AQA GCSE PHYSICS · PAPER 1 · HIGHER TIER ONLY
Exam Practice: Increasing the pressure of a gas
Increasing the pressure of a gas · Particle model of matter · Lesson 6 of 6 · 14 marks · 15 minutes
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Instructions
• Answer all the questions.
• Write your answers in the spaces provided.
• The marks for each question are shown in brackets - use this as a guide to how much to write.
• The answers are on separate pages at the back. Attempt every question before you look at them.
• Answer all questions. Use the mark allocation as a guide to how much to write.
Question 1 EXPLAIN (3 marks)
A student uses a bicycle pump to inflate a tyre and notices that the pump becomes warm. Explain why.
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(Total for Question 1 = 3 marks)
Question 2 STATE (2 marks)
What is meant by work done?
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(Total for Question 2 = 2 marks)
Question 3 EXPLAIN (4 marks)
A gas in a sealed syringe is compressed quickly by pushing in the plunger. Explain, using the particle model, why the temperature of the gas rises.
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(Total for Question 3 = 4 marks)
Question 4 EXPLAIN (2 marks)
Explain why a gas compressed slowly and allowed to cool would not stay hot.
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(Total for Question 4 = 2 marks)
Question 5 DESCRIBE (3 marks)
Describe the energy changes when a gas is compressed by a piston and then allowed to expand pushing the piston out.
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(Total for Question 5 = 3 marks)
TOTAL FOR PAPER = 14 MARKS
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Answers and mark scheme
Check your answer only once you have written one.
Question 1 (3 marks)
Work is done on the air by the force on the piston. This transfers energy to the air, so the internal energy of the air increases and the temperature rises, warming the pump.
• Work is done on the gas 1 mark
• Internal energy of the gas increases 1 mark
• Temperature rises 1 mark
Question 2 (2 marks)
The transfer of energy by a force.
• Transfer of energy 1 mark
• By a force 1 mark
Question 3 (4 marks)
The force on the plunger does work on the gas. Energy is transferred to the gas particles, so the average kinetic energy of the particles increases. The temperature of the gas depends on the average kinetic energy, so the temperature rises.
• Work is done on the gas 1 mark
• Energy transferred to the particles 1 mark
• Average kinetic energy increases 1 mark
• So the temperature rises 1 mark
Question 4 (2 marks)
The energy is transferred by heating to the surroundings, so the internal energy and temperature of the gas decrease.
• Energy transferred to the surroundings 1 mark
• Internal energy or temperature decreases 1 mark
Question 5 (3 marks)
When compressed, work is done on the gas so its internal energy increases. When it expands and does work on the piston, its internal energy decreases and it cools.
• Work done on the gas: internal energy increases 1 mark
• Gas does work on the piston when expanding 1 mark
• Internal energy decreases 1 mark