Understand What Happens in Thermal Decomposition

Thermal decomposition is a type of chemical reaction that takes place at very high temperatures. These high temperatures break down a reactant into two or more products. The substance being heated doesn't react with any other substance - it is purely the heat that causes it to break down into new molecules. Only certain substances will undergo thermal decomposition.

You have probably come across a thermal decomposition reaction at home. When you bake cakes, the baking soda you add to your ingredients thermally decomposes to help your cakes rise because one of the substances that is released is carbon dioxide gas!

There are two rules that you can use to spot a thermal decomposition reaction.......

1. In a thermal decomposition reaction, there is only ever one reactant.

2. In a thermal decomposition reaction, there are always two or more products.

Here is an example of a thermal decomposition reaction, and its word equation:

Calcium carbonate   →   Calcium oxide + carbon dioxide

       Reactant                                Products

You can often easily work out the name of the reactant by knowing the name of the products in a thermal decomposition reaction. In the example above, we can see that calcium oxide was made because the reactant started with the word calcium. If magnesium oxide was one of the products, we could probably guess that the reactant started with the word magnesium, and if copper oxide was one of the products, then probably the reactant would have started with the word copper. Get it?

Are you ready to have a go at some questions on this tricky topic now?