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Chemical Reactions Terms


A substance dissolved in water.

Balanced Equations

A description of a chemical reaction that gives the chemical formulas of the reactants and the products of the reaction. Coefficients indicate the number of each molecule present in the reaction. These coefficients can be changed so as not to violate the Law of Conservation of Mass.


Numbers inserted before chemical formulas in an equation to ensure that an equation is balanced.

Combustion Reaction

A chemical reaction between a fuel and oxygen that produces heat and light as well as carbon dioxide and water.


A reaction in which a compound is broken down into simpler compounds or elements.

Double Replacement

Also known as a metathesis reaction. A reaction in which two reactants trade partners. Here's an example: AB + CD → AC + BD.


The process of driving an electrical current through a reaction mixture.


A process that absorbs heat.


A process that releases heat.

Law Of Conservation Of Mass

The law that states there is no change in total mass during a chemical change.

Physical Change (or Physical Reaction)

A change that does not transform one substance into another substance, such as freezing or melting. That is to say, no new types of molecules are formed during a physical change.


An insoluble substance that has been formed after the conclusion of a reaction.


The compounds that exist after the conclusion of a reaction. It's also the new molecules that are formed as a result of a chemical reaction.


The components that exists before a reaction takes place. It's also the molecules present at the start of a reaction that will combine to form the products.

Single Replacement

A reaction in which one component of a compound is replaced by a new component. Here's an example: AB + C → A + BC.

Skeleton Equation

An equation that identifies the reactants and products but the equation is not necessarily balanced.


The relationship between the relative quantities of atoms or molecules taking part in a reaction or forming a compound.

Synthesis Reaction

The formation of a complex product from simpler reactants. Here's an example: A + B → AB.

Thermal Decomposition Reaction

A decomposition reaction initiated by heat.

Word Equation

An equation in pure word form with no elemental symbols or numbers.

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