Q&A - P4 Science

[jedamum]

Thanks smartmummy!

[rrjan]

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Hi, could any science guru kindly explain this question to me? Answe from school is 4, but my son's answer is 3. Thought that since water has a definite volume and took up 50 cubic cm of fixed space, since container A has a volume of 120 cubic cm, then the amount of air that can occupy the container will be 70cubic cm? :idea:

[Nebbermind]

P4 syllabus teaches that gas can be compressed. So u can put 100cm3 of oxygen into a smaller volume of space.

[fightingmom]

Yah… what Nebbermind explains is right

[chloecube]

my answer is nos 4 too.


DS’s mock science paper came out with similar question like this too

explaination : air can be compressed

[rrjan]

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Thanks for all the kind explainations. Could someone kindly help me with this question then.

Very similar question, but it was a past year's top school exam paper. My son is still quite confused with how to answer such question, cos he says that if there is no fluid, in the container, then the container would be able to accomodate any volume of air (air can be compressed), but if it is filled with a definite volume of fluid say 200 cubic cm(as for this past year question) , would the container still accomodate any volume of air or just the remaining volume of the container?? :scratchhead: :?:

[Nebbermind]

Yes, no matter how many times you pump, the volume of air will remain as the volume of the remaining space in the container, ie, 300cm3.


Answer will be something along this line…gas has no definite volume and can be compressed.

[rrjan]

Hi nebbermind, thank you for your very prompt explaination. Now I am just as confused as my son. :? why is it that in this question, the amount of air that the container can accomodate is 300 cm3, while in my earlier question, all 3 containers will be able to accomodate 100 cm3 of air? Thought that container A which only has a capacity of 120 cm3 would be able to accomodate only 70 cm3 of air?


Apologise for all my questions cos I myself is not too good at Science.

[Nebbermind]

When dealing with such kind of question that involves compression of air/gas, always look at the PHYSICAL volume.


The PHYSICAL volume will always be the remaining space (air space shown in diagram) inside the contrainer, ie, if u squeeze 1000cm3 of air into a 100cm3 container, the air volume will be 100cm3.

[rrjan]

hmm, understand that concept, but if the container has liquid in it (which already takes up some space?) as in question 1, then does it not mean that the physical volume to accomodate the air is compromised? AS such for question 1, why is it that container A is still able to hold 100 cm3 of oxygen if the total Capacity of the container is 120cm3 and it already has 50 cm3 of water in it?