Q&A - P3 Science

[glchua]

watmekiasu:

I did not include in the stapler because most staplers use spring pivots. I'd always assumed my magnetic one is kinda rare. It's actually so rare that I had a hard time looking for the right size bullets. :roll: The answers on MsKoh.com are sometimes arguable. It is good you brought up this question cos hopefully, a current teacher here will give us the definative answer.

Every version of thing that we bought may have a magnet somehow to enhance it's original function. However, a magnet has no actual role in a piano or a stapler. I think the answer is strictly C (telephone) and D (fridge) only.

Most microphones or speakers need magnets, fridge has a motor (compressor) so it definitely needs one.

You don't need magnets in staplers for it to function. You don't need a magnet in a piano. But both items may on and off have magnets to make it function better. I had seen a piano with a magnet before, anyone want to make a guess where it is?

Again, another very vague question. If a child had seen a magnet in a piano or a stapler, he would get this wrong.

[Tang]

glchua:

Without looking at the actual question, and judging as it is, I think the question is poorly drafted.


The potato plant uses it's roots to store food. So the primary function of that part of the plant we call \"potato\" is as a root, that is, to take in minerals and water. Storing food is a secondary function. This is the same for ginger, tapioca etc.

It is like many science questions I see in primary school, very poorly done. If a student think more, he'll get answers wrong.

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.

[tutormum]

Hi Tang,

Referring to the question in Henry Park paper.
The arrow pointed to one of the roots of the sweet potato, therefore, the correct answer is both take in water and store excess food. I think the problem is many people can't distinguish between roots and underground stem. The potato is a underground stem and so is the ginger. The stem of a plant does not take in water. Some stems like the potato and ginger store food for the plant. The carrot is another example of a root. Therefore, it is similar to the sweet potato. To tell the difference between an underground stem and a root, you have to look for root hairs on the plant part. Naturally, if it has root hairs, it is a root and not an underground stem.
Sometimes, when we become too complicated in our thinking, it may make matter worse. This is what happens in the PSLE question regarding the spraying of insecticides. Of course we can't say the student is wrong if he thinks out of the box and shouldn't discourage it. However, there is a format to follow in the teaching of science, otherwise, there will be no end in disputing every possible answers.
Hope this clarifies matter.

[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