Kinetic Theory of Gases

Question 1

What are the 4 laws (postulates) which underpin kinetic theory of gases in an ideal gas?

Answer 1

1. Gases consist of a large number of particles (atoms or particles). These particles are spread out in a volume, the volume of the particles themselves are negligible to the total volume of the gas.
2. Particles travel in random directions at random speeds.
3. Particles move in a straight line until an abrupt collision. Particles collide with other particles, or surfaces. Collisions are perfectly elastic therefore ehn there is a collision the total kinetic energy does not change.
4. There are no attractive forces between particles.

Question 2

How to real gases differ from the 4 laws underpinning kinetic theory in an ideal gas?

Answer 2

Real gases occupy a small volume.

The gas particles exhibit attractive forces, these become more pronounced at low temperatures and high pressures.

Question 3

What is the formula for kinetic energy?

Answer 3

kinetic energy =1/2 x mv²

m = mass
v = velocity

Question 4

At a set kinetic energy how will the molecular weight of a atom/molecule effect the speed of the gas?

Answer 4

As the molecular weight increases then the speed will be reduced at a set kinetic energy.

Question 5

What is the relationship between temperature and kinetic energy of a gas?

Answer 5

Temperature is a reflection of the average kinetic energy of the particles of a gas.

Question 6

Using kinetic gas theory explain how pressure is exerted by a gas in a container?

Answer 6

As a gas particle collides with the wall of a container, as the collision is elastic it will bounce back in the opposite direction at the same speed.

As it is an 100% elastic collision its speed will be unchanged, however its velocity will have gone from +s to -s, the velocity change is 2s.

Acceleration is defined as change in velocity therefore with each collision there is acceleration.

Force = mass x acceleration. Therefore the mass of the particle x the acceleration is causing a force.

Pressure is defined as the cumulative force generated, divided by the total area over which that force is applied.

Therefore you can increase the pressure by reducing the area of the container or by increasing collisions (by increasing the temperature)