| A | B |
|---|
| Law of conservation of energy | energy is never created or destroyed |
| bacteria | the simplest things that carry out all basic life activities |
| physical properties | a characteristic of a substance that can be observed without changing the substance |
| chemical property | characteristic that describes how a substance changes to a different substance |
| proton | tiny positive particle in the nucleus |
| neutron | a tiny particle with no charge that is in the nucleus |
| electron | a tiny negative particle that surrounds the nucleus |
| isotope | an atom with the same number of protons and electrons and a different number of neutrons |
| chemical formula | an equation that tells the number and types of atoms in a reaction |
| ionic bond | a bond formed when an atom or molecule gains or loses one electron |
| covalent bond | a bond resulting from the sharing of electrons |
| reactants | a substance that is changed in a chemical reaction |
| products | a substance that is made in a chemical reaction |
| bonds | what holds two atoms together, can be ionic or covalent |
| compounds | two or more elements combined |
| atom | smallest unit of matter |
| element | matter made of one type of atom |
