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Describe What Happens in Thermal Decomposition

In this worksheet, students will describe thermal decomposition reactions.

'Describe What Happens in Thermal Decomposition' worksheet

Key stage:  KS 3

Year:  Year 7 Science worksheets

Curriculum topic:   Chemistry: Chemical Reactions

Curriculum subtopic:   Types of Chemical Reactions

Difficulty level:  

Worksheet Overview

Thermal decomposition is a type of chemical reaction that takes place at very high temperatures. These high temperatures break down a substance 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.


experiment with Bunsen burner


it is quite common for thermal decomposition reactions to take place. 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!


chocolate cake


When calcium carbonate, a green powder, is heated it thermally decomposes into copper oxide (a black powder) and carbon dioxide gas:


Calcium carbonate   →   Calcium oxide + carbon dioxide


       Reactant                                Products


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

Reactants are the chemicals that are put into a chemical reaction, they are found on the left of a word equation.


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

Products are the chemicals that are made as a result of the chemical reaction. They are found on the right of a word equation, after the arrow.


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


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