Q&A - PSLE Science

[andante]

andante:

Hi all,

I would like to find out whether the following is structural or behavioural adaptation.
- an earthworm releases mucus to help it slide through the soil quickly when it is threatened.

My DD thought that it is structural adaptation. Pls advise.

Hi,
Can someone help me on the above question ? why ?

Thank you.

[andante]

Hi,

For the question below, can someone help to explain why there will be burn mark on the leaf ? thx
http://i55.tinypic.com/20adxub.jpg\">

[Nebbermind]

atutor2001:

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??

I have to disagree with the answer given in the answer sheet.

The key word in the question is \"can be sure\". That means the option chosen must be 100% correct with no allowance for other possibility.

It is true that if the nail is being magnetised, it should be able to attract the paper clip and the magnet.

However,

Possibility 1
It is also true that if the nail is NOT magnetised, it would still be attracted to the magnet.

Possibility 2
It is also true that if the nail is NOT magnetised but if the paper clip is magnetised, the nail will be attracted to the paper clip. (unless it is stated clearly in the question that the paper clip is not magnetised)

Therefore, it is a norm that to confirm whether if an object is a magnet, we need to use repulsion.

I recently came across a similar qn for P3 like asking how to determine if a magnetic material has been magnetized. My answer to my P3 was to use the compass.

I donch think a magnetized nail will be strong enough to repel a permanent magnet.

Also, if it attracts another magnetic material, we can't be sure which is the magnetized one or both are.

So the only way to tell is to bring it towards a compass but there's no 'D only' answer.

Juz my 2c

[Herbie]

Nebbermind:

atutor2001:

[quote=\"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??

I have to disagree with the answer given in the answer sheet.

The key word in the question is \"can be sure\". That means the option chosen must be 100% correct with no allowance for other possibility.

It is true that if the nail is being magnetised, it should be able to attract the paper clip and the magnet.



However,

Possibility 1
It is also true that if the nail is NOT magnetised, it would still be attracted to the magnet.

Possibility 2
It is also true that if the nail is NOT magnetised but if the paper clip is magnetised, the nail will be attracted to the paper clip. (unless it is stated clearly in the question that the paper clip is not magnetised)

Therefore, it is a norm that to confirm whether if an object is a magnet, we need to use repulsion.

I recently came across a similar qn for P3 like asking how to determine if a magnetic material has been magnetized. My answer to my P3 was to use the compass.

I donch think a magnetized nail will be strong enough to repel a permanent magnet.

Also, if it attracts another magnetic material, we can't be sure which is the magnetized one or both are.

So the only way to tell is to bring it towards a compass but there's no 'D only' answer.

Juz my 2c [/quote]Hi Nebberminded

Yr explanation sounds logical too. Sci is so complex. I have to get my dd to ask her sci teacher liao.

Cheers

[Herbie]

Nebbermind:

atutor2001:

[quote=\"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??

I have to disagree with the answer given in the answer sheet.

The key word in the question is \"can be sure\". That means the option chosen must be 100% correct with no allowance for other possibility.

It is true that if the nail is being magnetised, it should be able to attract the paper clip and the magnet.



However,

Possibility 1
It is also true that if the nail is NOT magnetised, it would still be attracted to the magnet.

Possibility 2
It is also true that if the nail is NOT magnetised but if the paper clip is magnetised, the nail will be attracted to the paper clip. (unless it is stated clearly in the question that the paper clip is not magnetised)

Therefore, it is a norm that to confirm whether if an object is a magnet, we need to use repulsion.

I recently came across a similar qn for P3 like asking how to determine if a magnetic material has been magnetized. My answer to my P3 was to use the compass.

I donch think a magnetized nail will be strong enough to repel a permanent magnet.

Also, if it attracts another magnetic material, we can't be sure which is the magnetized one or both are.

So the only way to tell is to bring it towards a compass but there's no 'D only' answer.

Juz my 2c [/quote]Hi Nebberminded

Yr explanation sounds logical too. Sci is so complex. I have to get my dd to ask her sci teacher liao.

Cheers

[atutor2001]

[quote]
..I donch think a magnetized nail will be strong enough to repel a permanent magnet.[/quote]This is a different problem related to mass. Similarly, a small permanent magnet will not be able to move (repel) a huge permanent magnet. However, if we chose to suspend the small magnet (i.e. magnetised nail) with a string and move the big magnet towards it, the nail will move away. Although in reality it is the big magnet that repels the nail, in science term, we also conclude that the nail will repel the big magnet. Otherwise we will bring a new dimension to this type of question i.e. light magnet cannot move (repel) heavy magnet.
[quote]So the only way to tell is to bring it towards a compass but there's no 'D only' answer.[/quote]The question states that the compass moved. However, there is no clear indication that only 1 specific end of the compass needle will move towards the nail. Therefore, we cannot conclude that the movement is due to repulsion. The movement could also be due to attraction of the compass needle to a magnetic material (i.e. the nail that is still not magnetised)

[atutor2001]

andante:

andante:

Hi all,

I would like to find out whether the following is structural or behavioural adaptation.
- an earthworm releases mucus to help it slide through the soil quickly when it is threatened.

My DD thought that it is structural adaptation. Pls advise.

Hi,
Can someone help me on the above question ? why ?

Thank you.

My focus is on the word \"releases\" in the question. So my answer will be behavioural adaptation. In other words, I am making an assumption that there are other uses for the mucus.

However, if the statement is changed to \"an earthworm produces mucus which is used only to help it slide through the soil quickly when it is threatened\", I will then pick structural adaptation.

[atutor2001]

andante:

Hi,

For the question below, can someone help to explain why there will be burn mark on the leaf ? thx
http://i55.tinypic.com/20adxub.jpg\">

The glass beads are acting like magnifying glass which will converge (focus) the light rays to a point on the leaf surface. The leaf with waxy surface will not get burnt because the smooth surface can reflect the light away. On the other hand, the leaf with hairy surface will absorb the light which will be converted to heat. Accumulation of heat at a single spot caused the surface to get burnt.

[Nebbermind]

atutor2001:

This is a different problem related to mass. Similarly, a small permanent magnet will not be able to move (repel) a huge permanent magnet. However, if we chose to suspend the small magnet (i.e. magnetised nail) with a string and move the big magnet towards it, the nail will move away. Although in reality it is the big magnet that repels the nail, in science term, we also conclude that the nail will repel the big magnet. Otherwise we will bring a new dimension to this type of question i.e. light magnet cannot move (repel) heavy magnet.

I agreed with your pt.

atutor2001:

The question states that the compass moved. However, there is no clear indication that only 1 specific end of the compass needle will move towards the nail. Therefore, we cannot conclude that the movement is due to repulsion. The movement could also be due to attraction of the compass needle to a magnetic material (i.e. the nail that is still not magnetised)

Well, u can turn the nail around and see if the compass needle flip or not.

[P5G]

Please help.


http://i55.tinypic.com/20r4ltx.gif\">


TIA.