The law of conservation of energy states that in a closed system the total amount of energy is conserved and does not change. This means that energy may change from one form to another, but that the total amount of energy in the closed system remains constant.
Energy is defined as the ability to do work. There are different types of energy including kinetic energy, potential energy, chemical energy, electrical energy and thermal energy. Energy has the ability to convert from one form to another.
Kinetic energy is the energy of motion and is a product of both the mass and the velocity of an object. This is in contrast to potential energy, which is stored energy conserved at some reference point. A compressed spring has potential energy, which escapes when the spring is released. Chemical energy is energy stored between molecular bonds. This energy may be released when the molecule undergoes a chemical reaction.
Electrical energy is energy created by the existence of separate charges, such as positive and negative charges. This type of energy is found in batteries. Thermal energy is energy given off in the form of heat, which may occur due to friction. For example, when wood burns it converts potential energy in the wood into heat and light energy when it burns. As water and carbon dioxide dissipate from the wood, these molecules escape by means of kinetic energy.