Q&A - PSLE Science

[Full.010894Cream]

tianzhu:

elkniwt:

Hi,


Referring to Q24 of this paper http://www.orlesson.org/orp/09Sc/2009-Sc-CA1-MahaBodhi.pdf

Need some help to understand why the answer is (3) A and C only [I thought it is (4) cos if evaporation has taken place, then there will a reduction in volume as well as a reduction in weight.] Some advices please. Thanks!

Hi

In primary science, students learned about the three states of water. They are solid(ice),liquid(water) and gas (steam or water vapour).

In this question, substance X is not labelled. Students who are familiar with States of Matter should be able to see that there is a change of state from solid to liquid. Naturally, the change from ice to water may come to mind as this is probably the only example in their primary science textbook (as far as I can remember while going through my boy’s book last year).

You have correctly pointed out that there will be evaporation. However, the key point is here is what you observe after two hours. Undeniably, the liquid evaporates, but the amount may be insignificantly or too negligible for us to see noticeable changes in weight.Hence option (3) is a logical answer based on the context in the question.

However if the question states that the set up is left overnight, I’d venture to say that there will be change of weight as the amount of water evaporated may be significant enough to influence the weight.

Best wishes

The change in volume is due to change in temp (expand when warm?)?

[Sun_2010]

Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


http://www.postimage.org/image.php?v=PqaRCVS

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

[Sun_2010]

http://www.postimage.org/image.php?v=Tsxb3Bi



Just wanted to check on this question from 2009 Rosyth SA2 p6 (Q30)

Is The pollution caused by biodegradeable material considered a -ve impact of waste?

[mummyjoyce]

Sun_2010:

Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


http://www.postimage.org/image.php?v=PqaRCVS

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

1 is definately out; so best choice is 3

[ruyu]

Sun_2010:

Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


http://www.postimage.org/image.php?v=PqaRCVS

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

Yep checked it is 1

[ruyu]

Sun_2010:

http://www.postimage.org/image.php?v=Tsxb3Bi



Just wanted to check on this question from 2009 Rosyth SA2 p6 (Q30)

Is The pollution caused by biodegradeable material considered a -ve impact of waste?

Yeah it is.

[Tang]

mummyjoyce:

Sun_2010:

Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


http://www.postimage.org/image.php?v=PqaRCVS

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

1 is definately out; so best choice is 3

Hello,

A is the changed variable.

D is the result you measure (so cannot be kept constant.

So variables to be kept constant are B and C. Hence no correct answer provided.

[ruyu]

Tang:

mummyjoyce:

[quote=\"Sun_2010\"]Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


http://www.postimage.org/image.php?v=PqaRCVS

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

1 is definately out; so best choice is 3

Hello,

A is the changed variable.

D is the result you measure (so cannot be kept constant.

So variables to be kept constant are B and C. Hence no correct answer provided.[/quote]no it cant be b as they did not say that if the texture of the ramp affected the distance travelled by the ball. So you will have to change the length of the ramp. So the answer is 1.

[ruyu]

Tang:

mummyjoyce:

[quote=\"Sun_2010\"]Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


http://www.postimage.org/image.php?v=PqaRCVS

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

1 is definately out; so best choice is 3

Hello,

A is the changed variable.

D is the result you measure (so cannot be kept constant.

So variables to be kept constant are B and C. Hence no correct answer provided.[/quote]no it cant be b as they did not say that if the texture of the ramp affected the distance travelled by the ball. So you will have to change the length of the ramp. So the answer is 1.

[Nebbermind]

since you cannot change A (books) without changing (C) the position of the car, the only other thing u can change is B.


BTW, if u change A and keep B constant, both height of car and slope (angle) will change, therefore C will not hold.