3.3 Particle model and pressure
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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 and collisions between molecules become more frequent. Greater rate of change of moment, 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 gas 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 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. 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 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 it also increases the average kinetic energy of the molecules. Temperature increases with an increase of average kinetic energy.