Biology In Focus Chapter 2


A substance that increases the hydrogen ion concentration of a solution


the clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds


A negatively charged ion


the smallest unit of matter that still retains the properties of an element

Atomic mass

The total mass of an atom, numerically equivalent to the mass in grams of one mole of the atom

Atomic number

The number of protons in the nucleus of an atom, unique for each element and designated by a subscript


a substance that reduces the hydrogen ion concentration of a solution


A solution that contains a weak acid and its corresponding base, a buffer minimizes changes in pH when acids or bases are added to the solution


The amount of heat energy required to raise the temperature of 1 g of water by 1°C; also the amount of heat energy that 1 g of water releases when it cools by 1°C

Capillary action

the movement of liquid along a surface of a solid caused by the attraction of molecules of the liquid to the molecules of the solid


A positively charged ion

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


the linking together of like molecules, often by hydrogen bonds


a substance consisting of two or more different elements combined in a fixed ratio

Covalent bond

A type of strong chemical bond in which two atoms share one or more pairs of valence electrons


the separation of ions that occurs when an ionic compound dissolves


a substance that breaks down into ions when dissolved in a solution


A subatomic particle that has a negative charge, has almost no mass, and is found outside of the nucleus


The attraction of a given atom for the electrons of a covalent bond


Any substance that cannot be broken down into any other substance by chemical reactions


The change of state from a liquid to a gas

Functional group

A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and involved in chemical reactions

Heat of vaporization

the quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state


An organic molecule consisting only of carbon and hydrogen

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 or in another region of the same molecule


Having an affinity for water


Having an aversion to water; tending to coalesce and form droplets in water


An atom or group of atoms 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


One of two or more compounds that have the same numbers of atoms of the same elements but have different structures and different properties


One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass

Mass number

The total number of protons and neutrons in an atom's nucleus


Anything that has mass and takes up space


two or more atoms held together by covalent bonds


A subatomic particle that has no charge and that is found in the nucleus of an atom

Noble gas

Elements that make up group 18 on the periodic table and have full octets so they are relatively unreactive

Nonpolar covalent bond

A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity


An atom's central core, containing protons and neutrons

Organic molecule

a chemical compound containing the element carbon

pH scale

a measure of the hydrogen ion concentration of a solution, ranging from 0 to 14

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


a material resulting from a chemical reaction


A subatomic particle that has a positive charge and that is found in the nucleus of an atom


A starting material in a chemical reaction


the dissolving agent of a solution

Specific heat capacity

The amount of heat that must be absorbed or lost for 1g or a substance to change its temperature by 1°C

Sphere of hydration

A chemical structure that surrounds a solute in a solution in which the solvent is water

Surface tension

A measure of how difficult it is to stretch or break the surface of a liquid

Valence shell

The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom

Van der Waals interactions

Weak attractions between molecules or parts of molecules that result from transient local partial charges.