Term | Definition |
atom | smallest basic unit of matter |
element | substance made of only one type of atom that cannot be broken down by any chemical means |
compound | substance made of atoms of different elements that are bonded together |
ion | atom that has gained or loss one or more electrons |
covalent bond | chemical bond forms when two atoms share one or more pairs of electrons |
molecule | two or more atoms held together by covalent bonds; not necessarily a compound |
hydrogen bond | attraction between a slightly positive hydrogen atom and a slightly negative atom |
cohesion | attraction between molecules of the same substance |
adhesion | attraction between molecules of different substances |
solution | mixture that is consistent throughout; also called a homogeneous mixture |
solvent | substance in which solutes dissolve and that is present in greatest concentration in a solution |
solute | substance that dissolves in a solvent and is present at a lower concentration than the solvent |
acid | compound that donates a proton when dissolved in a solution |
base | compound that accepts a proton |
pH | measurement of acidity; related to free hydrogen ion concentration in solution |
monomer | molecular subunit of a polymer |
polymer | large, carbon-based molecule formed by monomers |
carbohydrate | molecule composed of carbon, hydrogen, and oxygen; includes sugars and starches |
lipid | nonpolar molecule composed of carbon, hydrogen, and oxygen; includes fats and oils |
fatty acid | hydrocarbon chain bonded to glycerol in a lipid |
protein | polymer composed of amino acids linked by peptide bonds; folds into a particular structure depending on bonds between amino acids |
amino acid | molecule that makes up proteins; composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur |
nucleic acid | polymer of nucleotidos; the genetic material of organisms |
chemical reaction | process by which substances change into different substances through the breaking and forming of chemical bonds |
reactant | substance that is changed by a chemical reaction |
product | substance formed by a chemical reaction |
bond energy | amount of energy needed to break a bond between two particular atoms; or the amount of energy released when a bond forms two particular atoms |
equilibrium | condition in which reactants and products of a chemical reaction are formed at the same rate |
activation energy | energy input necessary to initiate a chemical reaction |
exothermic | chemical reaction that yields a net release of energy in the form of heat |
endothermic | chemical reaction that requires a net input of energy |
catalyst | substance that decreases activation energy and increases reaction rate in a chemical reaction |
enzyme | protein that catalyzes chemical reactions for organisms |
substrate | reactant in a chemical reaction upon which an enzyme acts |