Q&A - P4 Science

[jedamum]

verykiasumummy:

jedamum:

[quote=\"tianzhu\"]
Hi

Good Morning.

I think students learned that a gas has no definite volume and that it can be compressed in PSLE science.

Going back to your question, I think the answer lies in the state of the basketball before air is pumped in.

1)If it is in the deflated state, as you pump in more air, the shape of the basketball changes, hence volume increases.

2)If the basketball is already pumped to its recommended pressure, then pumping in more air may not increase its volume. The shape of the ball does not change. You can imagine the ball as similar to a container of fixed volume.

Best wishes

so Nebbermind same view as Tianzhu? :?
if yes..it is 2 against 2 already.
for me, i dunno. keen to find out. thanks!

hi jedamum, was there any previous debate over this that i missed out?[/quote]there was some discussion about matter/pressured air in the earlier pages that i did not read in detail as it was too technical.not sure if it was related to this.

[jedamum]

atutor2001:

verykiasumummy:

..


...in fact, it does not matter if it is a ball or not, whether it was deflated or inflated. pri students only need to know that air can be compressed while at the same time space out to occupy a bigger space. even though the ball may not be round as it is not fully inflated, the volume of air inside is still 400cm3, (same as capacity of ball), even though inly 350cm3 is pumped inside.

If this is a PSLE question, do not interpret it this way. In PSLE, real life practical experience must be applied to interpret all questions.

atutor2001
what is your view on the deflated soccer ball that is not pumped to full capacity? is its volume still 400cm3'?

[atutor2001]

jedamum:

atutor2001
what is your view on the deflated soccer ball that is not pumped to full capacity? is its volume still 400cm3'?

I share the same view that the volume of a deflated ball is less than 400 cm3.

I remembered using the plastic bag as an example when explaining to my children. Each plastic bag has a certain maximum capacity if completely filled with air. However, for a brand new plastic bag (just taken out from its packing), the volume of air inside = 0 cm3.

[verykiasumummy]

there was once this question in my ds1’s paper. 2 containers capacity of 600cm3 attached with an air pump each, container A has 100cm3 more air pumped in, the new volume of air inside is still 600cm3 because air can be compressed.


for container B, 200cm3 of air is pumped out, what is the volume of air in the container and why?

the ans is, still 600cm3, because air can space itself out to occupy the same space of the container because air has no definite volume.

i would apply the same to this question.

[Nebbermind]

Container has fixed shape n volume. Inflatable objects do no have fixed shape or vol UNTIL they reach they final capacity.

[verykiasumummy]

Nebbermind:

Container has fixed shape n volume. Inflatable objects do no have fixed shape or vol UNTIL they reach they final capacity.

yup u r right... much as i sometimes disagree with some of the answers given, i learnt to forgo about the \"think too much\" logic so as to accept those answers in order to teach my dc... i still hv 2 more to go for psle, so i have to stand by firm with the concepts to teach them...

using a container that has fixed shape and volume, the concept is quite clear cut. i would only say that the setter of the question wants students to apply same logic for the case of the deflated ball.

[Nebbermind]

That’s why I usually donch trust those assessment books as I feel that their questions are not thought thru thoroughly and they even recycled questionable questions!!

[verykiasumummy]

Nebbermind:

That's why I usually donch trust those assessment books as I feel that their questions are not thought thru thoroughly and they even recycled questionable questions!!

they dun proof read into the questions that much... that's why the same problem persists...

i do understand that for a deflated ball, since capacity is 400cm3, when only 350cm3 is inserted, the ball may not be fully round yet, and as air does not have the pushing force to round the ball, the volume of air inside should depend on how inflated or deflated the ball is at that moment..

i learn to forgo those anyway... no point wasting time to think too much to outsmart the teacher or setter. might as well spend more time instilling correct concepts in my dc...

[sleepyqueen]

tayobus:

http://i49.tinypic.com/2aont0.jpg\">


Dear All,
My child is doing the past year paper and when come to the above question, he said not his level topic and he found out from the PSLE Science guide book it is upper block topic. Can anyone advise does your P4 child learnt the above? How do your child answer the above? By the way, this is taken from Nan Hua Pri SA2 2011 paper.

:thankyou:

Hi all,
I think this question not necessary be the upper level one as the kid are taught in p3 that flower will change colour if dip in coloured water. Now the stem is cut into 2 and soaked in different coloured solution. P3 the kids are also taught that roots take in water and the stem transport it to the other parts of the leaves.

[sleepyqueen]

milomilo:

Help needed:


Gopal pumped air into 2 footballs. The footballs when fully inflated each have a capacity of 400cm3. For football A, he pumped 350cm3 into it and for football B he pumped 405cm3. Which of statement is correct?

(1) Ball A is heavier than Ball B
(2) Ball B has 405cm3 of air inside it
(3) Both Ball A and B has 400cm3 of air inside it
(4) Ball A and Ball B are of the same mass after air was pumped in.

Note: Answer (1) and (4) are obvious wrong.

Thanks!

this question my answer is 3 as the volume 400cm3 is fixed cannot change.