Energy can take several forms — such as heat energy, light energy, electrical energy, and mechanical energy. But two general types of energy are especially important to chemists: kinetic energy and potential energy.
Energy is one of two components of the universe. Matter is the other component. Energy is the ability to do work.
Kinetic energy is energy of motion. A baseball flying through the air toward a batter has a large amount of kinetic energy. Ask anyone who’s ever been hit with a baseball, and they’re likely to agree!
Chemists sometimes study moving particles, especially gases, because the kinetic energy of these particles helps determine whether a particular reaction may take place. The reason is that collisions between particles and the transfer of energy cause chemical reactions to occur.
The kinetic energy of moving particles can be transferred from one particle to another. Have you ever shot pool? You transfer kinetic energy from your moving pool stick to the cue ball to (hopefully) the ball you’re aiming at.
Kinetic energy can be converted into other types of energy. In a hydroelectric dam, the kinetic energy of the falling water is converted into electrical energy. In fact, a scientific law — The Law of Conservation of Energy — states that in ordinary chemical reactions (or physical processes), energy is neither created nor destroyed but can be converted from one form to another.
Suppose you take a ball and throw it up into a tree where it gets stuck. You gave that ball kinetic energy — energy in motion — when you threw it. But where’s that energy now? It’s been converted into the other major category of energy — potential energy.
Potential energy is stored energy. Objects may have potential energy stored in terms of their position. That ball up in the tree has potential energy due to its height. If the ball were to fall, that potential energy would be converted to kinetic energy.
Potential energy due to position isn’t the only type of potential energy. In fact, chemists really aren’t all that interested in potential energy due to position. Chemists are far more interested in the energy stored (potential energy) in chemical bonds, which are the forces that hold atoms together in compounds.
It takes a lot of energy to run a human body. If there were no way to store the energy you extract from food, you’d have to eat all the time just to keep your body going. But humans can store energy in terms of chemical bonds. And then later, when we need that energy, our bodies can break those bonds and release it.
The same is true of the fuels we commonly use to heat our homes and run our automobiles. Energy is stored in these fuels — gasoline, for example — and is released when chemical reactions take place.