| A | B |
|---|
| Matter | anything that occupies space and has mass |
| Element | pure substance that cannot be broken down into other substances by chemical or physical means |
| Trace element | element critical to health that makes up less than 0.01 percent of body mass |
| Compound | substance containing two or more elements chemically combined in a fixed ratio |
| Atom | smallest particle of an element |
| Subatomic Particle | any of the three particles that make up an atom – proton |
| Proton | subatomic particle with a single unit of positive electric charge (+) |
| Electron | subatomic particle with a single unit of negative electric charge (-) |
| Neutron | subatomic particle that has no charge (is electrically neutral) |
| Nucleus | in an atom |
| Atomic number | number of protons in an atom's nucleus; is unique for each element |
| Isotope | one of several forms of an element |
| Radioactive isotope | isotope in which the nucleus decays (breaks down) over time |
| Ionic bond | chemical bond that occurs when an atom transfers an electron to another atom |
| Ion | atom that has become electrically charged as a result of gaining or losing an electron |
| Covalent bond | chemical bond that forms when two atoms share electrons |
| Molecule | two or more atoms held together by covalent bonds |
| Chemical reaction | breaking of old and formation of new chemical bonds that result in new substances |
| Reactant | starting material for a chemical reaction |
| Product | material created as a result of a chemical reaction |
| Polar molecule | molecule in which opposite ends have opposite electric charges |
| Hydrogen bond | bond created by the weak attraction of a slightly positive hydrogen atom to a slightly negative portion of another molecule |
| Cohesion | tendency of molecules of the same kind to stick to one another |
| Adhesion | attraction between unlike molecules |
| Thermal energy | total amount of energy associated with the random movement of atoms and molecules in a sample of matter |
| Temperature | measure of the average energy of random motion of particles in a substance |
| Solution | uniform mixture of two or more substances |
| Solvent | substance in a solution that dissolves the other substance and is present in the greater amount |
| Solute | substance in a solution that is dissolved and is present in a lesser amount |
| Aqueous solution | solution in which water is the solvent |
| Acid | compound that donates H+ ions to an aqueous solution and measures less than 7 on the pH scale |
| Base | compound that removes H+ ions from an aqueous solution and that measures more than 7 on the pH scale |
| pH scale | a range of numbers used to describe how acidic or basic a solution is; ranges from 0 (most acidic) to 14 (most basic) |
| buffer | substance that maintains a fairly constant pH in a solution by accepting H+ ions when their levels rise and donating H+ ions when their levels fall |
