AP Bio vocab Ch. 2

282140170	element	a substance that cannot be broken down to other substances by ordinary chemical means
282140171	matter	anything that occupies space and has mass
282140172	compound	a substance consisting of two or more different elements combined in a fixed ratio
282140173	trace element	essential to human health, but only in small quantities
282140174	proton	a subatomic particle with a single positive electrical charge
282140175	electron	a subatomic particle with a single negative charge
282140176	neuron	a subatomic particle that is electrically neutral
282140177	nucleus	an atom's central core, where the protons and electrons are located
282140178	atomic number	the unique number of protons in the atom of a particular element
282140179	mass number	the sum of the number of protons and neurons in the nucleus
282140180	isotopes	have the same number of protons as the element, behave identically in chemical reactions, but have different numbers of neutrons
282140181	radioactive isotope	isotope whose nucleus decays spontaneously, giving off particles and energy
282142401	electron shells	certain energy levels at the nucleus that electrons move around
282142402	chemical bonds	attractions that hold atoms close together
282142403	covalent bond	the strongest kind of chemical bond, in which two atoms share one or more pairs of outer-shell electrons
282142404	molecule	made up of two or more atoms held together by covalent bonds
282142405	electronegativity	an atom's attraction for shared electrons
282142406	nonpolar covalent bonds	bonds in which electrons are shared equally between the atoms
282142407	polar covalent bonds	unequal sharing of electrons within a bond
282142408	polar molecule	molecule that has an unequal sharing distribution of charges
282142409	ionic bond	when opposite charges attract and hold together to form a bond
282147473	salt	a synonym for an ionic compound
282147474	hydrogen bond	a bond in which the positively charged region is always a hydrogen atom
282147475	chemical reaction	the breaking and making of chemical bonds, leading to changes in the composition of matter
282147476	reactants	the starting materials in a chemical reaction
282147477	product	the material resulting from a chemical reaction
282147478	cohesion	the tendency of molecules of the same kind to stick together
282147479	adhesion	the clinging of one substance to another
282147480	surface tension	a measure of how difficult it is to stretch or break the surface of a liquid
282147481	heat	the amount of energy associated with the movement of atoms and molecules in a body of matter
282147482	temperature	measures the intensity of heat or the average speed of molecules rather than the total amount of heat energy in a body of matter
282147483	evaporative cooling	when a substance evaporates, the surface of the liquid that remains behind cools down
282147484	solution	a liquid consisting of a uniform mixture of two or more substances
282147485	solvent	the dissolving agent
282147486	solute	the substance that is dissolved
282147487	aqueous solution	a solution in which water is the solvent
282147488	acid	a compound that donates hydrogen ions to solutions
282147489	base	a compound that accepts hydrogen ions and removes them from solutions
282147490	pH scale	describes how acidic or basic a solution is
282147491	buffers	substances that minimize changes in pH within solutions
282147492	acid precipitation	refers to rain, snow, or fog with a pH lower than 5.2
282147493	ocean acidification	CO2 dissolving in seawater lowers the ocean's pH because the CO2 reacts with carbonic acid