Q&A - P3 Science

[mathsparks]

Lynn2:

can I check on this question?thanks


An ice cube was wrapped around with a wire mesh and placed in a test tube of water.The water around the mouth of the test tube was heated.After a few mins, it was observed that the water at the top started to boil.However, the ice cube remained frozen.

What can you conclude from this experiment?

Ans:water is a poor conductor of heat.

May I know why is it so?

My girl answer is the wire mesh is a poor conductor of heat.

Thanks again

If water is a good conductor of heat, the heat would travel from the mouth of the test tube (where it is being heated) to the bottom of the test tube, causing the ice cube to melt. However, the iced cube remained frozen, so it can be concluded that water is a poor conductor of heat.

P.S. The wire mesh is only used to make the ice cube sink, and also, it is a good conductor of heat.

Answer provided by: Mathsparks' Son(P6)

[Lynn2]

Thanks mathsparks and tianzhu for the answer…


cheers

[ChiefKiasu]

Lynn2:

Thanks mathsparks and tianzhu for the answer...


cheers

For what it's worth, some facts:
- Water has a high heat latency, ie. it can store more heat energy before its temperature rises. This is the reason for sea breeze during the day (land heats faster than the sea) and land breeze during the night (sea cools slower than land).

- The wire mesh is a GOOD conductor of heat. It conducts away the heat of the water surrounding the ice cube so that the ice does not reach melting temperature. This is the principle of the concept of \"safety lamps\" used by miners, where the open flame is surrounded by a very fine mesh of copper wire. The copper wire cools the air (potentially highly flammable methane) surrounding the flame so that it never reaches flashpoint.

[Tang]

mathsparks:

If water is a good conductor of heat, the heat would travel from the mouth of the test tube (where it is being heated) to the bottom of the test tube, causing the ice cube to melt. However, the iced cube remained frozen, so it can be concluded that water is a poor conductor of heat.


P.S. The wire mesh is only used to make the ice cube sink, and also, it is a good conductor of heat.

Answer provided by: Mathsparks' Son(P6)

Water is a poor conductor of heat. (as water does not allow heat to travel quickly from the boiling water at the top to the ice at the bottom. Wire mesh is to hold the ice down as ice will float on water.) [Words in ( ) are not required.]

[Lynn2]

Hi,can someone pls explain on this MCA found in Aitong 2008 CA2 paper. question 21


The picture shows a toy house with its shadows.

How many light source(s) is/ are there?

The answer is 2.

My girl put 1.

Thanks.

[tianzhu]

Lynn2:

The answer is 2.

My girl put 1.

Thanks.

Hi

You may wish to ask your girl why her answer is (1).

[Lynn2]

I just asked her she said cos there is only one light source to cause a shadow and image.

tianzhu:

Lynn2:

The answer is 2.

My girl put 1.

Thanks.

Hi

You may wish to ask your girl why her answer is (1).

[tianzhu]

Lynn2:

I just asked her she said cos there is only one light source to cause a shadow and image

Are you referring to the question from this link --- http://www.wendykoh.com/08/primary4-aitongca2-science.pdf

It's logical to have two sources of light in this instance.Light travels in a straight line and it's unlikely to have two shadows pointed at different directions with only one source of light.

[Lynn2]

Hi Tianzhu


Thanks for the link and explanation.

Since we are on this paper, can I also ask for question 34c,how do we conclude that for Z, we are not possible to tell.

Me and my girl are still trying to learn how to solve such question with logical thinking.Thanks alot and good day .

tianzhu:

Lynn2:

I just asked her she said cos there is only one light source to cause a shadow and image

Are you referring to the question from this link --- http://www.wendykoh.com/08/primary4-aitongca2-science.pdf

It's logical to have two sources of light in this instance.Light travels in a straight line and it's unlikely to have two shadows pointed at different directions with only one source of light.

[tianzhu]

Hi Lynn2



I guess your child is in P4.

From P4 Science, we have,

Mass is the amount of matter in a body or object.
Volume refers to the amount of space occupied by an object.

I can’t make out the volume of the middle picture with my old pair of eyes. It’s not so clear in the test paper.

Compare 1 kg of iron bar and 1 kg of cotton wool. They have the same mass, but the cotton wool has a much bigger volume.
Catch hold of a bowling ball and a basketball. Which one is bigger? Which one is heavier?

Therefore given the amount of information in this question, it’s not possible to tell the mass from the volume of water displaced.

Hope this address your concern.