Energy is all around us. It's the basis for life and it allows us to
do work. In fact, the simplest definition for energy is "the ability
to do work." Energy can exist in one of two types: potential or
kinetic. Kinetic energy is the energy of motion. Anytime an
object moves, it possesses kinetic energy. Kinetic energy comes
in a variety of forms: sound, light, heat, and electrical.
Potential energy is stored energy. The word potential means
"the ability to develop into something in the future." There are
many different forms of potential energy. Some forms are part of
our everyday lives, while other forms of potential
energy are less common.
One form of potential energy is gravitational
energy. Gravitational energy is the potential
energy that an object has because of its position
relative to a baseline or to the ground. Imagine a
child sitting at the top of a slide. Neither the child
nor the slide is moving, so there is no kinetic
energy at this point. But the moment the child
scoots forward onto the slope of the slide, she
begins to move down the slide. At the top of the
slide, she has a certain amount of potential energy.
Gravity pulls her down the slide to the ground. Her
gravitational energy decreases as she nears the
ground. A child at the top of a slide has greater gravitational
energy than a child at the bottom of the slide.
A second form of potential energy is elastic energy. A rubber
band is an example of elastic energy. An unstretched rubber
band contains no potential energy. The tighter you stretch the
rubber band, the more elastic energy it contains. When you
release the rubber band, that elastic energy can become kinetic
energy. Trampolines and bungee cords make use of elastic
energy. A hunter's bow works using elastic energy as well. When
the bowstring is released, the stored elastic energy is released
and transferred to the arrow as kinetic energy.
A third form of potential energy is chemical energy. Chemical
energy is the type of energy stored in the bonds of atoms and
molecules. Common fuels we use every day, such as petroleum,
natural gas, and coal, contain chemical energy. The hydrocarbon
molecules in these fuels have stored chemical energy. When we
burn these fuels, the energy is released. We use this released
energy to propel our cars, light and heat our homes,
and power our appliances. Another substance that
contains chemical energy is wood. When we burn
wood, we break the bonds of the molecules that make
up the wood. The stored chemical energy becomes
thermal energy, or heat.
Another form of potential energy is electrical
energy. Electrical energy is energy that comes from
charged particles. Electricity is a form of electrical
energy. A battery stores energy as chemical energy,
which it converts to electrical energy in a circuit. When
the battery is connected to a toy or appliance, an
electrical current is allowed to flow.
A final form of potential energy is nuclear energy. Nuclear
energy is stored in the nucleus of an atom. When the atom is
split in a reactor, large amounts of energy are released. Some
power plants utilize nuclear energy to produce electricity, but
splitting atoms isn't simple, and the process involves some risk.