Pressure in liquids and gases
3 marks · NormalDescribe how you could demonstrate that gases exert pressure using simple apparatus in the laboratory.
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Use an inflated balloon or Magdeburg hemispheres. When the balloon is inflated, it expands as air pressure inside pushes out. With Magdeburg hemispheres, evacuating air creates a pressure difference and they stick together.
Also accept: Using airtight syringe, sealed can, or balloon as examples
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Marking points
B1 · 1 mark · Mentions apparatus such as a balloon or Magdeburg hemispheres
B2 · 1 mark · Explains expansion due to air pressure or sticking together due to pressure difference
B3 · 1 mark · Describes an observable effect (expansion or difficult to separate)
Worked solution
You could take a balloon and inflate it. The balloon expands, showing that air inside exerts pressure outward. Magdeburg hemispheres can be evacuated, showing how removing internal air causes atmospheric pressure to hold them together.