Convection is a means of heat transfer that involves fluids, such as liquids or gasses. The process of convection is responsible for air and water currents as in the illustration. As the temperature of fluids increases their molecular motion increases, therefore as fluids warm their density decreases. A classroom demonstration of convection involves placing a small covered container filled with warm water to which food coloring has been added into a large container of cold water.

Materials will have different energies associated with the electrons inside them. this is related to how strongly bound they are by their work function. if we sandwich a material with a very low energy between two materials with a high energy, we create a trap for an electron. if this trap is very narrow in one direction in comparison to the others, this is approximately a 1-dimensional box that confines the electron. what is the lowest energy of an electron in the box if the thinnest direction across the materials is 4.81 nm?