| Word | Meaning |
| physical change | a change with no new substance, which can be reversed |
| chemical change | a change that makes a new substance and cannot be reversed |
| chemical reaction | the process in which atoms join, split and swap to make new substances |
| chemical equation | a chemical reaction written in the form of an equation |
| reactants | the substances that take part, written on the left |
| products | the substances formed, written on the right |
| word equation | an equation written with the names of the substances |
| formula equation | an equation written with symbols and formulae |
| balanced chemical equation | a formula equation with equal atom counts on both sides |
| joining | separate atoms coming together |
| breaking apart | joined atoms coming loose |
| exchange | atoms swapping places with one another |