Q&A - PSLE Science

[atutor2001]

Hi anneshirleygilbert


Welcome, with this site your kid doesn't need tutor. :lol:

[autolycus]

I would have to point out that the words used in the question say ‘allows light to pass through’, ‘does not allow light to pass through’, and ‘not possible to tell’.


Therefore, my answer is indeed correct, because P must allow light to pass through, whether it is made of opaque material or not. The shape of the image is irrelevant.

[atutor2001]

autolycus:

I would have to point out that the words used in the question say 'allows light to pass through', 'does not allow light to pass through', and 'not possible to tell'.


Therefore, my answer is indeed correct, because P must allow light to pass through, whether it is made of opaque material or not. The shape of the image is irrelevant.

Hi autolycus

Language wise I agree with your reasoning.

However, the question is focused on the properties of the material.
\"Which one of the following describes correctly the properties of the materials which P, Q and R are made of?\"

For example, one of the properties of metal sheet is \"it will not allow light to pass through\". If we cut a hole in the sheet, the material is still metal and the property of the material will still be \"it will not allow light to pass through\".

If the question is \"Which one of the following describes correctly the properties of the sheets P, Q and R?\", I think your argument will be valid.

Regards

[anneshirleygilbert]

Hello out there,


Need some help on 2 questions on Heat for P5.

Q1
Sarah wrapped two identical pieces of paper tightly around two rods, X and Y, separately as shown in the diagram below.

(sorry, don’t know how to show diagram)

Sarah placed each rod an equal distance over a lighted candle, ONE at a time, for 5 seconds.
She noticed that the paper on X had scorched marks on it while the paper on Y had caught fire and was burnt.
Based on Sarah’s observations, which one of the following conclusions is/are correct?
A: X is a good conductor of heat.
B: Y is a poor conductor of heat.
X is able to retain heat better than Y.
1.\tA and B only
2.\tA and C only
3.\tB and C only
4.\tA, B and C
The answer given was (1), but I think it should be (4). X, being a good conductor of heat was able to retain heat better than Y. Y is a poor conductor but caught fire from candle flame. Am I right?

Q2

A piece of metal sheet has a circular hole in the middle.

When the entire piece of metal sheet was heated evenly in an oven at high temperature for ten minutes, which one of the following describes and explains correctly what would happen?
1. Observation : The size of the hole remains the same\t
Explanation: The entire metal sheet expanded equally throughout
2. Observation : The size of the hole increases\t
Explanation: The entire metal sheet expanded equally throughout
3. Observation : The size of the hole increases\t
Explanation : Only the area around the hole expanded
4. Observation : The size of the hole decreases\t
Explanation : Only the area around the hole expanded
1.\t1
2.\t2
3.\t3
4.\t4

The answer given is (2)
But I think the observation should be the size of the hole decrease because the entire metal sheet expanded equally throughout, spreading out even to the hole, thus making the hole smaller. The expansion should not be limited to the area around the hole as the metal sheet was heated evenly in an oven. Is my reasoning right?
Unfortunately, this combination is not an option in the given answers. Pls. help.

[tianzhu]

Hi


I’ll take Q1 first.

Under the topic on heat, students learned that:

Good conductors of heat are materials that allow heat to pass through them easily.

Poor conductors of heat are materials that do not allow heat to pass through them easily.

She noticed that the paper on X had scorched marks on it while the paper on Y had caught fire and was burnt.
This is because the heat is conducted away from the paper by the rod X and the paper never gets hot enough to burn.

You may imagine rod X to be metal and rod Y to be wood.

The given answer (1) is correct.

Best wishes

[tianzhu]

Hi


For Q2, I’d go for option (2)

The size of the hole increases.

Heating the metal sheet caused it and the hole to expand and they both expanded at the same rate when the entire piece of metal sheet was heated evenly.

Best wishes

[atutor2001]

anneshirleygilbert:

Q2

A piece of metal sheet has a circular hole in the middle.

When the entire piece of metal sheet was heated evenly in an oven at high temperature for ten minutes, which one of the following describes and explains correctly what would happen?
1. Observation : The size of the hole remains the same\t
Explanation: The entire metal sheet expanded equally throughout
2. Observation : The size of the hole increases\t
Explanation: The entire metal sheet expanded equally throughout
3. Observation : The size of the hole increases\t
Explanation : Only the area around the hole expanded
4. Observation : The size of the hole decreases\t
Explanation : Only the area around the hole expanded
1.\t1
2.\t2
3.\t3
4.\t4

The answer given is (2)
But I think the observation should be the size of the hole decrease because the entire metal sheet expanded equally throughout, spreading out even to the hole, thus making the hole smaller. The expansion should not be limited to the area around the hole as the metal sheet was heated evenly in an oven. Is my reasoning right?
Unfortunately, this combination is not an option in the given answers. Pls. help.

Hi anneshirleygilbert

The circumference of the hole is actually the \"inner edge\" of the metal sheet. As the metal sheet expands equally in all directions, this \"inner edge\" must also expand i.e. become longer. That is, the circumference of the hole will become longer and therefore the hole will increase in size.

Hope it makes sense.

Regards

[anneshirleygilbert]

Thank you, Tianzhu, your explanations helped. See it now.


Thank you, atutor2001. See it now how expansion would cause the circumference to be bigger. At first, I thought the metal plate would expand towards the hole , thus making it smaller. Science can be perplexing to me, sometimes!

Thanks a lot, your prompt replies help a lot as I revise with my daughter, in preparation for the coming CA1.

[autolycus]

atutor2001: Ah, I see your point of view; I think you are absolutely right. I should have read the whole question again!

[chrisu]

May I know if Simple Machines is in the PSLE Science syllabus? Forces I checked from the MOE syllabus is included but I couldn’t find Simple Machines and yet I find some questions from assessment books regarding Simple Machines like pulley system. Thank you.