#separator:tab #html:false #tags column:4 Atom The smallest unit of an element that still has its properties chem-basic-terms Molecule Two or more atoms joined together chem-basic-terms Element A pure substance made of only one kind of atom chem-basic-terms Compound A substance made of two or more elements chemically joined chem-basic-terms Mixture Two or more substances together but not chemically joined chem-basic-terms Proton Positive particle in the nucleus chem-basic-terms Neutron Particle with no charge in the nucleus chem-basic-terms Electron Tiny negative particle that moves around the nucleus chem-basic-terms Nucleus The center of an atom, holding protons and neutrons chem-basic-terms Ion An atom or group of atoms with an electric charge chem-basic-terms Cation A positive ion chem-basic-terms Anion A negative ion chem-basic-terms Ionic bond A bond formed when electrons move from one atom to another chem-basic-terms Covalent bond A bond formed when atoms share electrons chem-basic-terms Metallic bond A bond in which electrons flow freely among metal atoms chem-basic-terms Chemical formula Symbols and numbers showing what atoms make up a substance chem-basic-terms Chemical reaction A process in which substances change into new substances chem-basic-terms Reactant A starting substance in a chemical reaction chem-basic-terms Product A substance made by a chemical reaction chem-basic-terms Chemical equation A way to show a reaction using formulas chem-basic-terms Law of conservation of mass Matter is not created or destroyed in a chemical reaction chem-basic-terms Catalyst A substance that speeds up a reaction without being used up chem-basic-terms Enzyme A biological catalyst, made of protein chem-basic-terms Solution A mixture that is the same all the way through chem-basic-terms Solute The substance that is dissolved chem-basic-terms Solvent The substance that does the dissolving chem-basic-terms Solubility How much of a substance can dissolve in a solvent chem-basic-terms Concentration How much solute is in a certain amount of solution chem-basic-terms Saturated solution One that cannot dissolve any more solute chem-basic-terms Suspension A mixture with particles that settle out if left alone chem-basic-terms Colloid A mixture with tiny particles that stay spread out, like milk chem-basic-terms Density How much mass is in a given volume chem-basic-terms Mass The amount of matter in an object chem-basic-terms Volume The amount of space something takes up chem-basic-terms Physical change A change in form that does not make a new substance chem-basic-terms Chemical change A change that makes new substances chem-basic-terms Physical property A trait you can observe without changing the substance, like color chem-basic-terms Chemical property How a substance can change into another, like flammability chem-basic-terms Exothermic reaction A reaction that gives off heat chem-basic-terms Endothermic reaction A reaction that takes in heat chem-basic-terms Oxidation A reaction in which a substance loses electrons or combines with oxygen chem-basic-terms Reduction A reaction in which a substance gains electrons chem-basic-terms Precipitate A solid that forms from a liquid solution during a reaction chem-basic-terms Distillation Separating liquids by boiling and condensing them chem-basic-terms Filtration Separating solids from liquids using a filter chem-basic-terms Evaporation A liquid changing to a gas at its surface chem-basic-terms Condensation A gas changing into a liquid chem-basic-terms Mole A unit for counting atoms: 6.02 x 10^23 particles chem-basic-terms Avogadro's number 6.02 x 10^23, the number of particles in one mole chem-basic-terms Molar mass The mass of one mole of a substance chem-basic-terms Valence electron An electron in the outer shell that takes part in bonding chem-basic-terms Atomic number Number of protons in an atom chem-basic-terms Mass number Protons plus neutrons in an atom chem-basic-terms Isotope Atoms of one element with different numbers of neutrons chem-basic-terms Radioactivity The giving off of energy and particles by unstable atoms chem-basic-terms Half-life Time it takes half of a radioactive sample to decay chem-basic-terms Polymer A large molecule made of many repeating units chem-basic-terms Organic compound A compound built on carbon, usually with hydrogen chem-basic-terms Allotrope One of different forms of the same element, like diamond and graphite chem-basic-terms Alloy A mixture of metals, such as brass or steel chem-basic-terms Corrosion The slow wearing away of metal by chemical reaction chem-basic-terms Combustion Burning: a fast reaction of a fuel with oxygen chem-basic-terms Synthesis reaction Two or more substances combine to make one product chem-basic-terms Decomposition reaction One compound breaks down into simpler substances chem-basic-terms Electrolysis Using electricity to split a compound chem-basic-terms Inert Not reacting easily with other substances chem-basic-terms Reactivity How easily a substance takes part in chemical reactions chem-basic-terms Malleable Able to be hammered into thin sheets chem-basic-terms Ductile Able to be pulled into wire chem-basic-terms Conductor A material that lets heat or electricity flow easily chem-basic-terms Insulator A material that does not let heat or electricity flow easily chem-basic-terms Electronegativity How strongly an atom pulls on shared electrons chem-basic-terms Periodic law Element properties repeat in a pattern as atomic number goes up chem-basic-terms