atom
smallest basic unit of matter
element
substance made of only one type of atom that cannot be broken down by chemical means
compound
substance made of atoms of different elements that are bonded together in a particular ratio
ion
atom that has gained or lost one or more electrons
ionic bond
chemical bond formed through the electrical force between oppositely charged ions
covalent bond
chemical bond formed 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 (H+) when dissolved in a solution
base
compound that accepts a proton (H+) when dissolved in a solution
pH
measurement of acidity; related to free hydrogen ion concentration in a 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 often bonded to glycerol in a lipid
protein
polymer composed of amino acids linked by peptide bonds; folds in to 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 nucleotides; 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 between 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