Q&A - PSLE Science

[atutor2001]

vidhyalog:

http://i52.tinypic.com/33vdy0j.jpg\">

Very interesting question. It is not asking for primary/food producers.

Therefore, my answer is A, B, C, D, G, H, K. All these are eaten by others. E and F are not included as they are not eaten by others and should not be considered as food sources.

[atutor2001]

Verysuperkiasu:

vidhyalog:

Need assistance for part b of this question http://i55.tinypic.com/200phn7.jpg\">

Eh....if I'm not wrong..

Frictional force is 2 objects in contact
Magnetic force is 2 objects not in contact

Atutor, can u pls verify this???

Yes, I agree with your answer. However, it is safer to use the standard key words :\"force that act at a distance\".

Magnetic force can act a distance while frictional force cannot.

[atutor2001]

vidhyalog:

Need some help with the following OE Qn http://i52.tinypic.com/2v0bcxx.jpg\">

(a) The x-axis of the graph is \"Distance from the farm\" and the graph shows decreasing number of duckweed as the distance from farm increases.

Answer : The number of duckweed at a point in the lake increases as the distance from from that point to the farm decreases. OR The number of duckweed at a point in the lake decreases as the distance from that point to the farm increases.


(b) Need logical think. Increases in the duckweed must be from something discharged by the farm - fertiliser.

Answer : Some of the fertiliser from the farm will be washed into the lake during rain which helps the duckweed to thrive (standard keyword)/ to reproduce faster.

[Alchemist]

atutor2001:

vidhyalog:

Need some help with the following OE Qn http://i52.tinypic.com/2v0bcxx.jpg\">

(a) The x-axis of the graph is \"Distance from the farm\" and the graph shows decreasing number of duckweed as the distance from farm increases.

Answer : The number of duckweed at a point in the lake increases as the distance from from that point to the farm decreases. OR The number of duckweed at a point in the lake decreases as the distance from that point to the farm increases.


(b) Need logical think. Increases in the duckweed must be from something discharged by the farm - fertiliser.

Answer : Some of the fertiliser from the farm will be washed into the lake during rain which helps the duckweed to thrive (standard keyword)/ to reproduce faster.

Thanks atutor - its a pleasure to read your answers. Wish I had discovered this earlier - but as they say - better late than never.

[Verysuperkiasu]

atutor2001:

Yes, I agree with your answer. However, it is safer to use the standard key words :\"force that act at a distance\".

Magnetic force can act a distance while frictional force cannot.

Yah now that u mentioned, think I remember coming across the phrase 'act at a distance' in the PSLE guide book under chapter on forces.

Thanks for reminding us (our chn) to use the key words, coz sometimes even if answer convey the same meaning, no keywords also minus marks.

So once again, to all parents, pls remind your chn to write down the relevant key words if they want full marks.

[Verysuperkiasu]

Which one of the following is not a source of light?


1. stars
2. firefly
3. burning torch
4. fluorescent light bulb

ans key is 4. My question : I thought all the 4 choices above are sources of light - can emit light. So why is fluorescent light bulb not a source of light?

[Cockroach]

Verysuperkiasu:

Which one of the following is not a source of light?


1. stars
2. firefly
3. burning torch
4. fluorescent light bulb

ans key is 4. My question : I thought all the 4 choices above are sources of light - can emit light. So why is fluorescent light bulb not a source of light?

I think that it is because the light bulb needs to paired with electricity to emit light, hence, i think that the answer is correct? Ha ha no confidence. The burning torch emit light as fire is present for combustion to take place.

[Cockroach]

Can someone explain to me why dry ice will be seen with white smoke when it is in contact with water?

[Verysuperkiasu]

Cockroach:

Verysuperkiasu:

Which one of the following is not a source of light?


1. stars
2. firefly
3. burning torch
4. fluorescent light bulb

ans key is 4. My question : I thought all the 4 choices above are sources of light - can emit light. So why is fluorescent light bulb not a source of light?

I think that it is because the light bulb needs to paired with electricity to emit light, hence, i think that the answer is correct? Ha ha no confidence. The burning torch emit light as fire is present for combustion to take place.

hmm....guess it makes sense. fluorescent bulb - different from the other 3 choices in that they are already lighted up. thanks!

[Cockroach]

Can someone explain to me why dry ice will be seen with white smoke when it is in contact with water?