1. Matter anything that has mass and takes up space

2. Atom the basic unit of matter: It is the smallest part of an element that has the chemical properties of that element. It can not be broken down by a chemical change.

3. Electron a negatively charge particle found outside the nucleus in a region called the electron cloud.

4. Proton the positively charged particle found in the nucleus of an atom.

5. Neutron a particle in the nucleus that has is neutral (no charge). It has the same mass as proton.

6. Nucleus the center of the atom containing the protons & neutrons.

7. Element a type of matter made of only one type of atom that have the identical number of protons in their nucleus

8. Compound A type of matter made up of elements that are chemically combined to form a new material with different properties from the original elements. The elements can not be separated by physical means.

9. Mixture A type of matter made up of two or more substances that are not chemically combined.

10. Atomic Mass or Weight number of protons & neutrons found in the nucleus of an atom

11. Atomic Number the number of protons in the nucleus

12. Physical Properties the characteristics that can be observed without chemically changing the substance.

13. Chemical Properties the characteristic that describes a how a substance will react with another substance, such as exploding when exposed to oxygen.

14. Physical Change This occurs when the physical properties of a substances changes, but no new substance is formed. Examples = evaporating, melting, freezing, sublimating.

15. Chemical Change This occurs when a chemical reaction takes place. The atoms are rearranged to form new substances with new physical and chemical properties.

16. Density The amount of matter (mass) in a given amount of space (volume). It is calculated by dividing mass by volume.

17. Boiling Point a physical property that identifies the temperature at which a liquid changes to a gas.

18. Melting Point a physical property that identifies the temperature at which a solid changes to a liquid. This is the same temperature as the freezing point, in which a liquid changes to a solid.

19. Law of Conservation of Matter Matter (mass) is not created nor destroyed in an ordinary chemical reaction.

20. State or Phase of Matter a physical property that describes matter as a solid, liquid, or gas. Matter changes states when either heat is added or taken away.