1. Pressure and particles
What causes pressure in gases?
The particles of a gas are constantly moving around, and when they hit any surface they create a pressure on that surface.
The more often they hit a surface the higher is the pressure

2. Boyle’s Law
This law is about what happens to the pressure of a gas when the volume of a container changes and the temperature of the gas remains constant
The pressure depends on how often the particles hit the walls of the container
The more often, the higher the pressure, the less often the lower the pressure

3. volume is inversely proportional to pressure
Double the volume > halve the pressure
Halve the volume > double the pressure
volume is inversely proportional to pressure
Finishing Pressure = 1
Finishing Volume = 8
Starting
Pressure = 2
Volume = 4
Finishing
Pressure = 4
Volume = 2
Double volume
Starting volume
Halve volume

4. P1 x V1 = P2 x V2 What is the value of P x V for each result?
Results table
Starting
Pressure P1
Volume V1
P1 x V1
Finishing Pressure P2
Finishing V2
P2 x V2 2 4 8 1
What is the value of P x V for each result?
Answer = so:-
P1 x V1 = P2 x V2

5. The formula P1 x V1 = P2 x V2 is used to work out questions on Boyle’s Law.
P1 = starting pressure P2 = finishing pressure
V1 = starting volume V2 = finishing volume
Always start off the answer by writing down:
P1 x V1 = P2 x V2

6. A cycle pump contains 50 cm3 of air at a pressure of 100N/cm2
A cycle pump contains 50 cm3 of air at a pressure of 100N/cm2. Find its pressure if its compressed to 10cm2.
P1 x V1 = P2 x V2
100 x 50 = P2 x 10
5000 = P2 x 10
P2 = = 500 N/cm2 10

7. A mass of gas at a pressure of 20 Pa has a volume of 3m3
A mass of gas at a pressure of 20 Pa has a volume of 3m3. What will be the volume if the pressure is doubled?
P1 x V1 = P2 x V2
20 x 3 = 40 x V2
60 = 40 x V2
V2 = 60 = 1.5 m3 40

8. A balloon contains 8 litres of air at a pressure of 5 Pa
A balloon contains 8 litres of air at a pressure of 5 Pa. What is the new pressure of the balloon if its volume is decreased to 5 litres?
P1 x V1 = P2 x V2
5 x 8 = P2 x 5
40 = 5 x V2
V2 = 40 = 8 Pa 5

9. 100m3 of air is at a pressure of 75N/m2
100m3 of air is at a pressure of 75N/m2. If the volume of air is reduced to 30m3, what is the new pressure?
P1 x V1 = P2 x V2
75 x 100 = P2 x 30
7500 = P2 x 30
P2 = = 250 N/m 2 30