Chem

concept 5 chemistry

Physical change

A change in a substance that does not alter its identity.

Chemical change

A change that transforms a substance into a different substance; a chemical reaction occurs.

Collision theory

Theory stating that reacting particles must collide with sufficient energy for a chemical reaction to occur.

Law of Conservation of Mass

Matter cannot be created or destroyed, only changing forms; total mass of reactants equals total mass of products.

Coefficients

Numbers in a chemical equation that represent the quantity of each substance involved.

Subscripts

Numbers in a chemical formula that indicate the number of atoms of an element in a molecule, which cannot be changed.

Reactants

Substances that start a chemical reaction.

Products

Substances formed as a result of a chemical reaction.

Aqueous (aq)

A state of matter indicating that a substance is dissolved in water.

Precipitate

An insoluble solid that forms from the reaction of two aqueous solutions.

Combustion

A chemical reaction in which a substance reacts with oxygen, often producing heat and light.

Synthesis reaction

A reaction in which two or more reactants combine to form a new compound.

Decomposition reaction

A reaction in which one reactant breaks down into two or more simpler products.

Single Replacement reaction

A reaction where one element replaces another element in a compound.

Double Replacement reaction

A reaction where the ions of two compounds exchange places in an aqueous solution.

Chemical equilibrium

A state in which the forward and reverse reactions occur at the same rate.

Le Chatelier's Principle

Principle stating that if a system at equilibrium is subjected to a change, the system adjusts to counteract that change.

Energy change in a system

Evidence of a chemical reaction indicating either heat release or absorption, or release of light.

Gas release

Evidence of a chemical reaction where gas is produced during the process.

Sudden appearance of a solid

Evidence of a chemical reaction indicating precipitation formation.

state of matter

S=Solid

L=Liquid

G=Gas

aq=Aquereous (Dissolved in water.)