Kinetic Theory & Ideal Gases (Edexcel A Level Physics)

Exam Questions

14 mins2 questions
1a
Sme Calculator
2 marks

For an ideal gas p V space equals space N k T and p V space equals space 1 third space N m space less than c squared greater than.

Use these relationships to show that the mean kinetic energy of a gas molecule is proportional to the absolute temperature.

1b
Sme Calculator
3 marks

The molecules in a sample of gas have a mass of 5.0 × 10-26 kg.

Calculate the root-mean-square speed of gas molecules in the gas at 25 °C.





Root-mean-square speed = ...................................

Did this page help you?

2a
Sme Calculator
3 marks

The photographs show a wooden pop gun before and after the cork is popped.

q18-nov-2021-9ph0-02-edexcel-as-a-level-phy

The diagram shows a cross-section through the pop gun.

q18-1-nov-2021-9ph0-02-edexcel-as-a-level-phy

Initially the piston is at the right-hand end of the cylinder, as shown. Then the cork is pushed into the other end of the cylinder.

When the handle is pushed in, the pressure of the air in the cylinder increases. This exerts an additional force on the cork.

Once the additional force is sufficient to overcome the frictional force between the cork and the cylinder, the cork is pushed out.
Show that the pressure of the air in the cylinder must be about 2 × 105 Pa in order to push the cork out.

   maximum frictional force = 8.8 N
   cross-sectional area of cork = 9.2 × 10−5 m2
   atmospheric pressure = 1.0 × 105 Pa

2b
Sme Calculator
2 marks

Calculate the temperature of the gas in the cylinder at the instant the cork is expelled.
volume of air in the cylinder with the handle pulled out = 1.1 × 10−5 m3
volume of air in the cylinder at the moment the cork is pushed out = 6.7 × 10−6 m3
atmospheric pressure = 1.0 × 105 Pa
initial temperature of air = 19°C


Temperature = ....................................................................

2c
Sme Calculator
2 marks

The formulae sheet for this paper includes the equation

              p V space equals space 1 third N m open angle brackets c squared close angle brackets

Derive the equation 1 half m open angle brackets c squared close angle brackets space equals space 3 over 2 k T

2d
Sme Calculator
2 marks

Calculate the root mean square speed of the molecules of air in the cylinder before the handle is pushed in.
   average mass of molecule of air = 4.8 × 10−26 kg
   temperature of air = 19°C

Root mean square speed = ....................................................................

Did this page help you?