Thank you for your help.

Q1)


Q2)


Which properties of the brown gas are shown by the above experiment?
A: It can be compressed.
B: It has no definite shape.
C: It has no definite volume.

A.A only
B.A and B only
C.B and C only
D.A, B and C only


Q3)
ID 15707
A football can hold 350 cm3 of air. Esther used a syringe and drew out 20 cm3 of air from the football. The volume of air in the football would be _______________.
A.350 cm3
B.330 cm3
C.350 cm3
D.370 cm3


Q1)Does the air’s mass remain the same or decrease? Why?
Q2)Does the experiment show that air has no definite volume,in addition to compressible and no definite shape?
Q3)Unlike a metal/plastic container, a football can be deflated or change its shape, does this affect the volume of air in it after air is drawn out? In this case, the amount of air drawn out is very small and should not cause the football to change shape; therefore volume should remain at 350cm3.Is this explanation logical?

Question 1
My answer is 1 - volume decreases and mass remains the same

Question 2
My answer is D - the properties of the gas are it can be compressed, gas has no definite shape, gas has no definite volume

Question 3
My answer is B - the volume decreased by 20cm3

More answers
Q1) The air's mass remains the same because it is the same amount of air just compressed.
Q2) Yes
Q3) I dont know

Hi there,

I would agree with 1 & 2 Xi Hui. For question 3, I would choose answer A or answer C (they are both 350).

Reasons:
For Q1)
- The air mass will remain the same and the volume will change. We know that one of the properties of a gaseous material is that its volume & shape can change while maintaining the same mass. Note: Out of interest not a part of P4 science this is a part of "Boyle's Law" relating to gas.

Q2)
- Yes the experiment does show this. Some additional observations / thoughts / questions
- Does the brown gas appear lighter or darker in colour?
- What happened to the air?

Q3)
Your explanation is logical. A football will change its shape depending upon the amount of air inside. However, a football is designed to maintain its "optimum" shape over a range of pressure incurred by the air inside. In this case, the air loss is approx 5% (20/350), which is marginal, and thus the shape will be maintained.

When "too much" air is pumped into the football, the shape will be lost (over inflated). When there is not enough air inside, it will become deflated. For this reason, footballs, basketballs, netballs, car tires, etc. all have a desired air pressure to perform at their best based on their physical design.

Additional questions / comments:
- Since the shape of the football remained constant, what changed as the air was drawn out?
- Could you kick the football farther or shorter when the football's air is replaced with another gas, say helium? What about if water replaced the air?

Additional questions / comments:
- Since the shape of the football remained constant, what changed as the air was drawn out?
- Could you kick the football farther or shorter when the football's air is replaced with another gas, say helium? What about if water replaced the air?

Let me try.
As air was drawn out, the football became lighter.
With helium gas, you should be able to kick the ball further.Helium is lighter than air.
With water in the ball, you can't bend it like Beckham.Water is much heavier than air,you can't kick it too far.

hi,siji
my answer to u:Q1:4
Q2 is D and Q3 is 1

Q1--this experiment shows air can be compressed.So the mass remains the same and the volume decreases. Q2--properties of air-air does not not have a definite shape and volume thus Q1 volume and shape remains too.air is immeasurable too!Air has mass and occupies space as it is a matter.
So come to the same as Q3.
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Hi

I wish to revisit this question again.

For Q2, does the experiment show that air can be compressed?
How does it show it?

Best Wishes

Hi Siji,

Yes the experiment does show that air can be compressed.

The first diagram shows that the gas can be compressed as it has only occupied the space in the jar (smaller volume compared to both the jar & the flask).

The second diagram shows that the gas occupied both the space of the jar and the flask (bigger volume compared to the vol of the jar only).

When seen from both the first and the second diagrams, not only can we conclude that air occupies any volume & any shape, we can also see that the gas can be compressed. See it from the perspective of the 2nd diagram to the 1st.

I hope this helps!

I agree with xi hui from Q1-Q3 and the other question I all dunno olady...haha!