Q&A - PSLE Science

[P5G]

Please help.


http://i51.tinypic.com/30hx75k.gif\">


The air in the flask gains heat from the hot water and expands pushing the coloured water up the tube.

The coloured water gains heat from the hot water and expands and moved up the tube.

Please advise which answer is correct.


TIA.

[P5G]

Please help.


http://i53.tinypic.com/2ytuyyd.gif\">


TIA.

[ms_lim]

vidhyalog:

atutor2001:

[quote=\"vidhyalog\"]


I agree with your DD's answer. Any others who think differently?

There are 3 variables : material; flame; temperature of water

If both the flame and temperature of water are the same but the pots are of different material, then A is correct i.e. material A is a better conductor of heat which allow faster heat transfer to boil more water using the same time as B.

If both the material and temperature of water are the same but the flame sizes are different, then B is correct i.e. pot B has weaker flame and needs the same time as A to boil less water.

If both the material and flame size are the same but the temperatures of the water are different, then C is wrong because A will take a even longer time because it has more water at lower temperature.

Yes I agree with you.

(I was putting my thoughts into words - that is why so lengthy - hope it is of help to PSLE students on the analysis process)

Hi atutor,

You have indeed expressed it well. I was trying to convey this to my son moments ago. Will let my son read and see if he can be convinced.

He felt even if A had water of lower temperature, if the B was poor conductor and/or had low flame - that could explain why the time was the same for boiling. So he kept saying, it is possible. Nobody said I must keep the other 2 variables constant. I was trying to argue that he would have used the pricinple of keeping the other 2 variables constant to evaluate Scenarios A and B, so would have to do the same for C. But I had to stop discussing it as he was close to tears.

I hope the PSLE paper will not have too many ambiguous questions.[/quote]Dear atutor2001 and vidhyalog, thank you.

[ms_lim]

ck123:

ms_lim:

http://i56.tinypic.com/vdhft4.jpg\">

Ans key : (2), dd's ans : (3)

Answer should be 3 cause it should repel and not attract with both N

Dear vidhyalog and ck123, thank you.

[ms_lim]

atutor2001:

ms_lim:

http://i51.tinypic.com/20fqp1k.jpg\">

Ans key : (2), dd's ans : (3)

This type of question is very difficult because we must analyse and come out with a conclusion, strictly using only the data given. We must NEVER use any of our personal knowledge!

Case 1 : plastic bowl -> weight & size & material; 15th floor -> height
Case 2 : flower pot -> weight & size & material; 2nd sty -> height
Case 3 : beer bottle -> weight & glass & material
Case 4 : flower pot -> weight & size & material

Therefore, I will say that the data do provide information on weight, size, material and height. However, there is no information on \"hardness\" of each material (don't use your own knowledge).

My answer will than be A (size), B (mass) and D (height).
But there is no A,B,D so the next best one is B,D

(don't get worried that the analysis process is so tedious - it appears tedious only in words. The actual mental process is actually quite fast. Important point to note is \"use only information from the question; no personal knowledge is allowed\")

Dear atutor2001, thank you for your advise. I will ask my dd to pay attention to such tricky question.

[ms_lim]

vidhyalog:

Dear Andante and vidhyalog, my dd argue that there is no egg in plant but only ovule.

Hi ms_lim,
Thx for your clarification. \"paiseh\", no wonder my dd insisted on the answer(2) i.e. ovule :)[/quote]


Hi - I got this from one of the text books. In the diagram - the ovule is shown to contain egg cell. Would appreciate if anyone else could help clarify. http://i53.tinypic.com/33f3odt.jpg\">

Thanks[/quote]
Dear vidhyalog, I refer to the sci textbook and it also shows that ovule contains egg cell. Thus, I am confused now what is the female reproductive cell in plant ie Egg or Ovule. Hope some kind soul can help to confirm.

[SUPERCKJ]

Anybody did the 2011 RGPS Prelim Science MCQ.


Qustion 28 with a test tube at the top part and an ice protected by metal gauze.

Question: Which one best explains why ice at the bottom tube takes a longer time to melt?

Is the ans 4? Metal gauze prevent heat from reaching the ice.

[bcs-dad]

atutor2001:

bcs-dad:

Hi All,


For the following question, I thought the answer should be 1) A only. My DS also think the same way. But the answer key says the right answer is 2) A and D

http://i56.tinypic.com/2pqn7dk.png\">

For setup D, I thought there is not way for the water to evaporate from second tube while some water can be evaporated from the first one. But for setup A, the the amout to water that can be evaporated can be same..

Can some body help me why 2) is correct than 1) ??

I share the same answer as you.

My reasoning is as follows :
For any experiment conducted, we must ensure that it is a fair test (implicitly \"understooded\")
For a fair test, only 1 variable can be changed.
For D, there are 2 variables that have been changed. (therefore not fair test)
(in experiment, we cannot allow any possible source of error and the easiest way is to stick closely to the requirement that only 1 variable is changed)

Thanks atutor2001 and tianzhu for your suggestions..

[P5G]

SUPERCKJ:

Anybody did the 2011 RGPS Prelim Science MCQ.


Qustion 28 with a test tube at the top part and an ice protected by metal gauze.

Question: Which one best explains why ice at the bottom tube takes a longer time to melt?

Is the ans 4? Metal gauze prevent heat from reaching the ice.

Hi Uncle/Auntie SUPERCKJ,

The answer is (3) Water conducts heat away slowly.

[atutor2001]

vidhyalog:

vidhyalog:

Hi - Could I confirm if the answer for this question is :



Abdomen and Thorax only or Head, abdomen and Thorax or anything else. http://i51.tinypic.com/i2sm8k.jpg\"> aa

For such question, I always try to find the answer from the picture by \"spotting the differences\" :

tentacle becomes antennae
simple eye becomes compound eye
mouth becomes proboscle
true leg becomes leg
nothing becomes wings
shape of head, thorax, abdomen becomes different
proleg disappeared

So my answer is true leg is the part that that did not change.