Question
(a) In terms of the momentum of molecules, explain how a gas exerts pressure on the walls of its container. [4]
(b) A fixed mass of gas of volume V1 is at a pressure p1. It is compressed to a volume V2.
Complete the equation for the final pressure p2 of the gas when the gas is compressed at constant temperature.
p2 = [2]
State and explain how the final pressure compares with p2 when the temperature of the gas increases during compression.
statement …………………………………………………………………………………………………………..
explanation ………………………………………………………………………………………………………… [3]
[Total: 9]
Answer/Explanation
Ans:
(a)
molecules strike walls
momentum (of molecules) changes / momentum = mass× velocity
force = rate of change of momentum
pressure = (sum of) force(s) / area / pressure = rate of change of momentum / area
(b)
(i)
(p2=)p1V1 / V2
p1V1 =p2V2 )
(ii)
greater
molecules move faster / have greater KE / molecules have greater momentum
(leads to) more frequent / harder collisions (with walls) / great rate of change of momentum