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Learn About the Conservation of Mass in Chemical Reactions

In this worksheet, students will learn about the conservation of mass in simple reactions.

'Learn About the Conservation of Mass in Chemical Reactions' worksheet

Key stage:  KS 3

Year:  Year 8 Science worksheets

Curriculum topic:   Chemistry: Atoms, Elements and Compounds

Curriculum subtopic:   Conservation of Mass

Difficulty level:  

Worksheet Overview

Have you ever seen magnesium being heated?


burning magnesium


When magnesium is heated in a flame, it mixes with oxygen in the air, turning it into magnesium oxide. You get a spectacular bright light as a result!


If we measured the mass of the magnesium before the experiment and the magnesium oxide produced, we could work out how much oxygen has reacted with the magnesium.


Magnesium + Oxygen → Magnesium oxide

        20 g      +      15 g      →         35 g


As you can see, the total mass of the two substances before is the same as the substance produced! This is called the Law of Conservation of Mass.




So how is this possible? It's all to do with atoms. When a chemical reaction takes place, atoms in a starting substance rearrange themselves and join back together to form a new substance. But, the number of atoms will still be the same before and after the reaction. 


Let's try some questions about conservation of mass together.


woman thinking

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