This activity covers the following National Curriculum areas:

Key Stage 3 Science Sc4 Physical Processes: Energy resources and energy transfer: conservation of energy

Key Stage 4 Science Sc4 Physical Processes: Energy Resources and energy transfer: work, power and energy

1. Simple friction to generate heat and even ignite wood.

How hot does a match have to be before it ignites? Can we measure this?

Slowly raise the temperature of a match and monitor the temperature until it ignites.

2. Experiment to find the mechanical equivalent of heat in a simpler way.

Take a tube about one or two (or h) metres long and put in about half a kilogram (or mkg) of lead shot.

Allow both the lead shot and the water to come to room temperature and then keep the water in a thermos flask (use a thermos carefully).

Invert the tube n times. Each time it is inverted the lead shot falls through a height h and the loss of energy is equal to the total loss of potential energy or the work done (nmgh).

Quickly put the shot into the water and measure the rise in temperature. Remember that the experiment is rather an approximate one, so we are justified in ignoring the thermal capacity of the containers.

Let the specific heat capacity of lead be C, the initial and final temperatures of the water be t_i and t_f and the temperature of the lead after falling through the height nh be t.

Therefore nmgh = JCm(t - t_i)

To calculate the temperature of the lead t, we say that:

Cm (t - t_i) = M (t_f - t_i) where M is the thermal capacity of the water.

This experiment is reminiscent of a well-known story about Joule. It is said that while on his honeymoon he tried to measure the temperature rise experienced by water as it fell from the top of a waterfall to the bottom. There is no record of his wife's comments on this behaviour!

3. Joule's experiments showed the equivalence of heat and other forms of energy, so perhaps it is worth reminding ourselves of a simple experiment involving electrical heating.

We measure the current and voltage of the heater and also the temperature rise and look at the equivalence of the heat energy and the electrical energy.