Latent heat of melting describes the amount of heat required to melt a solid.

How does the total energy graph of melting compare to the one for condensation?

1. In the first model below, investigate adding heat to the system.
2. Add energy to the system by clicking on the Start adding heat button below the model window.
3. Observe the Kinetic and Potential energy bars. How does the kinetic energy change as the potential energy increases?
4. How does the graph of the total energy in the system change as heat is added?

1. In the second model below, investigate removing heat to the system.
2. Remove energy from the system by clicking on the Start cooling button below the model window.
3. Observe the Kinetic and Potential energy bars. How does the kinetic energy change as the potential energy decreases?
4. How does the graph of the total energy in the system change as heat is removed?

1. In the above models, the energy added to the system is absorbed by the atoms and used to break the interatomic interactions so that they can leave the condensed state. The kinetic energy doesn’t increase as the potential energy increases. Why?
2. One thing you would notice is that the Temperature-Total energy graph has fluctuations. Why do you think this is so?

When you boil something you constantly add heat. However, if you measure the temperature of the boiling water it stays the same. Where does this heat energy go if it doesn’t cause the temperature to increase?

Below is a bunch of Helium atoms, which have been cooled and condensed. Slowly heat the Helium by pressing the heat button for a short amount of time (a single click). This will add a small amount of KE to each Helium atom. If you watch carefully, you will see an interesting pattern. At first the average kinetic energy (temperature) will increase, then the temperature will stay at about the same level for a while, and then, if you keep adding heat, the temperature will start to increase again. Why does this happen?