Pressure in gases
Teaching Guidance for 11-14
Pressure from particles
Wrong Track: How can there be pressure inside gases? They're too thin, they're not like water.
Right Lines: The air around us has a pressure just like water. This air pressure is due to the bombardment of air molecules. We don't notice air pressure until air is removed from one side of a surface (remove air from a Coke can and the air on the outside crushes the walls inwards).
Starting with liquids
Thinking about the learning
Pupils will readily accept the idea of pressure existing in liquids because it is a familiar phenomenon. However they may have problems in accepting that gases, such as the air around them, exert pressures.
Thinking about the teaching
Given that pupils are more familiar with pressure in liquids we recommend that you start with examples involving liquids and then move on to gases.