AQA GCSE Physics (8463), Higher tier · Particle model of matter › Particle model and pressure
Practise Particle motion in gases. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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A sealed metal can contains air. The can is heated. The volume of the can does not change. What happens to the pressure of the air inside the can?
It increases.
State what causes the pressure of a gas on the walls of its container.
Collisions of the gas particles with the walls.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) Which statement describes the motion of the molecules in a gas? Tick (✓) one box.[1]
The molecules are not moving.
The molecules vibrate about fixed positions.
The molecules are in constant random motion.
The molecules all move in the same direction.
(b) Which quantity is related to the average kinetic energy of the molecules in a gas? Tick (✓) one box.[1]
Density
Mass
Temperature
Volume
(c) A sealed metal can contains air. The can is heated. The volume of the can does not change. What happens to the pressure of the air inside the can?[1]
(d) Aerosol cans contain gas under pressure. They carry the warning ‘Do not heat’. Suggest why.[1]
Show the answer and mark scheme
(a)Answer: The molecules are in constant random motion.
(b)Answer: Temperature
(c)Answer: It increases.
it increases
(d)Answer: Heating would increase the pressure of the gas, so the can could burst.
heating increases the pressure of the gas inside the can, so the can could burst / explode
Question 2Medium5 marks
A sealed glass flask contains air. The flask is put in a water bath and heated from 20 °C to 60 °C. The volume of the flask does not change.
(a) Explain why the pressure of the air in the flask increases. Your answer should refer to the motion of the air molecules.[3]
(b) A second sealed flask of air at 20 °C is cooled to 5 °C. Describe what happens to the motion of the air molecules and to the pressure of the air in this flask.[2]
Show the answer and mark scheme
(a)Answer: The molecules gain kinetic energy and move faster, so they hit the walls more often and with more force, increasing the force per unit area.
the (average) kinetic energy of the molecules increases / the molecules move faster (on average)
the molecules collide with the walls of the flask more often
the molecules exert a greater force on the walls in each collision
so the force on each unit area of the walls / the pressure increases
(b)Answer: The molecules move more slowly on average, so the pressure of the air decreases.
the molecules move more slowly (on average) / have a lower average kinetic energy
the pressure decreases
Question 3Hard6 marks
Explain, in terms of the motion of the gas particles, why the pressure of a fixed mass of gas in a sealed rigid container increases when its temperature increases.[6]
Show the answer and mark scheme
Answer: Higher temperature means faster-moving particles, which collide with the walls more often and with more force each time, increasing the total force and so the pressure on the fixed-area walls.
increasing the temperature increases the average kinetic energy of the gas particles
so the particles move faster, on average
the particles collide with the walls of the container more frequently
each collision also exerts a greater force on the wall, because the particles are moving faster
both effects (more frequent collisions and a greater force per collision) increase the total force on the walls
since the area of the container is fixed, this increase in force increases the pressure
Marked with levels of response: the full level descriptors are in the app.