Q&A - PSLE Science

[ms_lim]

atutor2001:

ms_lim:

[quote=\"atutor2001\"]

If I follow the language used in the options very strictly, my answer will also be (2) because option (4) says that the candle is not strong enough - does not make sense. I am presuming that what they mean is that the \"flame of the candle\" is not strong enough.

The reason why (2) was not pick is because paper is a poor conductor of heat so it takes time to transfer heat to the water. Similarly, water is also a poor conductor of heat and will not remove heat from the paper very quickly. There is also no mention of the temperature of the water so I presume that it must be at room temperature. Therefore, heat transfer from the point on the paper (where the flame is applied) to the water will be very slow and the paper should get burnt. A more likely reason why it takes a while for it to get burnt should be that the flame of the candle is not strong enough.

(This question is quite similar to the one whereby a piece of paper is wrapped around a rod with one half made of wood and the other half made of iron. The paper wrapped around the wooden half will get burnt when a flame is brought to the centre of the rod before the iron part)

Dear atutor2001,

Thank your for explaining. Is the ans (2)? Personally I think this is a bad question. Please correct me if I am wrong.

Ya I also think it is a bad question. I will pick (4) as my answer (assuming that they mean to say that the flame is not strong enough) because the water being a poor conductor itself and the water is also at the same temperature as the paper, can offer little in helping to remove heat from the paper.[/quote]Dear atutor2001, :thankyou: for clearing my doubt.

[breanne]

On the topic of conductor of heat, I have a question on Pei Chun’s question 39b. Sorry could not post an image. The question asked which of 2 grills should be used so that the food is less burnt. The answer given was the grill with the thicker metal strips. If more heat is conducted away from the strips wouldn’t it mean that food gets mire heat so wouldn’t the food be more burnt ?

[ms_lim]

Verysuperkiasu:

ms_lim:

Please help to explain Qn #25 from Pei Chun 2011 Prelim, Ans key is 2 :


http://i55.tinypic.com/ehu0x.jpg\">

This was also my question.....the below article might help?

http://factoidz.com/boil-water-in-a-paper-cup/

Just scroll down a little

Dear Verysuperkiasu, :thankyou: for sharing

[atutor2001]

Verysuperkiasu:

This was also my question.....the below article might help?

http://factoidz.com/boil-water-in-a-paper-cup/

Just scroll down a little

Thank you very much for the information.

[Cockroach]

vidhyalog:

For the below OE - for part 1 - my son's answer reads \"the higher the temperature the more air bubbles will appear in the beaker and vice versa\". However I feel this is an observation - not hypothesis. The answer key says the hypothesis is that \"the higher the temperature the higher the rate of photosynthesis.' But my son insists they were told to use the variables provided to them to give the answers.


Would appreciate views on this. http://i53.tinypic.com/auyvd.jpg\">

I would write this for the hypothesis instead as your son's answer is not that accurate. (The number of air bubbles would increase as the heat intensity increases.) Your son's way of answering is only accepted if the questions is \" what can you conclude from the ......\" :what can you tell about the......\" etc

[Cockroach]

Please help



http://i52.tinypic.com/307w1eg.jpg\">

TIA( my son's answer is 4 but the model answer was 2)

[cimman]

Cockroach:

vidhyalog:

For the below OE - for part 1 - my son's answer reads \"the higher the temperature the more air bubbles will appear in the beaker and vice versa\". However I feel this is an observation - not hypothesis. The answer key says the hypothesis is that \"the higher the temperature the higher the rate of photosynthesis.' But my son insists they were told to use the variables provided to them to give the answers.


Would appreciate views on this. http://i53.tinypic.com/auyvd.jpg\">

I would write this for the hypothesis instead as your son's answer is not that accurate. (The number of air bubbles would increase as the heat intensity increases.) Your son's way of answering is only accepted if the questions is \" what can you conclude from the ......\" :what can you tell about the......\" etc

I would go with the answer key answer. The answer should link back to a topic within the PSLE syllabus, which in this case is photosynthesis. The hypothesis of the bubbles does not seem to achieve much in the way of an experimental objective, ie. there is no higher order objective. Yes, it explains the relationship between heat and the bubbles, but it begs the question, What causes the bubbles ? which is a higher order objective.

By putting in photosynthesis, and saying the the process producess gases both in the absence and presence of sunlight, the bubbles are explained and an additonal factor, ie heat, is brought to photosynthesis equation, in addition to sunlight.

[Tang]

cimman:

Cockroach:

[quote=\"vidhyalog\"]For the below OE - for part 1 - my son's answer reads \"the higher the temperature the more air bubbles will appear in the beaker and vice versa\". However I feel this is an observation - not hypothesis. The answer key says the hypothesis is that \"the higher the temperature the higher the rate of photosynthesis.' But my son insists they were told to use the variables provided to them to give the answers.


Would appreciate views on this. http://i53.tinypic.com/auyvd.jpg\">

I would write this for the hypothesis instead as your son's answer is not that accurate. (The number of air bubbles would increase as the heat intensity increases.) Your son's way of answering is only accepted if the questions is \" what can you conclude from the ......\" :what can you tell about the......\" etc

I would go with the answer key answer. The answer should link back to a topic within the PSLE syllabus, which in this case is photosynthesis. The hypothesis of the bubbles does not seem to achieve much in the way of an experimental objective, ie. there is no higher order objective.
By putting in photosynthesis, and saying the the process producess gases both in the absence and presence of sunlight, the bubbles are explained and an additonal factor, ie heat, is brought to photosynthesis equation, in addition to sunlight.[/quote]
Hi,

In my personal opinion, the answer provided by the pupil is perfect for this question.

The bubbles produced do not come from photosynthesis but respiration in this case.

Hypothesis may not be true and can be proven by the experiments.

[Tang]

atutor2001:

P5G:

Please help.


http://i56.tinypic.com/16jj4mg.gif\">


TIA.

I will pick (2) because its twisted look appears to be more suitable for clinging to tree trunks.

Hi,

I have done an online search for pictures of woodpecker, the photophoto shows that the correct answer should be (4).

[Tinkerbelle]

Verysuperkiasu:

ms_lim:

Please help to explain Qn #25 from Pei Chun 2011 Prelim, Ans key is 2 :


http://i55.tinypic.com/ehu0x.jpg\">

This was also my question.....the below article might help?

http://factoidz.com/boil-water-in-a-paper-cup/

Just scroll down a little

Interesting. Thanks for sharing, verysuperkiasu.