR
The rate of photosynthesis of water plants without the presence of light (in darkness) is slower at higher temperature.
....

(b) All the water plants will die because there is no light for it to carry out photosynthesis to make food.

[atutor2001]

P5G:

Please help.


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TIA.

(i) Ostrich should be placed in Group C

(ii) The organisms are grouped by the type of food they eat. Group A are carnivores, B are Herbivores and C are Omnivores

[Herbie]

i hv a qn.


Raju wante to find whether a nail was magnetised. He put it near a magnet, a compass and a paper clip. He recorded his observations below

A. It repelled the magnet.
B. It attracted the magnet.
C. It attracted the paper clip.
D. It could move the compass needle.

From which of the above observations can be sure that the nail waagnetised?

1. A only
2. A and C only
3. B and C only
4. A, B, C and D

[atutor2001]

Herbie:

i hv a qn.


Raju wante to find whether a nail was magnetised. He put it near a magnet, a compass and a paper clip. He recorded his observations below

A. It repelled the magnet.
B. It attracted the magnet.
C. It attracted the paper clip.
D. It could move the compass needle.

From which of the above observations can be sure that the nail waagnetised?

1. A only
2. A and C only
3. B and C only
4. A, B, C and D

Answer is (1) A only because magnet can only be confirmed by repulsion. Attraction can happen between a magnet and a magnetic material.

[Herbie]

hi atutor,

The answer on the answer sheet is 3.

If the nail is being magetised, it shld also be able to attract the paper clip and attract the magnet too right??