Question Constellation Sign up for free AQA · GCSE · Combined Science · Higher
Coolant density, temperature and pressure
The compressor increases the density and temperature of the coolant vapour inside the pipe.
The compressor increases the density and temperature of the coolant vapour inside the pipe. Explain why the pressure in the pipe increases.
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Marking points
- 1 State that the coolant particles collide with the pipe walls more often, or that there are more collisions per second.
- 2 State that each collision produces a greater force on the pipe walls.
Full-mark answer
The higher density means the coolant particles collide with the pipe walls more often. The higher temperature means the particles move faster, so each collision exerts a greater force on the walls, increasing the pressure.
Why this answer loses marks
The density increases so the pressure increases.
This repeats the question information without explaining the particle-collision mechanism.