particle model and pressure

Describe the motion of molecules in a gas.

They are in 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 of the molecules

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 at 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 A than in gas B

● The rate of collisions is higher in A

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

● The net force acts at right-angles to the container’s 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

● This 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? (Higher)

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