| Term | Definition |
| Matter | Anything that has mass and takes up space. |
| Mass | Describes the amount of matter in an object. |
| Weight | A measure of the gravitational force on an object. |
| Volume | The amount of space that an object takes up, or occupies. |
| Density | A measure of the amount of mass that is in a given volume. |
| Physical property | A characteristic of a substance that can be observed and measured without changing the identity of the substance. |
| Chemical property | Describes the substance's ability to change into a new substance with different properties. |
| Physical change | A change that affects one or more physical properties of a substance. |
| Chemical change | Occurs when one or more substances changes into entirely new substances with different properties. |
| Law of conservation of mass | States that in ordinary chemical and physical changes, mass is not created or destroyed but is only transformed into different substances. |
| Atom | The smallest unit of an element that maintains the properties of that element. |
| Element | Made up of one or more of the same kind of atom chemically combined. |
| Compound | Made up of different kinds of atoms chemically combined. |
| Mixture | Contains a variety of elements and compounds that are not chemically combined with each other. |
| Pure substance | Elements and compounds. |
| Heterogeneous | one that does not have a uniform composition. |
| Homogeneous | One that has a uniform composition. |
| Solid | Has a definite volume and shape. |
| Liquid | Has a definite volume but not a definite shape |
| Gas | Does not have a definite volume or shape. |
| Freezing | The change in state in which a liquid becomes a solid. |
| Melting | The change in state in which a solid becomes a liquid. |
| Evaporation | The change in state in which a liquid becomes a gas |
| Boiling | The rapid change from a liquid to a gas |
| Condensation | The change of a gas to a liquid. |
| Sublimation | The change of a solid state directly into a gas |
| Deposition | The change in state from a gas directly to a solid. |
