Q&A - PSLE Science

[Newkiasu2011]

thanx


http://en.wikipedia.org/wiki/Greenhouse_gas
The above link mentions ozone as one of the gh gas. Hence confusing. I agree that ozone layer reduces the sun's heat and UV rays from reaching earth.

[Nebbermind]

atutor2001:

But option (4) specifically stated \"....but not in flask A\".

For science, this is a very strong statement and it would mean that not a tiny bit of milkiness is allowed in A.\"

I go for (1)

CO2 is a trace gas. While there may be precipitation (is that the right word?), I believe it's not enough to turn the water milky. I'll got for (4)

[ms_lim]

Please help on this question :


http://i53.tinypic.com/o54xh2.jpg\">

Ans key : (1), dd's ans : (3)

[ms_lim]

Please help on part (b) :

http://i52.tinypic.com/9kvwug.jpg\">

[Newkiasu2011]

ms_lim:

Please help on this question :


http://i53.tinypic.com/o54xh2.jpg\">

Ans key : (1), dd's ans : (3)

B is elastic potential energy

[BOOMZ]

I don’t see anything wrong with your dd’s answer….

[vlim]

ms_lim:

Please help on this question :


http://i53.tinypic.com/o54xh2.jpg\">

Ans key : (1), dd's ans : (3)

My ds also choose (3)... :roll:

[BOOMZ]

Newkiasu2011:

Does CFC cause global warming?


CFC causes ozone layer depletion. Ozone is a green house gas and causes global warming. If CFC reduces ozone, then does it mean that CFC does not affect global warming.

I read that CFC itself is a greenhouse gas. In that case, it should cause global warming.

No CFC does not cause global warming. CFC and global warming are not related. The depletion of the ozone layer causes UV rays to penetrate into Earth but does not increase the temperature. For example, Australia is near the equator, where there is a large hole in the ozone layer, but that does not necessarily mean that the temperature is affected.

I am a student taking the same exam tomorrow so do please forgive me if I am wrong in one way or another.

[BOOMZ]

ss501:

hi,

The answer given is 4, pls help to explain, thanks.
http://i51.tinypic.com/2ufaib7.jpg\">

Evaporation occurs all the time. This is not to be mixed up with boiling. Although evaporation and boiling are both gain-heat processes, evaporation takes place all the time, in all temperatures. However, boiling takes place at only 100C for pure water. Thus, the answer is (4).

Please note that I am a student taking the PSLE so please forgive me if I have made any mistakes.

[Nebbermind]

BOOMZ:

No CFC does not cause global warming. CFC and global warming are not related. The depletion of the ozone layer causes UV rays to penetrate into Earth but does not increase the temperature. For example, Australia is near the equator, where there is a large hole in the ozone layer, but that does not necessarily mean that the temperature is affected.

I am a student taking the same exam tomorrow so do please forgive me if I am wrong in one way or another.

I agree with you that in general ozone depletion is associated with UV penetrating into Earth. I took the 'energy reaching the Earth' part from some website and now I'm not sure if that would be the correct reasoning.

While I know UV will cause damage to human cells, I'm not sure what other effect it has on other lifeform, eg, plants.

Perhaps someone can share.