is what we use to make things happen. Really, energy is the ability
to do work. There are different types of energy, like , sound,
electricity, and light. And energy can change from one kind to another.
For example, a car changes chemical energy stored as a fossil fuel
into heat energy, which runs the engine.
is what we do with energy. Work is when a force moves an object
over a distance. Work is when matter is changed into another form
or state. In other words, anytime we move something from one place
to another, we are doing work. (Taking a book off a shelf.) Anytime
an object is changing form, it is doing work. (A cell dividing into
two, pictured at right.)