Q&A - P3 Science

[Tang]

elkniwt:

There's this question on an experiment. It shows a magnet attracting many nails. Then after the magnet is heated, it shows the number of nails attracted by the magnet is greatly decreased. And the qn asked : What does the experiment above show about magnets?

My dd's ans is \"If you heat a magnet, it will lose its magnetism.\" And it was marked wrong. Her teacher's ans is \"A magnet loses its magnetism when heated.\" What's the difference?? :?

The question does not seem quite correct. If when heated, the magnet has lost its magnetism, it should not have attracted any nails (and not less nails).

[tutormum]

Tang:

The question does not seem quite correct. If when heated, the magnet has lost its magnetism, it should not have attracted any nails (and not less nails).

The answer is correct. When heated, a magnet will lose its magnetism. However, the magnetic force may not be totally lost. The magnet may have become weaker and therefore is able to attract lesser nails. There is no mention of how long the magnet is heated and its strength before heating etc. This is also not the purpose of the question. Students are required in this case to understand a very basic concept, that is magnetism can be lost through heating. period.

[glchua]

Tang:

If the arrow is pointed at the sweet potato, then it is correct to state that its function is to store food.


The roots (fine roots - refer to diagram) take in water and mineral salts, not the sweet potato.

In fact a better answer is 'It is for reproduction'.

Refer to Q6 of Henry Park Prelim 2007
http://www.wendykoh.com/07/primary6-henrypark-science.pdf


Similarly for potato, ginger and tapioca, they do not take in water and mineral salts. Their functions are to store food and for reproduction.

I jumped out of bed thinking about this....I almost threw away my biology !

Logged in and saw the actual question and it confirms that I am wrong.

The function of the part pointed is mainly for storage of food. And you are right!

It is not an underground root though. Just an engorged underground stem.

I'm not so sure about the sweet potato naturally reproducing by sections of the storage organ breaking off to form a new plant. If that is the case, then the correct answer should be:

\"reproduction+storage\".

Many apologies for my previous post.

[glchua]

tutormum:

The answer is correct. When heated, a magnet will lose its magnetism. However, the magnetic force may not be totally lost. The magnet may have become weaker and therefore is able to attract lesser nails. There is no mention of how long the magnet is heated and its strength before heating etc. This is also not the purpose of the question. Students are required in this case to understand a very basic concept, that is magnetism can be lost through heating. period.

I agree. There is nothing wrong with the student's answer.

Permanent magnets depend on it's small dipoles aligned more or less towards a general direction. This is an unstable state (as in all orderly states) and the magnet will slowly lose it's magnetism over time, especially when it is a small piece (the reason why magnets should be stored sticking to one another).

Heating will accelerate this lost. Hence \"If you heat a magnet, it will lose its magnetism.\" is perfectly correct because of the word \"will\".

[Tang]

tutormum:

Tang:

The question does not seem quite correct. If when heated, the magnet has lost its magnetism, it should not have attracted any nails (and not less nails).

The answer is correct. When heated, a magnet will lose its magnetism. However, the magnetic force may not be totally lost. The magnet may have become weaker and therefore is able to attract lesser nails. There is no mention of how long the magnet is heated and its strength before heating etc. This is also not the purpose of the question. Students are required in this case to understand a very basic concept, that is magnetism can be lost through heating. period.

My dd's ans is \"If you heat a magnet, it will lose its magnetism.\" And it was marked wrong.
Her teacher's ans is \"A magnet loses its magnetism when heated.\" What's the difference??


Would it be more accurate to state that

'The magnet has become weaker.'

or

'The magnetism / magnetic force of the magnet has become weaker.'

rather than

'The magnet will lose / loses its magnetism'

which implies that the magnet is / will no longer be a magnet and will not be able to repel another magnet.

[Muffins]

elkniwt:

Hi,


Need help to clarify this marking by my dd's teacher.

There's this question on an experiment. It shows a magnet attracting many nails. Then after the magnet is heated, it shows the number of nails attracted by the magnet is greatly decreased. And the qn asked : What does the experiment above show about magnets?

My dd's ans is \"If you heat a magnet, it will lose its magnetism.\" And it was marked wrong. Her teacher's ans is \"A magnet loses its magnetism when heated.\" What's the difference?? :?

Another qn, there's a picture of sweet potato and question asks for identification of the part and function of the part. dd got right for first part. (ans is roots) but she was marked wrong for 2nd part on function. Her ans is \"It stores the food for the plant.\" Teacher's ans is \"It takes in water for the plant.\"

Hi elkniwt, your dd's first answer is absolutely right! The teacher's answer is just a rephrased version of it!

Your dd's second answer part 1 is right, but for part 2, I think that the teacher is asking for the function of THE ROOTS. Though sweet potato is a root, other fruits and veggies aren't e.g. potato (underground stem), broccoli (flower) etc. The roots do not always store food for the plant, but they ALWAYS take in water for the plant...

Hope I helped!

[PlasmaStorm]

elkniwt:

There's this question on an experiment. It shows a magnet attracting many nails. Then after the magnet is heated, it shows the number of nails attracted by the magnet is greatly decreased. And the qn asked : What does the experiment above show about magnets?

My dd's ans is \"If you heat a magnet, it will lose its magnetism.\" And it was marked wrong. Her teacher's ans is \"A magnet loses its magnetism when heated.\" What's the difference?? :?

I don't think there is any difference.

From: PlasmaStorm

[elkniwt]

Tang:

If the arrow is pointed at the sweet potato, then it is correct to state that its function is to store food.

The roots (fine roots - refer to diagram) take in water and mineral salts, not the sweet potato.

In fact a better answer is 'It is for reproduction'.

Refer to Q6 of Henry Park Prelim 2007
http://www.wendykoh.com/07/primary6-henrypark-science.pdf

Hi Tang,

The picture shown in my dd's question is exactly like the Q6 of Henry Park Prelim. It is pointed at the sweet potato not the fine roots.

[tianzhu]

Tang:

Refer to Q6 of Henry Park Prelim 2007
http://www.wendykoh.com/07/primary6-henrypark-science.pdf

Hi
Perhaps, the following links will provide useful information on the reproduction and root system of sweet potatoes. The answer given in the WS is correct.

http://www.science.edu.sg/ssc/detailed.jsp?artid=1513&type=6&root=2&parent=2&cat=18

Technical information on sweet potato plant. Please go to pg 10.
http://www.cipotato.org/library/pdfdocs/SW41119.pdf

Enjoy your reading.
Best wishes

[Tang]

PlasmaStorm:

elkniwt:

There's this question on an experiment. It shows a magnet attracting many nails. Then after the magnet is heated, it shows the number of nails attracted by the magnet is greatly decreased. And the qn asked : What does the experiment above show about magnets?

My dd's ans is \"If you heat a magnet, it will lose its magnetism.\" And it was marked wrong. Her teacher's ans is \"A magnet loses its magnetism when heated.\" What's the difference?? :?

I don't think there is any difference.

From: PlasmaStorm

Are the answers correct?

Or should we just state that 'the magnet has become weaker after heating / the magnetism or magnetic force of the magnet has been weaken by heating'? .