Thermal chemistry is the study of matter and energy associated with chemical reactions or physical changes. Energy itself is just the capacity to do work or to produce heat. Now when we talk about energy, realize that there are different types of energy, but in this chapter, we're only going to focus on a selected few. Now when we take a look at the big picture, energy itself, we can say here that it can be broken down initially into either the position of atoms or the motion of atoms. When we're talking about the position of atoms, this is just simply our potential energy, our energy of position. And then if we're talking about the movement or motion of atoms, this is connected to kinetic energy. Now both potential energy and kinetic energy can be further broken down into other types of energy. Potential energy, we can connect it to another one which deals with the chemical bonds of atoms. This is just simply chemical energy. And then kinetic energy can be broken down further into energy associated, with temperature generated by the motion of atoms. So this would be called thermal energy. So just remember, energy is just the capacity to work and to produce heat. And when we're talking about energy in this chapter, we're mainly concerned with these different types of energy forms. Now, of course, there are other types of energy that exist. We'll go into those in later chapters, but for now, just remember these particular four.