Science at key stage 3 (Year 8)
Unit 8E: Atoms and elements
Section 6: a. How can we represent the changes when new materials are made?
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Objectives |
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- that atoms of elements combine to form molecules of compounds
- that in chemical changes new substances are formed
- to represent and explain chemical reactions by word equations, models or diagrams
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Activities |
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Outcomes |
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Children: |
- Show pupils some reactions between elements,
eg
- hydrogen and oxygen
- sodium and chlorine
- carbon and oxygen
- copper and sulphur
and ask them to record their observations in terms of the appearance of the reactants and the products and to represent the reactions by word equations, simulation software, models or diagrams, making clear that when the compound is formed the atoms join. Help pupils to represent the compounds formed by formulae and models. Ask pupils to explain individual reactions in these terms and to question others about their representations.
- Extend by showing that water can be split into hydrogen and oxygen by electrolysis.
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- describe what happens in some chemical reactions and name the product
- explain compound formation in terms of atoms joining,
eg using equations, diagrams, models
- show understanding of compound formation in asking questions about others' representations of chemical reactions
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Points to note |
- Pupils will have seen the burning of some elements in oxygen in unit 7F 'Simple chemical reactions', where they first encountered word equations.
Safety
- eye protection and safety screens should be used. Ensure pupils are at a safe distance. Sodium is corrosive and highly flammable, chlorine is toxic and irritant. Some of these reactions are violent. With copper and sulphur there is a risk of producing toxic and irritant sulphur dioxide
- hydrogen and oxygen: don't explode more than 300 cm3 hydrogen indoors. Hearing protectors are needed if a large volume is exploded outside
- sodium and chlorine: place dry sand (50p size) on a heatproof mat. Place a piece of cleaned-up sodium on a crucible lid, ignite, quickly invert a gas jar of chlorine over it
- copper and sulphur: use about 3g copper and 1.5g powdered roll sulphur in a borosilicate boiling tube. Insert a plug of mineral wool in the top. Heat until the reaction starts
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This unit is divided into sections. Each section contains a sequence of
activities with related objectives and outcomes. You can view this unit by
moving through the sections or print/download the whole unit.
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