Q&A - P3 Science

[Lynn2]

Hi Tianzhu


Thanks for the link and explanation...you have taught me so much...thank you.

rgds

tianzhu:

Hi

Q28) Follow these links, they should help to address your query on dragonfly.
http://www.dragonfly-site.com/dragonfly-life-cycle.html
http://www.blithfieldeducationcentre.co.uk/kp/environmentpages/dragonfly_life_cycle.htm

For Q16, option(3) is a logical answer.
D and A are pretty obvious, they are nearer to the heat source. B will be the next one because it is found in the same bar, allowing heat to reach it first as compared to C. As for C, heat has to be conducted through the T junction; therefore a longer time is needed to melt the wax than B.

[tianzhu]

Hi


For the third statement, Towel B will absorb the most amount of water.
My take is not possible to tell.

This experiment is to show whether the exposed area of a towel affects the rate of evaporation. For a fair test, the amount of water absorbed by the towels must be the same at the starting point.

The question did not show how the towels get wet, that is, how the towels are dipped in water.

Consider scenario1 – The towels are folded first as in A,B,C and D before dipping into a container of water big enough to accommodate a fully stretched out one, Towel B. In this case, there is a likelihood of Towel B absorbing the most amount of water as compared to the others because of a larger exposed area.

Consider scenario 2 – The towels are dipped in exactly the same way. In this way, the chance of all towels absorbing the same amount of water is high. In both scenarios, the duration remains the same.

As for the last statement, the key word lies in based on the experiment above. From background knowledge, we know that higher wind speed increases the rate of evaporation. But, there is no mention of wind speed in this question, so we cannot infer that the wind caused the rate of drying to increase.

Maybe to elaborate further, consider a real life example.
Lucy has a beautiful daughter. Let’s call her Linda
Linda appeared in a dialogue on radio. She spoke eloquently in a clear and sweet voice.
Based on the radio programme, for listeners (yet to see Lucy’s daughter), they can only say that Linda spoke well and has a sweet voice. I am not sure whether this is a good example but hope it’ll help you.

For these types of questions, we have to exercise caution not to input background knowledge.

Best wishes.Have a nice weekend.

[tianzhu]

Hi

[quote]Question 44 why there is no change in water level after the beakers are out in the sun for four hours when there are different rate of evaporation takes place?[/quote]Yes, if you look carefully, you can see that there is an attempt by the the answerer of the WS to differentiate the differences in the level of liquids.
The 150 cubic cm is just an indication on the measuring cylinder. Look at those measuring cylinders you used for cooking, I am sure you can see those markings.

The concept is more evaporation means less remaining liquid. Apply it; A has the lowest remaining level, followed by C and B

[Joy]

Thanks tianzhu


Regarding this three liquid , not sure why all are at same level as an answer.Could there be an error?

You too have a great weekend...

cheers

tianzhu:

Hi
[quote]Question 44 why there is no change in water level after the beakers are out in the sun for four hours when there are different rate of evaporation takes place?

Yes, if you look carefully, you can see that there is an attempt by the the answerer of the WS to differentiate the differences in the level of liquids.
The 150 cubic cm is just an indication on the measuring cylinder. Look at those measuring cylinders you used for cooking, I am sure you can see those markings.

The concept is more evaporation means less remaining liquid. Apply it; A has the lowest remaining level, followed by C and B[/quote]

[tianzhu]

Joy:

Regarding this three liquid , not sure why all are at same level as an answer.Could there be an error?

Hi Joy

If you take look at the given answer, you’ll see that for cylinder A, the liquid level is at the second marking. However for B and C, the differences in levels are not so contrasting. Just take the 150 cubic cm reading as a marking on the external surface of the cylinder.

Take a look at those measuring cylinders you use for cake making. They also have markings on the cylinders for measuring purposes.

[Tang]

Lynn2:

Hi Tang


Thanks for the pointers.

Do you mind link up how this :melting point (deg cel) Boiling point(deg cel)
p 0 85
q -30 110
r -40 15
s 80 200

I am not able to explain to my girl based on the info you gave...maybe you can tell me how?thanks

Tang:

[quote=\"Lynn2\"]Hi Tianzhu
Can someone explain to me on the co relation between the three states in relation to room temperature as illustrated in the questions.

Solid state - Temperature below Melting point

Liquid state - Temperature between Melting point and Boiling point

Gaseous state - Temperature above Boiling point.

Room temperature is below 30 degree C (about 28 degree C)

Based on above, P, Q, R and S are Liquid, Liquid, Gas and Solid respectively at room temperature. Hence answer is (1).

[/quote]
melting point (deg cel) Boiling point(deg cel)
p : 0 .................... L (28 ) ..................... 85
q : -30 ................. L (28 )..................... 110
r : -40 ................... 15...................... G (28 )
s : S (28 ) ............... 80 ........................ 200

[Lynn2]

Thanks , Tang, that was exactly why I bingo with that....

Tang:

Lynn2:

Hi Tang

Thanks for the pointers.

Do you mind link up how this :melting point (deg cel) Boiling point(deg cel)
p 0 85
q -30 110
r -40 15
s 80 200

I am not able to explain to my girl based on the info you gave...maybe you can tell me how?thanks
[quote=\"Tang\"]Solid state - Temperature below Melting point

Liquid state - Temperature between Melting point and Boiling point

Gaseous state - Temperature above Boiling point.

Room temperature is below 30 degree C (about 28 degree C)

Based on above, P, Q, R and S are Liquid, Liquid, Gas and Solid respectively at room temperature. Hence answer is (1).

melting point (deg cel) Boiling point(deg cel)
p : 0 .................... L (28 ) ..................... 85
q : -30 ................. L (28 )..................... 110
r : -40 ................... 15...................... G (28 )
s : S (28 ) ............... 80 ........................ 200[/quote]

[Lynn2]

Hello all


Could not sleep at this wee hour and is thinking how to go about doing this, can anyone help...

http://www.wendykoh.com/08/primary4-acssa2-science.pdf
Question 40

I dont understand how different angle affect the postion of the shadow.For this case, I totally cannot see it.

thanks

[Lynn2]

Earlier part of the day, I did try to read up on this topic, the book mention something like cross section of the object…which I cannot really digest.

[tianzhu]

Lynn2:

Earlier part of the day, I did try to read up on this topic, the book mention something like cross section of the object...which I cannot really digest.

Hi

The simplest way to see what is a cross section of an object. Take an apple and cut into two halves, look at the white portion, which is the cross section of an apple.

http://aggie-horticulture.tamu.edu/syllabi/201h/ediblebotany/applecut.html