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Identify Chemical Reactions or Physical Changes

In this worksheet, students will identify whether a change is physical or chemical.

'Identify Chemical Reactions or Physical Changes' 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

When a chemical reaction takes place, there are several changes that may occur. These visible changes are called the indicators of a chemical reaction. There are several indicators of reaction:


Colour Change

colour change when chemical is added to a flask of solution


A change in colour is a sign of a chemical reaction. For example, frying an egg is a chemical reaction with a colour change - colourless to white.


Gas Given Off  

TReaction giving off gas


During a chemical reaction, a gas can be produced. This can be seen by bubbles forming in the reaction or by a coloured gas being produced (such as smoke).


Solid Formed  

Precipitate forming


If two solutions are mixed and a solid is formed, this is called a precipitate. A precipitate is an insoluble solid formed by reacting two liquids. For example, when milk goes very sour, a solid is formed.


Temperature Change 

Match burning


An energy change involves a change in temperature (either up or down). For example, the burning of a match involves a release of both heat and light.


In a chemical reaction, one or more new substances are always produced. So it is difficult to reverse a chemical reaction, as atoms have been rearranged. 


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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