Q&A - PSLE Science

[atutor2001]

htn:

need help, Rosyth preliminary 2010


Q22. A block of ice is put in a sealed plastic box.The box is then placed in the middle of a classroomon a hot day.

What will happen to the temperature of the melting ice, the water and the air in the box after some time?


Temperature of

melting ice water air in the box

1.remains the same increases decreases
2.decreases remains the same increases
3.remains the same decreases decreases
4.increases remains the same increases

what is the ans?

TIA

I will pick (1)
However, if the ice and water is in a small container (e.g. glass), then the temperature of the water will remain at 0 degree C.

[atutor2001]

P5G:

Please help.


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TIA.

A and G are important because they are the food producer which all other organisms in the community depends on either directly or indirectly for food and energy.

B obtains energy directly from the producer A & G but D obtains energy directly only from G. Energy from A is transferred to D indirectly through F & E and some energy is lost along the way. Therefore, the total amount of energy of organisms B will be more than the total amount of energy of organisms D. This implies that the number of organism B will be more than D. Therefore, C will consume more organism B than D.
(this is correct only if the physical size of each B and D are about the same - technically this question is wrong)

[P5G]

Please help.


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TIA.

[P5G]

Please help.


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TIA.

[atutor2001]

P5G:

Please help.


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TIA.

a) green lace wing flies because they help to get rid of aphids

b) For sudden drop in population size, remember the following causes :

(i) drought / famine
(ii) disease
(iii) introduction of predators
(iv) migration (seasonal)
(v) change from larva to pupa etc.

Use them in the order above.

[atutor2001]

P5G:

Please help.


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TIA.

The spirometer measures volume of air that enters and leaves the lungs.

Graph is showing volume of air on the y-axis.

Although it is not stated on the axis we can quite safely interpret that the graph is showing the volume of air inside the lungs because it never reaches zero (if volume of air is zero, the lungs collapsed which causes death).

Therefore, B is exhaling as the volume of air in the lungs decreases.

[ms_lim]

Hi, can you help to explain this question? Ans key is 1 but my dd's ans is 4 :

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[hashroop]

Good Morning


Not sure if someone has posted this before…

Pei Chun Public Sch 2011 Prelim
Q23 is based on Simple Machines!
Strange as this topic has been dropped from the syllabus 1 year ago!

[ms_lim]

Please help to explain this qn :

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Ans key for :
bi) It would move towards the flask with black surface.
ii) Black surface absorbs heat faster, thus causing the mouth of the flask to expand faster. The coloured ink will then move towards the expanded part of the tube.
My dd's answer :
bi) It would move towards the flask with white surface.
ii) Black surface absorbs heat faster, so the gas inside the black surface flask will gain heat faster and expand. As gas expands more than solid, the ink will move towards the flask with white surface.

[tianzhu]

chrisu:

Thanks Tianzhu. This really chim for P6. How to tell its elastic colision and not inelastic collision since it's not mentioned in question.

Hi Chrisu

Good Afternoon.

Here’s another site which may help.

Read the paragraph on “Elastic Collisions” (scroll down to the second paragraph).

http://www.sparknotes.com/testprep/books/sat2/physics/chapter9section4.rhtml

I think it offers a good explanation for our kids.

Best wishes