2010 PSLE Science

[the kiasu student]

Polar bear:

Thanks.

One of my suggestions for the decomposition question was to put the jar in a dark room and my reason was that it would allow more decomposers to come into the jar, thus speeding up decomposition.

Can someone tell me if this is acceptable

You are half right and half wrong. I also said that should put it in a dark place, but not to attract decomposers nor allowing more of them go into the jar. This will reduce the rate of evaporation of the moisture from the moist leaves, hence more moisture is kept, as decomposers need water to decompose dead organisms, this would speed up decomposition.

[MOE Hater]

MOE Hater:

ApronMama:

[quote=\"Polar bear\"]anybody know the answer to the insect X question. I put 28 days but many of my friends say that it is 24 days and what is the reason for insect X staying in water for the egg larva and pupa stages

I feel that it is 24 because the question said \"after the egg hatched\" ,so it should not include the time insect x stayedin the egg stage. :lol: :lol: :lol:

Thot 28 was excluding the egg stage!!!! I put 28! :shock:[/quote]Does anyone know???!!! :idea:

[triplediao]

Kiddo98:

cocoong1998:

[quote=\"Blockbuster\"]MCQ easy, but open-ended difficult. Question on toilet bowl flushing system?!

MCQ most were easy but erm a few were quite tricky! Section B was in the middle of tough and ok ok ! the question on toilet flushing i put >the stones in the plastic bottle occupy space and the water level will reach Level L quicker. less water will be used<sth>Matter occupies space< hope this helped!

Did you say that the stones helped it to sink? I did :)[/quote]Read this is a \"Voices\" magazine they sent to my house some time ago. They didn't state the reason but it was to increase the level L in order to reduce amount/volume of water used to flush the toilet and more refilled back into the tank. At least that was my way of phrasing.
Hope this helps:)

Don't think to much about it. It's over and there is nothing you can do about it. Just go relax! Unless you have HMT like me tomorrow la, then wait 1 more day.

[triplediao]

tiggerthong1998:

Is there any other answer for the question on the boy in the jungle besides the one about transpiration? :scratchhead: :?

Many of my friends plucked a leaf,put the plastic on top and tied it with a string and when the leaf transpires,it gives out water vapour which condenses into water droplets on plastic.

Oops. I did that. Left out the string. From this moment, I despise strings. Jkjk.

[beauty queen]

is the fish questoion since it grey will blend in with the water (it lives near the surface) thus it will not be easily spotted by its predatory birds.

[triplediao]

baibai06:

anonymus:

[quote=\"tiggerthong1998\"]What did ya'll put for the magnet question in pp2 and pp1 the question where there were 3 containers ,one with a plant ,one with carbon dioxide and the last one air ?

is the ans (1)

that's what i put too....
although some of my friends put the option where the temp was
35 degree/32degree/40degree[/quote]Ans 1 isit 32/35/40?

[triplediao]

the kiasu student:

Polar bear:

anybody know the answer to the insect X question. I put 28 days but many of my friends say that it is 24 days and what is the reason for insect X staying in water for the egg larva and pupa stages

I think it is to prevent the young of insect X from being eaten by other animals.

I also mentioned about the young not having any adult to protect it from the predators as it only has a lifespan of 4 days. Oh right and the young being able to fly out of the water and onto land after it has turned into an adult. Hehe

[triplediao]

ApronMama:

Polar bear:

anybody know the answer to the insect X question. I put 28 days but many of my friends say that it is 24 days and what is the reason for insect X staying in water for the egg larva and pupa stages

I feel that it is 24 because the question said \"after the egg hatched\" ,so it should not include the time insect x stayedin the egg stage. :lol: :lol: :lol:

24days here too.

[triplediao]

thensingsmysoul:

anonymus:

[quote=\"beauty queen\"]
No i do not think so. As the rotten log habitat or the leaf litter habitat is dark i am not sure darkness is a factor for the growth of decomposers

just my 2 cents

One of the factors for Rotting log habitat is dampness n darkness. So, i think polar bear ans is correct

I said to replace a lid with one that only has 1 hole so that less water vapour can escape while still allowing the decomposers to respire. Thus the humidity in the jar increases, incresing the rate of decomposition.
Acceptable?

Based on my mini 'research', darkness is not a factor that contributes to speeding up decomposition.

The answer is dependent on how the question is asked, but basically, the rate of decomposition is dependent upon:
* Temperature (the warmer the better);
* The availability of oxygen;
* Access by scavengers;
* Humidity, or wetness;
* Rainfall/Dampness;
etc...

:)[/quote]I said to replace a lid with one that only has 1 hole so that less water vapour can escape while still allowing the decomposers to respire. Thus the humidity in the jar increases, incresing the rate of decomposition.
Acceptable?

[sam6312]

the kiasu student:

One of the questions from today's paper was like this:


A 200cm metal rod was heated for 20mins and expanded to a length of 210cm. John took another 200cm metal rod, made of the same type of metal, but thicker. He heated it for 20mins. Will the length of the thicker rod be shorter or longer than 210cm or be the same? Explain.

My answer: Longer. The amount of matter in the thicker rod was more than the amount of matter in the first rod, hence the thicker rod would expand to more than 210cm. :? :? :? :? :? :? :? :? :? :? :?

It should be shorter what???