Science at key stage 3 (Year 8)
Unit 8E: Atoms and elements
Section 7: b. How can we represent the changes when new materials are made?
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Objectives |
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- to predict what might be formed from a chemical reaction between elements
- to heat metals in air safely
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Activities |
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Outcomes |
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Children: |
- Invite pupils to investigate one or more simple reactions first hand,
eg what happens when magnesium ribbon is heated strongly in air. Encourage pupils to predict what the product might be on the basis of their prior work. Suggest that they identify and evaluate the product by comparing its appearance and behaviour with that of a known sample of magnesium oxide. Similar experiments could be carried out with zinc and copper to form their oxides.
- Ask pupils to represent the reactions as in the previous activity and to predict what might be formed in other reactions.
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- predict the product of some simple reactions,
eg zinc oxide from zinc and oxygen, iron sulphide from iron and sulphur
- interpret the names and/or formulae of binary compounds in terms of the elements of which they are composed
- make a sample of an oxide safely
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Points to note |
- Teachers may need to explain that it is not true that all chemical reactions involve elements as reactants and compounds as products. Pupils will consider reactions between compounds in later units.
- Pupils will need time to practise using the chemical names of compounds,
eg making the change from oxygen to oxide.
- It is helpful for pupils to become familiar with formulae for common compounds and to relate these to models showing the numbers of atoms. Teachers will be able to judge how far to take explanations of differences in formulae with different pupils.
- Extension: list, for some pupils the formulae of the products of the reactions seen and introduce the idea of 'combining power', using a simple model,eg card cut-outs of elements; ball-and-spoke models. Ask pupils to use the models to predict the formulae of other metallic oxides, chlorides and sulphides. It is helpful to be explicit that the models are not representations of real atoms.
Safety
- when magnesium is heated, eye protection should be used and the burning metal should not be looked at directly
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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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