| Term | Definition |
| physical change | a change that alters the form or appearance of a material but does not make the element into a new substance |
| Chemical change | A change in which one or more substances combined or break apart to form new substances |
| reactant | A substance that enters into a chemical reaction |
| product | A substance formed as a result of a chemical reaction |
| endothermic reaction | A reaction out of sorts energy |
| exothermic reaction | action that releases energy usually in the form of heat |
| Precipitate | A solid that forms from a solution during a chemical reaction |
| Chemical equation | A short easy way to show a chemical reaction using symbols |
| law of conservation of mass | The principles that the total amount of matter is neither created nor destroyed during any chemical or physical change |
| Open system | A system in which matter can enter from or escape to the surroundings |
| closed system | A system in which no matter is allowed to enter or leave |
| coefficent | A number in front of a chemical formula and equation that indicates how many molecules or Adams of each reactant and product involved in a reaction |
| replacement | and reaction in which one element replaces another in a compound or two elements in different compounds trade places |
| synthesis | A chemical reaction in which two or more simple substances combined to form a new more complex substance |
| decomposition | A chemical reaction that breaks down compounds into simpler products |
| activation energy | The minimum amount of energy needed to start a chemical reaction |
| concentration | The amount of one material in a certain volume of another material |
| enzyme | A type of protein that speeds up a chemical reaction in a living thing A biological catalyst that lowers the activation energy of reactions in cells |
| catalyst | and materials that increases the rate of reaction by lowering the activation energy |
| inhibitor | to material that decreases the rate of a reaction |
