Year 9 · Science
Conservation of mass calculations: Year 9 GCSE bridge
Start here
Focus on conservation of mass in chemical reactions. Open support for “Check Mass Conservation Using Relative Formula Mass”, then explain the idea in your own words.
Understand the key idea
Because atoms are only rearranged, the total mass of reactants equals the total mass of products. This lets you calculate a missing mass: if you know the mass of every substance but one, subtract the known product masses from the total reactant mass. Reactions that appear to gain or lose mass in an open container involve a gas entering or escaping.
Common mix-up
A metal gaining mass when it burns does not break conservation of mass. Oxygen from the air has joined the metal, so the sealed-system total is still unchanged.
Try this first
- Calculate the missing product mass from a reaction table.
- Explain why magnesium gains mass when it burns.
- Decide whether an open or closed system is needed to show conservation.
Ask: Magnesium gets heavier when it burns — how can that not break the rule?
Year 9 learners practise conservation of mass in chemical reactions.
The activities include Check Mass Conservation Using Relative Formula Mass, Apply the Law of Conservation of Mass in Open and Closed Systems, Use Conservation of Mass in Calculations, and related practice. The checked support below includes video, worksheet, teaching. Open a resource in its provider's website and choose the format that best helps the learner explain the idea independently.
Activities covered
Finish one activity, then tap Done to earn one Den Drop ticket. You can earn up to 3 tickets each day.
- Check Mass Conservation Using Relative Formula Mass — support from YouTube — Cognito
- Apply the Law of Conservation of Mass in Open and Closed Systems — support from Oak National Academy
- Use Conservation of Mass in Calculations — support from Oak National Academy
- Calculate Relative Formula Mass — support from YouTube — BBA Science
- Understand the Law of Conservation of Mass — support from Oak National Academy
- Understand the Law of Conservation of Mass in Terms of Atoms — support from Oak National Academy
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Watch it explained
watch a video explanation
GCSE Chemistry: Conservation of Mass
Best for: a clear explanation before you practise
Conservation of mass and balanced symbol equations
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Relative Formula Mass - p80
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Learn it properly
lessons and teaching pages
Understanding chemical reactions: lesson sequence
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questions and activities to try
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Print and finish
worksheets away from the screen
Chemical reactions - KS3 Chemistry
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