Download Molecule: two or more atoms held together by

Chapter Two Vocabulary
2.1
Atom: smallest basic unit of matter
Element: substance made up of only one type of atom that cannot be broken down
by physical means
Compound: substance made of atoms of different atoms 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
2.2
Hydrogen bond: attraction between a slightly positive hydrogen atom and a
slightly negative atom
Cohesion: attraction between molecules of the same 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 solution
2.3
Monomer: molecular subunit of a polymer
Polymer: large, carbon-based molecule formed by monomers
Carbohydrate: molecule composed of carbon, hydrogen, 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 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 nucleotides; the genetic material of organisms
2.4
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
2.5
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