Definition

A chemical reaction is a process in which one or more substances change into new substances with different properties. Chemical reactions are classified into different types according to how reactants change into products.

1. Combination Reaction

A combination reaction occurs when two or more substances combine to form a single product.

Example:

Magnesium reacts with oxygen to form magnesium oxide.

2. Decomposition Reaction

A decomposition reaction occurs when one compound breaks down into two or more simpler substances.

Example:

Calcium carbonate decomposes into calcium oxide and carbon dioxide when heated.

3. Displacement Reaction

A displacement reaction occurs when a more reactive element replaces a less reactive element in a compound.

Example:

Zinc displaces copper from copper sulphate because zinc is more reactive than copper.

4. Double Displacement Reaction

A double displacement reaction occurs when two compounds exchange their ions to form two new compounds.

Example:

Silver nitrate reacts with sodium chloride to form silver chloride and sodium nitrate.

5. Combustion Reaction

A combustion reaction occurs when a substance reacts with oxygen and releases energy, usually in the form of heat and light.

Example:

Methane burns in oxygen to produce carbon dioxide and water.

Summary of Chemical Reactions