Internal energy: Practice Questions

Which of the following best describes the internal energy of a substance?

When a pure solid substance is at its melting point and is being heated, the temperature remains constant. What happens to the internal energy of the substance during this process?

A \(2.0\text{ kW}\) electric kettle contains \(1.0\text{ kg}\) of water already at its boiling point of \(100\text{ }^\circ\text{C}\). How much time is required to boil away exactly \(20\%\) of the water? (The specific latent heat of vaporisation of water is \(2.26 \times 10^6\text{ J/kg}\)).

The diagram shows the cooling curve of a pure substance as it cools from a liquid to a solid. In which section of the graph is the internal potential energy of the substance decreasing while the average kinetic energy of its particles remains constant?

A \(500\text{ g}\) block of ice at \(0\text{ }^\circ\text{C}\) is completely melted into water at \(0\text{ }^\circ\text{C}\). If the specific latent heat of fusion of ice is \(3.34 \times 10^5\text{ J/kg}\), how much thermal energy is absorbed by the ice?

Define internal energy of a substance in terms of the kinetic particle model of matter.