- Remind pupils of work about mixtures in unit 7H 'Solutions' and show them examples of mixtures they may have encountered,
eg iron and sulphur, chalk in water, seawater, air, soil, rocks, ink, shaving foam. Elicit what they understand by the term 'mixture',
eg by asking them to draw diagrams to illustrate the particles in elements and compounds and extending this to mixtures, and establish their criteria for deciding whether something is a mixture or not. Introduce the idea that compounds can be represented by a formula whereas mixtures vary in composition,
eg by showing samples of compounds together with molecule models, and contrasting these with samples of mineral water together with labels from bottles showing that the water is a mixture.
- Ask pupils for their ideas of the meaning of 'pure' when applied to a material,
eg What is 'pure' orange juice? What is 'pure' water? Establish what is meant by 'pure' and 'impure' and link back to the illustrations of elements, compounds and mixtures made earlier in the activity. Reinforce using simulation software illustrating elements, compounds and mixtures.
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- name some everyday mixtures,
eg air, seawater, mineral water
- identify that mixtures can vary in composition
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