Chapter 2: The Chemical Basis of Life Flashcards
acid
A substance that increases the hydrogen ion concentration in a solution.
acid precipitation
Rain, snow, or fog with a pH below 5.6.
adhesion
The attraction between different kinds of molecules.
aqueous solution
A solution in which water is the solvent.
atom
The small unit of matter that retains the properties of an element.
atomic mass
The approximate total mass of an atom; also called atomic weight. Given as a whole number, the atomic mass approximately equals the mass number.
atomic number
The number of protons in each atom of a particular element.
base
A substance that decreases the hydrogen ion (H) concentration in a solution.
buffer
A chemical substance that resists changes in pH by accepting hydrogen ions from or donating hydrogen ions to solutions.
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
The making and breaking of chemical bonds, leading to changes in the composition of matter.
cohesion
The binding together of like molecules, often by hydrogen bonds.
compound
A substance containing two or more elements in a fixed ratio. For example, table salt (NaCl) consists of one atom of the element sodium (Na) for every atom of chlorine (Cl).
covalent bond
An attraction between atoms that share one or more pairs of outer-shell electrons; symbolized by a single line between the atoms.
electron
A subatomic particle with a single negative electrical 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 a given atom for the electrons of a covalent bond.
element
A substance that cannot be broken down to other substances by chemical means.
heat
Thermal energy; the amount of energy associated with the movement of the atoms and molecules in a body of matter. Heat is energy in its most random form.
hydrogen bond
A type of weak chemical bond formed when the partially positive hydrogen atom participating in a polar covalent bond in one molecule is attracted to the partially negative atom participating in a polar covalent bond in another molecule (or in another part of the same macromolecule).
ion
An atom that has gained or lost one or more electrons, thus acquiring a charge.
ionic bond
A chemical bond resulting from the attraction between oppositely charged ions.
isotope
A group of two or more atoms held together by covalent bonds.
molecule
A group of 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 covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
nucleus
(plural, nuclei) (1) An atom’s central core, containing protons and neutrons. (2) The genetic control center of a eukaryotic cell.
pH scale
A measure of the relative acidity of a solution, ranging in value from 0 (most acidic) to 14 (most basic). The letters pH stand for potential hydrogen and refer to the concentration of hydrogen ions (H).
polar covalent bond
A 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 containing polar covalent bonds.
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 whose nucleus decays spontaneously, giving off particles and energy.
reactant
A starting material in a chemical reaction.
salt
A compound resulting from the formation of ionic bonds; also called an ionic compound.
solute
A substance that is dissolved in a solution.
solution
A liquid consisting of a homogeneous mixture of two or more substances, consisting of a dissolving agent, called the solvent, and a substance that is dissolved, called the solute.
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 or speed of molecules.
trace element
An element that is essential for life but required in extremely minute amounts.
