Chemical Reactions

Classify chemical reactions. Identify the characteristics of different classes of chemical reactions.

A synthesis reaction is a reaction in which two or more substances react to produce a single product. When two elements react, the reaction is always a synthesis reaction.

Two compounds can also react to create one compound in a synthesis reaction.

In a combustion reaction, oxygen combines with a substance and releases energy in the form of heat and light.

Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.

Not all combustion reactions are synthesis reactions!

A decomposition reaction is one in which a single compound breaks down into two or more elements or new compounds. AB A + B

Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.

A reaction in which the atoms of one element replace the atoms of another element in a compound is called a single replacement reaction.

A + BX AX + B

Metal replaces hydrogen or another metal.

A metal will not always replace a metal in a compound dissolved in water because of differing reactivities. An activity series can be used to predict if reactions will occur.

Halogens frequently replace other halogens in replacement reactions. Halogens also have different reactivities and do not always replace each other.

Double replacement reactions occur when ions exchange between two compounds. AX + BY AY + BX

The solid product produced during a chemical reaction in a solution is called a precipitate. All double replacement reactions produce either water, a precipitate, or a gas.