Chemical Reactions - Key terms





ACID-BASE REACTION:

A chemical reaction in which an acid is mixed with a base, resulting in the formation of water along with a salt.

AQUEOUS SOLUTIONS:

A mixture of water and any substance that is solvent in it.

BALANCED EQUATION:

A chemical equation in which the numbers of atoms in the reactants and those in the product areequal. In the course of balancing an equation, coefficients may need to be applied to one or more of the chemical species involved; however, the actual formulas of the species cannot be changed.

CATALYST:

A substance that speeds upa chemical reaction without participating in it either as a reactant or product. Catalysts are thus not consumed in the reaction.

CHEMICAL EQUATION:

A representation of a chemical reaction in which the chemical symbols on the left stand for the reactants, and those on the right for the product or products. On paper, a chemical equation looks much like a mathematical one; however, instead of an equals sign, a chemical equation uses an arrow to show the direction of the reaction.

CHEMICAL KINETICS:

the study of the rate at which chemical reactions occur.

CHEMICAL REACTION:

A process whereby the chemical properties of a substance are changed by a rearrangement of the atoms in the substance.

CHEMICAL SPECIES:

A generic term used for any substance studied in chemistry—whether it be an element, compound, mixture, atom, molecule, ion, and so forth.

CHEMICAL THERMODYNAMICS:

The study of the amounts of heat and other forms of energy associated with chemical reactions.

COEFFICIENT:

A number used to indicate the presence of more than one unit—typically, more than one molecule—of a chemical species in a chemical equation. For instance, 2H 2 O indicates two water molecules. (Note that 1 is never used as a coefficient.)

COLLISION MODEL:

The theory that chemical reactions are the result of collisions between molecules that are strong enough to break bonds in the reactants, resulting in a rearrangement of atoms to form a product or products.

DECOMPOSITION REACTION:

A chemical reaction in which a compound is broken down into simpler compounds, or even into elements. This is the opposite of a synthesis or combination reaction.

DOUBLE-DISPLACEMENT REACTION:

A chemical reaction in which the partners in two compounds changeplaces. This can be symbolized as AB + CD →AD + CB. Compare single-displacement reaction.

ENDOTHERMIC:

A term describing a chemical reaction in which heat is absorbed or consumed.

EXOTHERMIC:

A term describing a chemical reaction in which heat is produced.

HETEROGENEOUS:

A term describing a chemical reaction in which the reactants are in different phases of matter (liquid, solid, or gas), or one in which the product is in a different phase from that of the reactants.

HOMOGENEOUS:

A term describing a chemical reaction in which the reactants and the product are all in the same phase of matter (liquid, solid, or gas).

OXIDATION-REDUCTION REACTION:

A chemical reaction involving the transfer of electrons.

PRECIPITATION REACTION:

A chemical reaction in which a solid isformed.

PRODUCT:

The substance or substances that result from a chemical reaction.

REACTANT:

A substance that interacts with another substance in a chemical reaction, resulting in the formation of aproduct.

SINGLE-DISPLACEMENT REACTION:

A chemical reaction in which an element reacts with a compound, and one of the elements in the compound is released as a free element. This can be represented symbolically as A + BC →B + AC. Compare double-displacement reaction.

STOICHIOMETRY:

The study of the relationships among the amounts of reactants and products in a chemical reaction. Producing a balanced equation requires application of stoichiometry (pronounced "stoy-kee-AH-muh-tree").

SYNTHESIS OR COMBINATIONREACTION:

A chemical reaction in which a compound is formed from simpler materials—either elements or simple compounds. It is the opposite of a decomposition reaction.

UNBALANCED EQUATION:

A chemical equation in which the sum of atoms in the product or products does not equal the sum of atoms in the reactants. Initial observations of a chemical reaction usually produce an unbalanced equation, which needs to be analyzed and corrected (by the use of coefficients) to yield a balancedequation.