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Identify Chemical Reactions

In this worksheet, students will identify whether a change is physical or chemical, and describe what happens to the atoms involved in a chemical reaction.

'Identify Chemical Reactions ' worksheet

Key stage:  KS 3

Year:  Year 8 Science worksheets

Curriculum topic:   Chemistry: Chemical Reactions

Curriculum subtopic:   Rearrangement of Atoms in Reactions

Difficulty level:  

Worksheet Overview

In a chemical reaction, one or more new substances are produced. Atoms are rearranged during a chemical reaction, but the number of atoms does not change.


chemical reaction


It is therefore difficult to reverse a chemical reaction because the atoms have been rearranged. 


When a chemical reaction takes place, there can be several changes that occur. The following visible changes can be used as evidence that a chemical reaction has taken place


Colour Change

colour change when chemical is added to a flask of solution


Gas Given Off  

TReaction giving off gas


Solid Formed  

Precipitate forming


Temperature Change 

Match burning


However, just because we may see these, it doesn't necessarily mean that a chemical reaction has occurred.

A kettle produces bubbles as its water is boiling, but there's not a chemical reaction going on inside the kettle.

Similarly, when you make a cup of tea, there is a colour change in the water from colourless to brown, but there has not been a chemical reaction. 


cup of tea


The observations described in the two examples above are caused by a physical change, rather than a chemical change. 


So what is a physical change?


A physical change is where a substance just changes state. Physical changes are reversible - we always end up with the same substance we started with but sometimes in a different state. 


diagram to show changes of state


Let's have a go at some questions now.

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