Internal Energy

Internal Energy

In GCSE, you probably did an experiment where you took some ice, heated it steadily with an electric heater and measured the temperature as time passed. You should have got these results:

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Even though you heated constantly, the temperature only rose sometimes. So where was the heat going when the temperature wasn't rising?

Answer: it was being used to change the state of the water.

Remember in the energy topic we said that the energy of an atom was made up of two components - Ek (kinetic energy) and Ep (potential energy). Well:

The Ek component relates to the temperature of the substance

The Ep component relates to the state of the substance.

So during times of increase of temperature (e.g. a, c and e from the graph) the heat energy supplied is going into the Ek component of the internal energy.

And during changes of state (e.g. b and d) it's going to Ep. Because Ek isn't changing during these times, the temperature remains the same.