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 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 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?

it is constant

pV = 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