Q&A - PSLE Science

[James Ang]

CoffeeCat:

nope the presence of salt will lower the freezing point & raise the boiling point. That's why not all sea water freeze at colder areas.

The fact that water does not freeze completely at colder areas is also due to the anomalous nature of water which expands when its temperature drops to below 4 degree celsius and floats when it becomes ice and thus form a layer of ice above the water that protects the bottom layer of water from further freezing and which can still support life such as fishes. That's why people can still do fishing on frozen lakes by making a hole on the frozen ice to reach the water below the frozen surface.

[CoffeeCat]

James Ang:

The fact that water does not freeze completely at colder areas is also due to the anomalous nature of water which expands when its temperature drops to below 4 degree celsius and floats when it becomes ice and thus form a layer of ice above the water that protects the bottom layer of water from further freezing and which can still support life such as fishes. That's why people can still do fishing on frozen lakes by making a hole on the frozen ice to reach the water below the frozen surface.

i presume that the author of the book i quoted this from took this into account by meaning that not all water surface is covered by ice... i might be wrong though.

[P5G]

Please help.


http://www.orlesson.org/orp/09Sc/2009-Sc-SA1-CHS.pdf

Q21.
Which of the following does not contribute to conserving our Earth's supply of natural resources?

(1) Use energy-saving bulbs.

(2) All vehicles to use natural gas instead of petrol.

(3) Only turn on the water heater before showing.

(4) Ensure that the refrigerator is overloaded with food.


Please advise how option (2) contributes to conserving our Earth's supply of natural resources? Isn't natural gas one of the natural resources?



http://www.orlesson.org/orp/09Sc/2009-Sc-SA1-AiTong.pdf
Q14.
Which statement(s) about germination of a seed is/are correct?

A. During germination, the seed needs air, sunlight, water, food and warmth.

B. A seed does not need to make food.

C. Water is needed for germination to occur.

D. Fertiliser must be added to the seed for germination to take place.

(1) C only

(2) A and C only

(3) B and C only

(4) A, C and D only

My answer is (3) but worksheet answer is (1). Please advise which is correct.


TIA

[CoffeeCat]

P5G:

Please help.


http://www.orlesson.org/orp/09Sc/2009-Sc-SA1-CHS.pdf

Q21.
Which of the following does not contribute to conserving our Earth's supply of natural resources?

(1) Use energy-saving bulbs.

(2) All vehicles to use natural gas instead of petrol.

(3) Only turn on the water heater before showing.

(4) Ensure that the refrigerator is overloaded with food.


Please advise how option (2) contributes to conserving our Earth's supply of natural resources? Isn't natural gas one of the natural resources?



http://www.orlesson.org/orp/09Sc/2009-Sc-SA1-AiTong.pdf
Q14.
Which statement(s) about germination of a seed is/are correct?

A. During germination, the seed needs air, sunlight, water, food and warmth.

B. A seed does not need to make food.

C. Water is needed for germination to occur.

D. Fertiliser must be added to the seed for germination to take place.

(1) C only

(2) A and C only

(3) B and C only

(4) A, C and D only

My answer is (3) but worksheet answer is (1). Please advise which is correct.


TIA

For first qns, if i not wrong natural gas produce less pollution and hence \"cleaner\" than petrol. But alas natural gas is probably rarer or harder to get than the petrol way.

For 2nd, i don't think a seed need to make food because the seed itself contains food for the \"seed embryo\". The seed doesn't has any caoability to make food anyway right?

[starlight1968sg]

P5G:

Q14.

Which statement(s) about germination of a seed is/are correct?

A. During germination, the seed needs air, sunlight, water, food and warmth.

B. A seed does not need to make food.

C. Water is needed for germination to occur.

D. Fertiliser must be added to the seed for germination to take place.

(1) C only

(2) A and C only

(3) B and C only

(4) A, C and D only

My answer is (3) but worksheet answer is (1). Please advise which is correct.
TIA

My ans is also (3) bec a seed does not need to make food. It has some stored food sufficient for its growth until the leaves are developed.

[atutor2001]

P5G:

Please advise how option (2) contributes to conserving our Earth's supply of natural resources? Isn't natural gas one of the natural resources?

Hi P5G

They are probably referring to using natural gas for \"heating\" (in cold country). Compared to electricity or other forms of fuel, using natural gas for heating is the most efficient. To produce the same amount of heat energy, less natural gas is needed compared to other resources.

[tianzhu]

Hi


Seeds germinate when three conditions are met: water, correct temperature (warmth), and air(oxygen).During its early stages of growth, the seedling relies upon the food supplies stored with it in the seed until it is large enough for its own leaves to begin making food through photosynthesis.

Where does the stored food in the seeds come from?

Plants make their own food through the process of photosynthesis using light energy to make sugars from carbon dioxide and water .The food made in the leaves are transported to various parts of the plants through tubes called phloem.

Plant have different parts which perform different functions. Generally, the plant parts are roots, stems, leaves, flowers, fruits and seeds. As seeds are a part of plant, is it wrong to say that seeds make their own food? Give some thoughts.

Best wishes

[P5G]

Please help.


http://www.orlesson.org/orp/09Sc/2009-Sc-SA1-StNic.pdf


Q34c) From the experiment above, what can you conclude about the air that is breathed out and the surrounding air? [1]

Worksheet answer: Both types of air contain carbon dioxide.


My answer: The air breathed out contains more carbon dioxide than the surrounding air.


Is my answer acceptable?



Q37b) What material could object C be made of?

Worksheet answer: It could be made of magnetic materials.

My answer: Steel

Is my answer acceptable.



Question. May I know whether surrounding air will turn limewater chalky?


TIA.

[CoffeeCat]

P5G:

Please help.


http://www.orlesson.org/orp/09Sc/2009-Sc-SA1-StNic.pdf


Q34c) From the experiment above, what can you conclude about the air that is breathed out and the surrounding air? [1]

Worksheet answer: Both types of air contain carbon dioxide.


My answer: The air breathed out contains more carbon dioxide than the surrounding air.


Is my answer acceptable?



Q37b) What material could object C be made of?

Worksheet answer: It could be made of magnetic materials.

My answer: Steel

Is my answer acceptable.



Question. May I know whether surrounding air will turn limewater chalky?


TIA.

For 34c, your answer is problematic, because from where do you get the evidence to draw that comparison statement? You statement might be a fact but is unfortunately irrelevant to this question because no comparison is being made anywhere.

For 37b i think its an issue of interpreting.
Students might think that the question is asking literally for a possible answer which in your case is steel. But the teachers might be looking for the general term to cover all the possible materials, which is magnetic material in this case.

Better to learn to answer the syllabus way than risking having debatable answers, IMHO.

[underthesea]

Hi all daddies and mummies,


I need you valuable advice. My boy is taking PSLE this year. I would like to know how should I do Science revision with him? Should I go through chapter by chapter with him or just let him do as many papers as possible and learn from the mistakes he makes? I am very lost here, my boy is not very good in Science, he does not know how to apply the concept. Section A is still manageable but Section B is very bad.

Can you share you experience, TIA.