AQA GCSE PHYSICS · PAPER 1 · HIGHER TIER ONLY
Increasing the pressure of a gas
Particle model of matter · Lesson 6 of 6
Warm-up
Answer each one, then check.
1. What is work done?
Energy transferred by a force
2. What is internal energy?
Total kinetic and potential energy of the particles
3. What is the link between temperature and particle energy?
Higher temperature means more kinetic energy
4. What happens to gas pressure when volume decreases?
It increases
5. What is a force?
A push or a pull
Learning Objectives
1. Define work as the transfer of energy by a force.
2. Explain that doing work on a gas increases its internal energy.
3. Explain why the temperature of a gas rises when it is compressed, for example in a bicycle pump.
Work On A Gas (Higher Tier)
Work is the transfer of energy by a force. Doing work on a gas increases the internal energy of the gas and can cause its temperature to rise.
This is why a bicycle pump gets warm when used.
A Bicycle Pump
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Work done becomes internal energy. |
A bicycle pump with the handle pushed in, doing work on the air and warming it.
Why the Gas Warms
A chain of ideas.
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1 Push the piston You apply a force that moves the piston: work is done on the gas. |
2 Energy transferred The energy is transferred to the gas particles. |
3 Kinetic energy increases The particles move faster. |
4 Temperature rises The average kinetic energy of the gas increases. |
Bicycle Pump
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Explain why the barrel of a bicycle pump gets hot when the pump is used to inflate a tyre. |
1. Work done
The force on the piston does work on the air inside
2. Internal energy
The internal energy of the air increases as the energy is transferred to its molecules
3. Temperature
The temperature of the air rises, and thermal energy is transferred to the barrel
Answer: Work is done on the air, increasing its internal energy and temperature, which warms the pump.
Exam Points
How to score the marks.
▸ Say 'work is done'. Name the force and the energy transfer.
▸ Link to internal energy. Increase in internal energy of the gas.
▸ Link to temperature. Average kinetic energy of the molecules increases, so temperature rises.
Key Terms
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Work Energy transferred by a force. |
Internal energy Total kinetic and potential energy of particles. |
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Compression Squashing a gas into a smaller volume. |
Molecule A group of atoms bonded together. |
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Enclosed gas A gas trapped in a container. |
Temperature A measure of average kinetic energy. |
Your Task: Warm Pump
8 minutes
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You pump up a tyre and the base of the pump gets warm. Explain why using the ideas of work and internal energy. 1. Say what is being done to the gas. 2. Link to temperature. |
A good answer shows: Work is done on the air by the force pushing the piston. This increases the internal energy of the air (kinetic energy of the molecules), so the temperature increases and the pump warms.
Can I...?
☐ Define work.
☐ Explain work on a gas.
☐ Link work to internal energy.
☐ Link internal energy to temperature.
☐ Use the bicycle pump example.
☐ Write a clear chain of reasoning.
☐ Use the correct terms.
☐ Explain warming.
Summary
✓ Work is energy transferred by a force.
✓ Work done on a gas increases its internal energy.
✓ The temperature of the gas increases.
✓ Example: a bicycle pump.
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EXAM FOCUS Explain why the air in a bicycle pump gets hotter when the pump is used. (3 marks) Work is done; internal energy rises; temperature rises. |