Edexcel GCSE Physics 1PH0
Key Concepts of Physics
Motion and Forces
Conservation of Energy
Waves
Light and the Electromagnetic Spectrum
Radioactivity
Astronomy
Energy – Forces Doing Work
Forces and Their Effects
Electricity and Circuits
Static Electricity
Magnetism and the Motor Effect
Electromagnetic Induction
Particle Model
Particle Model
Pressure and volume of a fixed mass of gas
- 3 things to know
- Paper 2
Overview
Why compressing a fixed mass of gas at constant temperature raises its pressure and expanding it lowers the pressure, a blocked bicycle pump, the pressure × volume equation, and calculating new pressures, volumes and pressure factors.
What you need to know
Answer each one before you reveal it.
Explain why the pressure of a fixed mass of gas falls when the gas expands at constant temperature.
Explain why the average speed of the particles does not change when a gas is compressed at constant temperature.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Explain why reducing the volume of a fixed mass of gas at constant temperature increases its pressure.
Model answer
The particles have less space, so they strike the walls more often each second.
- 2
State what happens to the rate at which particles collide with the walls when a fixed mass of gas expands at constant temperature.
Model answer
It falls, because the particles travel further between collisions with the walls.
- 3
Explain why the pressure of a fixed mass of gas falls when the gas expands at constant temperature.
Model answer
Fewer collisions on each square metre of wall each second means a smaller average force per unit area.
- 4
Explain why the average speed of the particles does not change when a gas is compressed at constant temperature.
Model answer
The temperature sets the average speed of the particles, and the temperature has been kept the same.
- 5
The outlet of a bicycle pump is blocked and the plunger is pushed slowly halfway in. Describe what happens to the pressure of the trapped air.
Model answer
It roughly doubles, because the same number of particles is squeezed into half the volume.
- 6
State the two quantities that must be kept constant for the pressure of a gas to be inversely proportional to its volume.
Model answer
The mass of gas and its temperature.
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