Warming up a gas by speeding up its particles
Apparatus and materials
Metal-bodied bicycle pump
Thermocolour film, cut to suitable size
Health & Safety and Technical notes
Thermocolour film is available from Mindsets under the name "thermocolour sheet".
ALTERNATIVE method: a video demonstrating the use of a fire piston is available at the National STEM Centre eLibrary. Air rapidly compressed in a piston ignites small piece of cotton wool.
a Fully extend the pump and block the hole at the bottom with a close-fitting bolt and PTFE tape. Attach the thermocolour film to the sides of the cylinder near the bolt.
b Make sure that the bicycle pump is cool. The temperature should be at the bottom of the range that the film will indicate.
c Fully extend the pump and squash the air up rather suddenly with one good push. Leave the piston at the position of maximum compression.
d Watch for the temperature rise of the cylinder, as shown by the thermocolour film attached to it.
1 This is another simple experiment that can be explained through kinetic theory. Ask students to explain what an increase in temperature of a gas suggests about the particles of the gas. Follow this up by asking for explanations of the increased particle speed. It may take some time before the class is happy that collisions with the approaching piston increase the velocities of the gas particles. (Consider the momentum changes of an air particle as it rebounds from the approaching piston.)
This experiment comes from AS/A2 Advancing Physics. It has been re-written for this website by Lawrence Herklots, King Edward VI School, Southampton.
This experiment was safety-checked in June 2004.