2010 PSLE Science

[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???

[sam6312]

MOE Hater:

MOE Hater:

[quote=\"ApronMama\"]
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:

Does anyone know???!!! :idea:[/quote]

[ZoeyTan]

i think my answers are totally wrong…

could u all see whether it is acceptable?

My answer: he should water the plant daily as with more moisture,decomposition can take place faster.

he could increase the number of holes at the lid so that more oxygen could enter the bin. with more oxygen, the rate of decomposition will be higher.

(i felt that it is totally wrong)…

another thing…about the forest one…what he is thirsty then the plants and fruits could nt be eaten that one… i wrote he could cover the leaves of the plant with the plastic sheet using the string.As the plant repire, it gives off water vapour through its stomato. As the water vapour condenses onto the cooler inner surface of the plastic sheet, it will become water droplets. The boy can drink the water droplets…

and another thing …about the toilet…
i wrote as the plastic bottle occupy space, it will take up some space in the tank, therefore, lesser water is needed to fill up the tank

b) Solid occupies space…(it is wrong?i should write matter right?)

[mum-in-action]

It should be 10... Read carefully, the graph said that how long did each stage lasted or smth like dat. I am veri confident that it is 10, cus the pupa stage + larva stage for it to reach adult stage. Hence, it is 4+6[/quote]


nono. the stages on the graph are put wrongly. it goes like this. egg, adult, larva, pupa. the pupa has 6 stages. egg has 4 stages like the adult. larva has 18 stages. so 18+6=24

[sam6312]

ZoeyTan:

i think my answers are totally wrong....

could u all see whether it is acceptable?

My answer: he should water the plant daily as with more moisture,decomposition can take place faster.

he could increase the number of holes at the lid so that more oxygen could enter the bin. with more oxygen, the rate of decomposition will be higher.

(i felt that it is totally wrong)....

another thing...about the forest one..what he is thirsty then the plants and fruits could nt be eaten that one... i wrote he could cover the leaves of the plant with the plastic sheet using the string.As the plant repire, it gives off water vapour through its stomato. As the water vapour condenses onto the cooler inner surface of the plastic sheet, it will become water droplets. The boy can drink the water droplets..

and another thing ...about the toilet...
i wrote as the plastic bottle occupy space, it will take up some space in the tank, therefore, lesser water is needed to fill up the tank

b) Solid occupies space..(it is wrong?i should write matter right?)

Dun be too depress, cheerup. But I am sorry to say that yeah it shud be matter occupies space and he shud not water the dead leaves. But guess wat? ur leaves question is correct!

[ZoeyTan]

sam6312:

ZoeyTan:

i think my answers are totally wrong....

could u all see whether it is acceptable?

My answer: he should water the plant daily as with more moisture,decomposition can take place faster.

he could increase the number of holes at the lid so that more oxygen could enter the bin. with more oxygen, the rate of decomposition will be higher.

(i felt that it is totally wrong)....

another thing...about the forest one..what he is thirsty then the plants and fruits could nt be eaten that one... i wrote he could cover the leaves of the plant with the plastic sheet using the string.As the plant repire, it gives off water vapour through its stomato. As the water vapour condenses onto the cooler inner surface of the plastic sheet, it will become water droplets. The boy can drink the water droplets..

and another thing ...about the toilet...
i wrote as the plastic bottle occupy space, it will take up some space in the tank, therefore, lesser water is needed to fill up the tank

b) Solid occupies space..(it is wrong?i should write matter right?)

Dun be too depress, cheerup. But I am sorry to say that yeah it shud be matter occupies space and he shud not water the dead leaves. But guess wat? ur leaves question is correct!

then how about the oxygen one? and the toilet a)?

[sam6312]

ZoeyTan:

sam6312:

[quote=\"ZoeyTan\"]i think my answers are totally wrong....

could u all see whether it is acceptable?

My answer: he should water the plant daily as with more moisture,decomposition can take place faster.

he could increase the number of holes at the lid so that more oxygen could enter the bin. with more oxygen, the rate of decomposition will be higher.

(i felt that it is totally wrong)....

another thing...about the forest one..what he is thirsty then the plants and fruits could nt be eaten that one... i wrote he could cover the leaves of the plant with the plastic sheet using the string.As the plant repire, it gives off water vapour through its stomato. As the water vapour condenses onto the cooler inner surface of the plastic sheet, it will become water droplets. The boy can drink the water droplets..

and another thing ...about the toilet...
i wrote as the plastic bottle occupy space, it will take up some space in the tank, therefore, lesser water is needed to fill up the tank

b) Solid occupies space..(it is wrong?i should write matter right?)

Dun be too depress, cheerup. But I am sorry to say that yeah it shud be matter occupies space and he shud not water the dead leaves. But guess wat? ur leaves question is correct!

then how about the oxygen one? and the toilet a)?[/quote]U didnt say that the stones make the plastic bottle heavier... Cus if u put plastic bottle the water will just float on the surface. Then, the oxygen wan... maybe can. There are alternatives to answers in PSLE espacially science, so dun worry go on and celebrate if u do not hav HCL 2morrow. Sad to say, I do.