AQA GCSE Physics
AQA GCSE Physics 4.3.3 Particle Model and Pressure Exam Questions
Free AQA GCSE Physics exam questions for 4.3.3 Particle Model and Pressure, with a mark scheme for every pack. Covers gas particle motion, how temperature and volume affect gas pressure, pV = constant, and doing work on a gas.
4.3.3 Particle Model and Pressure exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Physics 4.3.3 Particle Model and Pressure
This AQA GCSE Physics section applies the particle model to gases. All students need to explain how the temperature of a gas relates to the average kinetic energy of its molecules and why raising the temperature at constant volume increases pressure. Pressure in gases at constant temperature (pV = constant) is physics only, and increasing the pressure of a gas by doing work on it is physics only and Higher tier only. It is examined on Paper 1. Examiners want explanations in terms of molecules colliding with container walls and the force per unit area.
What you need to know
- Particle motion in gases The molecules of a gas are in constant random motion. The temperature of the gas is related to the average kinetic energy of the molecules.
- Temperature and pressure Increasing the temperature of a gas held at constant volume increases the pressure, because the molecules move faster, so they collide with the container walls more often and with more force.
- Pressure and force A gas exerts a force at right angles to the walls of its container. Pressure is the total force per unit area exerted by the molecules colliding with the walls.
- Pressure and volume (physics only) For a fixed mass of gas at constant temperature, increasing the volume decreases the pressure: p V = constant. Calculate the change using p1 V1 = p2 V2 (pressure in Pa, volume in m^3).
- Explaining pV = constant (physics only) If the volume increases, the molecules are more spread out, so they hit the walls less often, so the force per unit area is smaller.
- Doing work on a gas (physics only, Higher tier only) Work is the transfer of energy by a force. Doing work on a gas, such as compressing it in a bicycle pump, increases its internal energy and can cause an increase in its temperature.
Common mistakes in 4.3.3 Particle Model and Pressure
- Saying molecules collide with each other to create pressure. Pressure comes from collisions of molecules with the walls of the container.
- Saying the molecules hit the walls 'harder' without also saying 'more often'. Full explanations of temperature rises usually need both.
- Using p V = constant when the temperature changes. It only applies to a fixed mass of gas at constant temperature.
- Saying gas molecules get bigger when heated. The molecules move faster; their size does not change.
Try three 4.3.3 Particle Model and Pressure exam-style questions
1. Explain why the pressure of a gas in a sealed container increases when it is heated. (3 marks)
Show the mark scheme answer
Molecules gain kinetic energy and move faster; they collide with the container walls more frequently; and with greater force, so force per unit area (pressure) increases.
2. Physics only: A gas has a volume of 0.030 m^3 at a pressure of 100 000 Pa. It is compressed at constant temperature to 0.020 m^3. Calculate the new pressure. (3 marks)
Show the mark scheme answer
p1 V1 = p2 V2; 100 000 x 0.030 = p2 x 0.020; p2 = 150 000 Pa.
3. Physics only, Higher tier: Explain why the air in a bicycle pump gets warmer when the pump is pushed in quickly. (3 marks)
Show the mark scheme answer
Work is done on the gas by the force pushing the piston; this transfers energy to the gas, increasing its internal energy; so the average kinetic energy of the molecules and the temperature increase.
4.3.3 Particle Model and Pressure FAQs
What does AQA GCSE Physics 4.3.3 Particle model and pressure cover?
It covers particle motion in gases, how temperature affects gas pressure, pressure and volume at constant temperature, and how doing work on a gas raises its temperature.
Which parts of 4.3.3 are physics only?
Pressure in gases (p V = constant) is physics only, and increasing the pressure of a gas by doing work on it is physics only and Higher tier only.
What equation do I need for gas pressure?
p V = constant for a fixed mass of gas at constant temperature, which is on the equation sheet. Use p1 V1 = p2 V2 to find a new pressure or volume.
