- Show pupils a range of metal objects or pictures of objects,
eg copper and nickel coins, gold rings, an old gold necklace, a relatively new rusty hinge, a tarnished silver cup, a photograph of a bronze/copper roof, and ask them to describe what has happened to each and what has caused this. Elicit ideas about the effect of air/water and the different effects on different metals.
- Extend to show pieces of potassium, sodium and lithium, which are shiny when freshly cut but which immediately tarnish on exposure to air. Ask pupils to explain why the surfaces become dull. Challenge pupils to say whether these are metals or not, asking them to produce reasons for and against. Refer back to work on the periodic table.
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- describe how metals change due to exposure to the air,
eg iron rusts, silver becomes dull, copper darkens
- identify some metals that corrode readily and some that do not
- give a reason why sodium, potassium and lithium seem to be metals,
eg they are shiny, and a reason why they seem not to be,
eg they are not hard, they can't be left in the air without tarnishing
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