| A | B |
|---|
| acid | A substance that increases the hydrogen ion concentration of a solution. |
| acid precipitation | Rain, snow, or fog that is more acidic than pH 5.6. |
| atom | The smallest unit of matter that retains the properties of an element. |
| atomic number | The number of protons in the nucleus of an atom, unique for each element and designated by a subscript to the left of the elemental symbol. |
| atomic weight | The total atomic mass, which is the mass in grams of one mole of the atom. |
| base | A substance that reduces the hydrogen ion concentration of a solution. |
| buffer | A substance that consists of acid and base forms in a solution and that minimizes changes in pH when extraneous acids or bases are added to the solution. |
| chemical bond | An attraction between two atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms; the bonded atoms gain complete outer electron shells. |
| chemical reaction | A process leading to chemical changes in matter; involves the making and/or breaking of chemical bonds. |
| cohesion | The binding together of like molecules, often by hydrogen bonds. |
| covalent bond | A type of strong chemical bond in which two atoms share one pair of valence electrons. |
| double covalent bond | A type of covalent bond in which two atoms share two pairs of electrons; symbolized by a pair of lines between the bonded atoms. |
| electron | A subatomic particle with a single negative charge; one or more electrons move around the nucleus of an atom. |
| electron shell | An energy level representing the distance of an electron from the nucleus of an atom. |
| electronegativity | The attraction of an atom for the electrons of a covalent bond. |
| element | Any substance that cannot be broken down to any other substance. |
| heat | The total amount of kinetic energy due to molecular motion in a body of matter. Heat is energy in its most random form. |
| hydrogen bond | A type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule. |
| ion | An atom that has gained or lost electrons, thus acquiring a charge. |
| ionic bond | A chemical bond resulting from the attraction between oppositely charged ions. |
| isotope | One of several atomic forms of an element, each containing a different number of neutrons and thus differing in atomic mass. |
| mass number | The sum of the number of protons and neutrons in an atom's nucleus. |
| matter | Anything that takes up space and has mass. |
| molecule | Two or more atoms held together by covalent bonds. |
| neutron | An electrically neutral particle (a particle having no electrical charge), found in the nucleus of an atom. |
| nonpolar covalent bond | A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity. |
| nucleus | (1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons. |
| pH scale | A measure of hydrogen ion concentration equal to -log [H+] and ranging in value from 0 to 14. |
| polar covalent bond | A type of covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive. |
| polar molecule | A molecule (such as water) with opposite charges on opposite sides. |
| product | An ending material in a chemical reaction. |
| proton | A subatomic particle with a single positive electrical charge, found in the nucleus of an atom. |
| radioactive isotope | An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy. |
| reactant | A starting material in a chemical reaction. |
| salt | salt |
| solute | A substance that is dissolved in a solution. |
| solution | A homogeneous, liquid mixture of two or more substances. |
| solvent | The dissolving agent of a solution. Water is the most versatile solvent known. |
| surface tension | A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules. |
| temperature | A measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules. |
| trace element | An element indispensable for life but required in extremely minute amounts. |
