Q&A - P3 Science

[teh_oh]

atutor2001:

teh_oh:

Hi parents,

Referring to Conquer Science 3/4 Question,
Q) Study the classification table below:
Materials
Magnetic Metals - iron nail, steel screw, nickel coin
Non-magnetic Metals - aluminium foil, brass fixture, gold ring
Which of the following has been placed in the wrong category?
1) aluminium foil
2) nickel coin
3) brass fixture
4) gold ring
Answer Key: (3)

Q1) Is brass magnetic or non-magnetic metal?
Wiki state that brass is not ferromagnetic. In that case brass fixture is in the correct category above, so is the answer in the answer key above wrong?

According to EPH Ultimate Science page 473, it is stated
\"All non-metals are non-magnetic, such as plastics, paper, clay, brass, water etc\".
Q2) Is brass metal or non-metals????
Wiki state that it is a metal.

Appreciate any help.

To answer your questions first :
Q1 Brass is non-magnetic as it does not contain any magnetic element (a mixture (alloy) of copper & zinc)
Q2 Brass is a metal.

It is NOT true that all non-metals are non-magnetic. Carbon is a non-metal but it is magnetic and it also can conduct electricity.

I believe that the answer (3) is correct. The main classification should be magnetic & non-magnetic. It should then branch into \"Element\" and \"Alloy\". There are 2 alloys in the list, steel and brass. Brass must have been placed together with aluminium & gold - it should be under alloy.

If steel is placed in the same group as iron and nickel, then there is mistake in the question. Steel should be in a separate group under \"magnetic\"

Hi atutor2001,
Thanks for the information.
But can you please explain again why the answer state that 'Brass Fixture' has been placed in the wrong category if it is non-magnetic?
Thank you.

[teh_oh]

Hi parents,

For parents with children using SAP's Science Partners guide, we spotted 2 'errors' in Magnets section.

http://i53.tinypic.com/5nt9qp.jpg\">
S-pole of button magnet should be on the underside (see our arrow).

http://i52.tinypic.com/fbb4b7.jpg\">
We think it should be, \"The train and track has like poles, so magnetic repulsion occurs....\"

Please correct me if I am wrong. Thank you.

[teh_oh]

Hi parents,

Sorry to trouble again. As both my husband and I are not good in primary school syllabus, we hereby seek your assistance again.

http://i54.tinypic.com/2m29vrs.jpg\">
In the above, the iron nail becomes a temporary magnet when it comes in contact with the magnet, hence it is able to attract the paperclips.
http://i54.tinypic.com/2bob5x.jpg\">
Why didn't that surface of the iron tank that is in contact with the magnet, have temporary magnetism through 'induction' (as in the first diagram) to attract the steel ball bearing?

Thank you in advance for your assistance.

[atutor2001]

teh_oh:

Hi atutor2001,
Thanks for the information.
But can you please explain again why the answer state that 'Brass Fixture' has been placed in the wrong category if it is non-magnetic?
Thank you.

Hi teh_oh

I need to clarify on whether were the magnetic materials being printed in the question as 1 single group or were they being broken up into 2 groups, namely : iron & nickel placed together and the steel screw being placed separately, under a different column. If it is so, then (3) is correct as the main-classification is \"magnetic & non-magnetic\". The items are then sub-classified into \"Element (consist of 1 type of metal)\" and \"Alloy (mixture of metals)\".

However, if all the magnetic materials are presented in the chart as a single group (column), then there is something wrong with the question.

[teh_oh]

atutor2001:

teh_oh:

Hi atutor2001,
Thanks for the information.
But can you please explain again why the answer state that 'Brass Fixture' has been placed in the wrong category if it is non-magnetic?
Thank you.

Hi teh_oh

I need to clarify on whether were the magnetic materials being printed in the question as 1 single group or were they being broken up into 2 groups, namely : iron & nickel placed together and the steel screw being placed separately, under a different column. If it is so, then (3) is correct as the main-classification is \"magnetic & non-magnetic\". The items are then sub-classified into \"Element (consist of 1 type of metal)\" and \"Alloy (mixture of metals)\".

However, if all the magnetic materials are presented in the chart as a single group (column), then there is something wrong with the question.

Hi atutor2001,
The steel screw is placed in the same group as iron and nickel under magnetic metals. There is no mention on 'alloys' in the question. Then seems like something wrong with this question :D. Phew. Thank you.

[atutor2001]

teh_oh:

Why didn't that surface of the iron tank that is in contact with the magnet, have temporary magnetism through 'induction' (as in the first diagram) to attract the steel ball bearing?

Why nowadays no respond one?

Anyway, you are correct that the \"ENTIRE\" surface of the iron tank will become a temporary magnet due to induction. However, it has very weak magnetic force. The magnetic force from the small bar magnet is used to re-align all the \"little magnets\" in the tank (to north-south direction). With such a large tank, the magnetic force cannot completely re-align all the \"little magnets\" in the tank. Many of the \"little magnets\" in the tank are still not aligned and so the magnetic force of the tank is weak.

If we use a \"super\" strong magnet, the steel ball bearing will be stuck to the surface of the iron tank.

[Nebbermind]

children holiday, parents also holiday mah!! :imcool:

[pingathot]

Hi parents, m shocked to c the questions asked abt magnet 'cos for P4 they’ve not taught yet. U meant u parents have already get your children to do the papers in advance? Oh mine, then I must b lacking bhind.

[cimman]

pingathot:

Hi parents, m shocked to c the questions asked abt magnet 'cos for P4 they've not taught yet. U meant u parents have already get your children to do the papers in advance? Oh mine, then I must b lacking bhind.

I think different schools cover different topics for SA1. My child's school has already covered magnets for SA1 for P4.

[Niedino]

pingathot:

Hi parents, m shocked to c the questions asked abt magnet 'cos for P4 they've not taught yet. U meant u parents have already get your children to do the papers in advance? Oh mine, then I must b lacking bhind.

Hi pingathot,

Different schools will adopt a different sequence to the teaching of the Science topics. The only fixed topic is Diversity, which is taught at the beginning of P3. The rest of the topics are modular and can be taught seperately from each other. There is no prescribed sequence.

Hope it helps!