Conservation of mass
I can describe what happens to the atoms of reactants as they form products in a chemical reaction.
Conservation of mass
I can describe what happens to the atoms of reactants as they form products in a chemical reaction.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- Atoms are the building blocks that can be combined in different ways to form different substances.
- It is impossible for any atom to be changed into a different type of atom by a chemical reaction.
- All of the atoms in the reactants of a chemical reaction are reorganised to form all of the products of the reaction.
- It is impossible to make a particular product without all the atoms that it needs.
- The law of conservation of mass can be applied to a closed system, or a non-enclosed system that takes in/gives out gas.
Keywords
Conservation of mass - Conservation of mass means that the combined mass of the starting reactants equals the combined mass of the products formed.
Closed system - A closed system is one in which matter cannot enter or leave the observed environment, allowing only energy transfer between the system and its surrounding environment.
Reactant - Reactants are the elements or compounds before a reaction takes place.
Product - Products are the elements or compounds that are formed after a reaction has taken place.
Atom - Atoms are the building blocks of all matter.
Common misconception
Pupils can struggle to link chemical formulae to what is happening on the atomic level and to what they observe during a chemical reaction.
Reinforce via demonstrations, modelling and diagrams via Johnstone's triangle. One simple demo (e.g. magnesium + oxygen) = one model, one diagram and one chemical reaction equation. Use progressively more complicated demos and build up from there.
To help you plan your year 10 chemistry lesson on: Conservation of mass, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 10 chemistry lesson on: Conservation of mass, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 chemistry lessons from the Calculations involving masses unit, dive into the full secondary chemistry curriculum, or learn more about lesson planning.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
Loading...
Starter quiz
6 Questions
carbon dioxide
magnesium oxide
calcium carbonate
sodium chloride
silver bromide
ammonia
gases shown by the state symbol (g).
a gas as it is steam.
2H₂ (g) + O₂(g) → 2H₂O(g)
of oxygen (2) and hydrogen (4) in the reactants and products.
hydrogen + oxygen → water (dihydrogenoxide)
Exit quiz
6 Questions
oxygen
12 g - 10 g = 2 g
open
Some could have escaped into the atmosphere.