Suggest — 2 marks
A student investigates how pressure changes when a gas is compressed. They use a syringe filled with air at atmospheric pressure and push the plunger down, reducing the volume of gas inside without allowing any gas to escape.
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(a) Suggest why the pressure of the gas increases when the plunger is pushed down.
[1 mark]
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(b) Suggest how the rate of collisions between gas particles and the syringe walls changes as the volume decreases.
[1 mark]
Show mark scheme
- (a) The particles are forced closer together / the volume decreases
- (a) This causes more frequent collisions with the syringe walls
- (a) More collisions per unit time/area increases pressure
- (b) The rate of collisions increases
- (b) Because particles have less distance to travel between walls
- (b) Or: particles are in a smaller space / higher particle density
State — 5 marks
A student is investigating how gases behave in containers. They have a sealed syringe containing air at room temperature and atmospheric pressure. When they push the plunger in, they notice the air becomes harder to compress and the syringe feels warmer.
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(a) State what happens to the particles in the air when the plunger is pushed in.
[2 marks]
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(b) State how the pressure of the gas changes when the volume is reduced, and explain why in terms of particles.
[2 marks]
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(c) State one reason why the syringe feels warmer when the plunger is pushed in quickly.
[1 mark]
Show mark scheme
- (a) Particles are pushed/forced closer together (1 mark)
- (a) The distance between particles decreases / particles move closer (1 mark)
- (b) Pressure increases (1 mark)
- (b) Particles collide with the container walls more frequently / more collisions per unit time occur (1 mark)
- (c) Work done on the gas is converted to thermal energy / heat energy (1 mark)
Define — 2 marks
A deep-sea research vessel is studying ocean floor geology at a depth of 3000 metres. The submarine hull must withstand enormous pressure from the surrounding water. Engineers need to understand how pressure changes with depth to ensure the vessel remains safe.
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(a) Define pressure in terms of the particle model.
[1 mark]
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(b) Explain, using the particle model, why pressure increases as the submarine descends deeper into the ocean.
[1 mark]
Show mark scheme
- (a) Pressure is the force exerted per unit area by particles colliding with a surface / Pressure = Force ÷ Area (or equivalent statement showing force per unit area)
- (b) As depth increases, there is more water/mass above the submarine, so more particles are present / greater number of particles collide with the hull per unit time, resulting in increased pressure
Describe — 4 marks
A student is inflating a bicycle tyre using a hand pump. As they push the pump handle down, the air inside the pump becomes compressed before being forced into the tyre.
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(a) Describe how the particle model explains pressure in a gas.
[2 marks]
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(b) Describe what happens to the pressure of the air inside the pump as the pump handle is pushed down.
[1 mark]
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(c) Describe how increasing the temperature of a gas in a sealed container would affect the pressure, using the particle model.
[1 mark]
Show mark scheme
- (a) Gas particles move randomly in all directions / particles have random motion
- (a) Particles collide with the walls of the container / exert forces on the container walls
- (a) These collisions create pressure
- (b) The volume of air decreases / is compressed
- (b) Particles are forced closer together / particle density increases
- (b) More frequent collisions with walls occur / particles collide with walls more often
- (b) Pressure increases
- (c) Particles move faster / have increased kinetic energy
- (c) More frequent collisions with container walls occur
- (c) Greater force exerted in each collision / collisions are more forceful
- (c) Pressure increases
Suggest — 5 marks
A student investigates gas pressure in a sealed syringe. They push the plunger down, compressing the air inside to half its original volume at constant temperature. They observe that the pressure reading on a pressure gauge increases significantly.
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(a) Suggest why the pressure inside the syringe increases when the plunger is pushed down.
[2 marks]
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(b) The student then heats the sealed syringe gently. Suggest how this heating would affect the pressure inside the syringe and explain your answer in terms of particle behaviour.
[3 marks]
Show mark scheme
- (a) The volume decreases / particles are forced closer together
- (a) Particles collide with the walls more frequently / with greater force, causing pressure to increase
- (b) The pressure would increase
- (b) Heating gives particles more kinetic energy / particles move faster
- (b) This causes more frequent collisions with the container walls / collisions with greater force, increasing pressure
GCSE Perfect