A pressure cooker is a metal pan used to cook food. The lid locks onto the pan so that no gas can escape.
When the pressure cooker is heated, the pressure of the gas inside increases.
A student writes:
'When the gas is heated, the particles get bigger, so they hit the walls of the pan more often.'
Identify the mistake in the student's statement and write a correct explanation.
Explain why the lid of the pressure cooker must be locked onto the pan.
The pressure cooker has a safety valve. The valve opens and lets gas out if the pressure becomes too high.
Explain, in terms of particles, how opening the valve reduces the pressure inside the pan.
50 exam-style questions on OCR GCSE Physics 1.3 Pressure, covering 1.3.1 Molecular motion, temperature and gas pressure, 1.3.2 Gas pressure at constant volume, 1.3.3 Compressing and expanding gases, 1.3.4 Gas volume and pressure at constant temperature, 1.3.5 Doing work on a gas, 1.3.6 The Earth's atmosphere and atmospheric pressure, 1.3.7 Atmospheric pressure and height, 1.3.8 Floating and sinking, 1.3.9 Pressure in liquids and upthrust, and 1.3.10 Pressure differences with depth. Each one has a worked solution and a mark scheme showing where the marks go.