A substance that can be separated into simpler substances (elements or other compounds) only by chemical reaction.
A mixture that is not uniform in composition; its components are readily distinguished.
Law of Conservation of Mass
Mass can be neither created nor destroyed in an ordinary chemical or physical process.
The zero point on the Kelvin temperature scale, equivalent to -273 ˚C; all molecular motion theoretically stops at this temperature.
Kelvin Temperature Scale (Kelvins, K)
The temperature scale in which the freezing point of water is 273 Kelvins and the boiling point is 373 Kelvins; 0 Kelvin is absolute zero.
Expression of number in the form of N x 10n, where N is equal 1or less than 10 and n is an integer.
A technique of problem-solving that uses the units that are part of a measurement to help solve the problem.
Atoms of the same element that have the same atomic number but different atomic masses due to different numbers of neutrons.
The lowest whole-number ratio of ions in ionic compounds; in magnesium chloride, the ratio of magnesium ions to chloride ions is 1:2 and the formula unit is MgCl2.
A vertical column of elements in the periodic table; the constituent elements of a group have similar chemical and physical properties.
An atom or group of atoms that has a positive or negative charge; cations are ions with positive charges, and anions are ions with a negative charge.
A chemical formula that shows the actual number and kinds of atoms present in a molecule of a compound.
An element that belongs to an A group in the periodic table; they are called representative elements because they illustrate the entire range of chemical properties.
The number of representative particles contained in one mole of a substance; equal to 6.02 x 1023 particles.
A formula with the lowest whole-number ratio of elements in a compound; the empirical formula of hydrogen peroxide, H2O2, is HO.
(mol) The amount of a substance that contains 6.02 x 1023 representative of that substance; a gram of formula mass of any substance.
Standard Temperature and Pressure (STP)
The conditions under which the volume of a gas is usually measured; standard temperature is 0˚C and standard pressure is 1 atmosphere (atm).
A chemical reaction change in which two or more substances react to form a single new substance; also caked a synthesis reaction.
Net Ionic Equation
An equation for a reaction in solution showing only those particles directly involved in the chemical change.
Any reactant that is used up first in a chemical reaction; it determines the amount of product that can be formed in the reaction.
The ratio of the actual yield to the theoretical yield for a chemical reaction expressed as a percentage; a measure of the efficiency of a reaction.
A molecular form of an element that exist in two or more different forms in the same physical state; oxygen, O2, and ozone, O3, are allotropes of the element oxygen.
A term used to describe a solid that lacks an ordered internal structure; denotes a random arrangement of atoms.
Substance in which the atoms, ions, or molecules are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice.
Standard Atmosphere (ATM)
A unit of pressure; it is the pressure required to support 760 mm of mercury in a mercury barometer at 25 C; this is the average atmospheric pressure at sea level.