Hammering lead to warm it up
Using kinetic energy to heat different components.
Apparatus and materials
Blunt drill bit
Piece of metal and G-clamp
Piece of sheet lead
Hammer and hardwood 'anvil'
Iron wire to hold piping
Health & Safety and Technical notes
a Clamp the metal over a scrap of softwood to the bench.
Bore a hole in the piece of metal with the blunt drill, then pass the drill bit round so that it can be felt.
b Push the stiff iron wire through the lead piping and bend the end so as to hold the lead. Hammer the lead violently so that its temperature rises. A piece of lead sheet may be used instead of the piping, as shown in the diagram.
c Ask students to push in the piston of a bicycle pump quickly whilst holding a finger on the outlet so that they can feel the heating.
1 In all these demonstrations the components warm up. When the action stops, all the kinetic energy of the moving parts has been transferred to the components, so increasing their thermal energy.
2 The bicycle pump warms up because the kinetic energy and hence the speed of the air molecules inside the cylinder has increased. Momentum is transferred from the moving piston to the air molecules in the same way as hitting a ball with a moving bat transfers momentum.
3 There are occasions when energy is transferred to a body but its temperature does not rise. If a beaker of crushed ice is melted with a Bunsen flame, the resulting slush remains at freezing point. In this case the heating increases potential energy in the force-fields of the molecular structure, as the molecules are pulled apart against the forces of mutual attraction that hold them in a solid crystal. The energy needed to do this is known as 'latent heat'. (The term is too well established to think of calling it anything else - but beware of the word 'heat'.)
This experiment was safety-checked in November 2005