Like matter, energy can be classified in different ways. For example, energy can either be kinetic or potential.
Kinetic energy is energy of motion. Gases are made of molecules that have more kinetic energy than molecules in the solid phase of that substance. For example, water molecules in steam have greater kinetic energy than molecules in liquid water.
Potential energy is energy of position or stored energy. For example, there is quite a bit of energy stored in gasoline that can be used to power an automobile. Also, the potential energy of a gas is greater than the potential energy of a liquid because the individual molecules are positioned farther away from one another.
Another classification system for energy is based on its source. For example, energy can be electrical, light, chemical, or nuclear.
Two important energy laws are:
Conservation of Energy (also called the First Law of Thermodynamics). This law states that energy is neither created nor destroyed but is conserved. Energy, however, can be converted from one form to another. For example, plants convert light energy into the chemical energy of the molecules that make up the plant. V!hen animals eat the plant, the energy of the plant’s molecules is converted into heat energy.
Entropy (also called the Second Law of Thermodynamics). Entropy is measure of disorder. For example, whenever a system experiences a chemical reaction, something in the system increases in disorganization.
