For the AP Chemistry exam, you need to know your vocabulary and definitions, but you also must know how to do math problems associated with these terms. As an example, take the term lattice energy. It’s important to know what this term means, but it’s also important to know how to apply it in calculations. For example, a question might ask you to calculate the lattice energy of a given crystal lattice composed of sodium and chlorine in a one-to-one ratio.