4.3.3 Particle model and pressure Flashcards
Describe the motions 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 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. 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
