Q&A - P4 Science

[ttyh]

[quote="atutor2001

In Primary school, I think they need to know this concept. That is, for a given volume of gas (at a given temperature and pressure), it can be pumped into a container of different size…
[/quote]

Again, I agree that gas can be pumped to fit into any given volume of the container. But I cannot concur that if I pump in 1cm3 of air into a 1000cm3 flask, and the question is pin pointing 'what is the volume of air after pumped into the flask" - and the answer is 1000cm3…

[Xiao Hu]

Hi atutor2001 and all gurus here,

Would you know whether any such similar question ever come out in the PSLE? What are the model answers given? Do these model answers give the similar answers, that the volume is the volume of the container?

I tried to search for "matter" and "volume" in the Primary Science Syllabus in the MOE website, but there is none that would help answer this question.

Thanks,
XiaoHu

[Xiao Hu]

ttyh:

[quote=\"atutor2001

In Primary school, I think they need to know this concept. That is, for a given volume of gas (at a given temperature and pressure), it can be pumped into a container of different size...

Again, I agree that gas can be pumped to fit into any given volume of the container. But I cannot concur that if I pump in 1cm3 of air into a 1000cm3 flask, and the question is pin pointing 'what is the volume of air after pumped into the flask\" - and the answer is 1000cm3...[/quote]

Hi there,
I think I found one similar question in one of the guidebooks, in pg 176 of PSLE Ultimate Science Guide from EPH. Applying that guide, mother777, Tianzhu and atutor2001 are correct, the volume of air is the volume of the container. The particular concept is \"the air particles are able to move about freely in the container\".

Thanks,
Xiaohu.

[chloecube]

Hi, got a question.


Compass needle points in the ________ direction.

Thks

[smartmummy]

chloecube:

Hi, got a question.


Compass needle points in the ________ direction.

Thks

North-south

[chloecube]

thks

[Zack7]

sry double post

[Zack7]

Zack7:

ttyh:

[quote=\"atutor2001

In Primary school, I think they need to know this concept. That is, for a given volume of gas (at a given temperature and pressure), it can be pumped into a container of different size...

Again, I agree that gas can be pumped to fit into any given volume of the container. But I cannot concur that if I pump in 1cm3 of air into a 1000cm3 flask, and the question is pin pointing 'what is the volume of air after pumped into the flask\" - and the answer is 1000cm3...

hi, you must first understand that the volume that air can occupy is not fixed

if i take 1cm^3 of air and put it into a container that is 1cm^3 in volume, then i have 1cm^3 of air

if i put it in 1000cm^3 volume of a container, then air will expand and fill up the entire volume.

now, you might ask why does air expands to fill the space?

this is a law of nature, where things tend to go to the lowest energy state(stability) . or in this case, it tends to maximize entropy ( which is the measure of disorderness)

in short, nature = chaos.

of course, when air has expanded so much until its density is so low, then it will be just like in the upper reaches of the atmosphere where the air is so thin that you can't breathe.[/quote]

[Zack7]

on 2nd thought, i think i understand what you are gunning at.


you now must understand the definition of volume of air.

if each marble represents a molecule of air , say 1 marble = 1cm^3

if we had 10 marbles, then when we put into 1000cm^3 of box, then yes, you are right, we only have 10 marbles and the volume of it is 10cm^3

but the definition of air takes into account the free space between the air molecules too.

this is why when the gas has spread into the container, it is said to have a volume of 1000cm^3.

[ttyh]

In what way is the large intestines and small intestines similar in terms of special features they have to facilitate absorption of materials?