Section 1: What is energy?

Definition: Energy is the capacity to do work. Energy is not a “thing”. Something has energy when it can achieve something, for example move, glow, make a sound.

Sources of Energy We get our ability to do things from our food. Our food is our source of energy. A fire gets its ability to do something (that is, heat other things up or burn things) from the wood. The wood is the source of the energy. Ultimately, the Sun is the source of energy for everything on Earth. Plants make their food by photosynthesis. The energy they need comes from the Sun.

Forms of Energy The form of the energy is the way that the ability to do something is produced in an object. For example, an object which can affect other objects because of its movement is said to have kinetic energy. (Kinetic is a word from Greek which means movement) An object which can affect other objects because it gives off light is said to have light energy.

More Forms of Energy Some things can’t affect anything yet, but are storing up the ability to affect something. For example, food sitting on a table cannot do any work yet, but if you eat it, you will gain energy So we say food has potential energy.

Types of Potential Energy Chemical potential energy - Will be able to do something because of the chemicals it contains Gravitational potential energy - will be able to do something because it is above the ground and can fall Elastic potential energy - will be able to do something because it is wound up or stretched and will spring back when released.

Some Forms of Energy Mechanical Chemical potential Nuclear Sound Heat (thermal) Light Electrical Elastic potential