Energy is a quantity that measures the ability to cause change in a physical system. Anything with energy can change itself or cause change in other objects or systems. Energy can cause changes in temperature, speed, position, momentum, pressure, or other physical variables. 

Energy Example

One joule

Energy can also cause change in materials, such as burning wood changing into ashes and smoke. The unit of measurement for energy is the joule (J). One joule is the energy needed to push with a force of one newton over a distance of one meter. In other words, the joule is an abbreviation for one newton multiplied by one meter.