- Show pupils a wax candle burning and pose a question,
eg If materials combine with oxygen when burning, why does a candle get smaller and smaller? Provide pupils with additional information,
eg wax is a compound of carbon and hydrogen, and ask the pupils to suggest what is formed when it burns. Establish with pupils what is likely to be formed when hydrocarbons are burned and ask them to suggest what happens to the products.
- Represent the formation of carbon dioxide and water by word equations and/or diagrams. Extend to a range of compounds containing hydrogen and carbon,
eg natural gas, sugar.
- Provide pupils with information about Priestley, Lavoisier and the phlogiston theory of burning, together with a series of questions of various difficulty,
eg
- What did Priestley find out about oxygen?
- What was the phlogiston theory?
- What did Lavoisier contribute to the development of ideas about burning?
Ask pupils to describe what they found out and discuss with them eighteenth-century ideas about burning and how these differ from those we hold today. Ask them how our ideas about particle theory help to explain our views.
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- state that carbon dioxide and water are formed when,
eg wax, natural gas, is burned
- explain that the water and carbon dioxide formed escape into the air
- explain that if the carbon dioxide and water could be collected, there would be no loss of mass
- represent the reactions by word or symbol equations or diagrammatically
- identify from texts answers to questions posed
- summarise evidence about burning
- describe how eighteenth-century ideas about burning differ from those we hold today and summarise the evidence for present-day ideas
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