Topic 3- Particle model and pressure

Question 1

Describe the motion of molecules in a gas

Answer 1

They are in constant random motion

Question 2

What factor affects the average kinetic energy of gas molecules?

Answer 2

The temperature of the substance
The higher the temperature, the higher the average kinetic energy of the molecules

Question 3

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

Answer 3

Pressure of the gas will increase as the temperature increases

Question 4

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

Answer 4

-Kinetic energy of molecules increases
-Collisions between molecules becomes more frequent
-Greater rate of change of momentum
-Greater force and therefore pressure

Question 5

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

Answer 5

-The net force acts at right-angles to the container’s surface
-The force increases as pressure increases

Question 6

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

Answer 6

-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

Question 7

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

Answer 7

It is constant
p V= constant

Question 8

What is the unit used for pressure

Answer 8

Pascal (Pa)

Question 9

What increases when you do work on a gas?

Answer 9

-The internal energy of the gas
-This can also lead to an increase of temperature

Question 10

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

Answer 10

-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