Chemical reactions: decomposition
Lesson details
Learning outcome
I can describe what happens during decomposition reactions, and write chemical equations to show these.
Key learning points
- Decomposition reactions involve a single compound breaking down into two or more products.
- Decomposition reactions usually require heat, light, or electricity, to occur.
- When metal carbonates decompose upon heating, they typically form metal oxides and carbon dioxide gas.
Keywords
Decompose - When a substance decomposes it undergoes a decomposition reaction.
Decomposition - A type of reaction in which a reactant compound breaks down into two or more products.
Common misconception
Pupils often struggle to understand that not all reactions consist of two substances mixed together to cause a reaction.
Show the symbol equation and how the reactants are rearranged to form the products.
Teacher tip
Pupils can work together to obtain the results, give students a timescale of what constitutes no thermal decomposition, i.e. if there is no change in 3 minutes consider that thermal decomposition has not taken place.
Equipment
Boiling tubes, metal carbonates, clamp and stand, heat resistant mat, bung with delivery tube, spatula, limewater.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What are common signs that a chemical reaction is taking place?
Q2.In a chemical reaction, what happens to the atoms of the reactants?
Q3.What happens to the mass of the products compared to the mass of the reactants in a chemical reaction?
Q4.What type of reaction involves a substance combining with oxygen?
Q5.To test for carbon dioxide, you would bubble the gas through . If carbon dioxide is present, the solution turns milky (cloudy).
Q6.Which of the following chemicals are reactants in this reaction?
zinc + hydrochloric acid → zinc chloride + hydrogen
Assessment exit quiz
6 Questions
Q1.What is a decomposition reaction?
Q2.Decomposition reactions usually require , light, or electricity to occur.
Q3.What gas is commonly produced when metal carbonates decompose?
Q4.Which of the following is a decomposition reaction?
Q5.When metal carbonates decompose upon heating, they typically form metal and carbon dioxide gas.
Q6.Which of the following reactions represents the decomposition of water?
To help you plan your 8 science lesson on: Chemical reactions: decomposition, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 8 science lesson on: Chemical reactions: decomposition, 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.
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