Q&A - PSLE Science

[BOOMZ]

starlight1968sg:

BOOMZ:

[quote=\"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.

Doubt this topic will be tested !
Anyway, is CFC a greenhouse gas? I thought it is a compound which reacts with ozone in the stratosphere, thus leading to the formation of an ozone hole. With this thinning of ozone layer, more UV light from the Sun can penetrates the atmosphere which thus warms up the Earth.[/quote]I'm not so sure but my Science teacher tells us that we should never be confused between global warming and Chlorofluorocarbons as they are not related.

[starlight1968sg]

May I ask if amount of frictional force depends on amount of surface area ie the bigger the surface area in contact, the larger the frictional force?

[BOOMZ]

starlight1968sg:

May I ask if amount of frictional force depends on amount of surface area ie the bigger the surface area in contact, the larger the frictional force?

Yes. The larger the surface area in contact with another surface, the greater the amount of frictional force.

[P.047330KH]

https://docs.google.com/viewer?pid=explorer&srcid=0B1RM96g5JaKuNWI0ZDM4NTUtOTE0OC00ZDJlLWFmMmEtMzVhNGQ3NzA4NjRl&chrome=true&docid=d6750013a698304303839cf29e970cc7%7Ccd046ef9be322db188d04007934d9226&a=bi&pagenumber=309&w=138

Hi,
can anyone pls help with question 6? the ans given is (2), but my DD wrote (3) . She says that a frog has many cells, like brain cells, etc, that carry out different function. :?

[Newkiasu2011]

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:

Isnt Winding of a car elastic potential energy -> KE >

[P6ians]

Dear atutor2001,

Air can be compressed,right?So why can't the volume of water be 60 ml?
TIA.

[Cockroach]

When the water level reaches 40 ml, the air in the container will resist the rest of the water and prevent more from flowing in

[Tang]

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:

Hi,

Winding up a toy car:

Chemical potential energy --> Kinetic energy --> Elastic potentital energy.

So (1) is correct.

[Tang]

bcs-dad:

Hi All,


For the question below (for question part a), the answer key is \"Oxygen\". Can some body please explain this?

My DS answer is Carbon dioxide.

http://i51.tinypic.com/x1wwat.png\">

Thanks in advance..

Hi,

The answer is given in part b - oxygen.
The aim also mentions photosynthesis, so output is oxygen.

[Tang]

bcs-dad:

Hi All,


For the question below (for question part a), the answer key is \"Oxygen\". Can some body please explain this?

My DS answer is Carbon dioxide.

http://i51.tinypic.com/x1wwat.png\">

Thanks in advance..

Hi,

The answer is given in part b - oxygen.
The aim also mentions photosynthesis, so output is oxygen.