Particle Model and Pressure

Describe the motion of molecules in a gas

they are constant random motion

What factor affects the average kinetic energy of gas molecules?

• the temperature of the substance

• the higher the temperature, the higher the average kinetic energy

What effect does increasing temperature have on the pressure of a gas when held at constant volume?

pressure of the gas will increase as the temperature increases

Why does pressure increase as temperature increases (at a constant volume)?

• kinetic energy of molecules increases

• collisions between molecules becomes more frequent

• greater rate of change of momentum

• greater force and therefore pressure

If gas A is a low pressure, and gas B is at a high pressure, what can be said about the rate of collisions in each gas?

• there are more collisions per second in gas B than in gas A

• the rate of collisions is higher in B

Describe the force that the pressure of a gas exerts on the walls if its container

• the net force acts at right-angles to the containers surface

• the force increases as pressure increases

Explain how increasing the volume of a gas results in a decrease of pressure

• molecules become more spread out and so time between collisions increases

• the reduces the rate of collisions

• rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure

What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?

it is constant

p V = constant

What is the unit used for pressure?

pascal (Pa)

What increases when you do work on a gas?

• the internal energy of the gas

• this can also lead to an increase of temperature

Why does the temperature of air inside a bike pump increase when it is pumped?

• work is done on a gas when it is compressed

• doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules

• temperature increases with an increase of average kinetic energy