| Method |
Precise Learning Objective |
Linked |
Question / Activity
(Designed for maximum working out) |
Stepping Stones |
Pitstop Check
(Thinking Map) |
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Hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules. |
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What is cracking? Ask students to recall or work out what the term thermal decomposition means |
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Cracking can be done by various methods including catalytic cracking and steam cracking. |
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Describe the conditions required for catalytic cracking? Model the idea of cracking using diagrams and pupil demos |
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Students should be able to describe in general terms the conditions used for catalytic cracking and steam cracking. |
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How is cracking done using steam? Students construct word or symbol equations to show the process of cracking with steam |
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The products of cracking include alkanes and another type of hydrocarbon called alkenes. |
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What are the products of cracking? demo cracking to show the products formed |
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Students should be able to balance chemical equations as examples of cracking given the formulae of the reactants and products. |
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What is the balanced equation for the cracking of this alkane?
C15H32 --> 2C2H4 C3H6 _______ demo and example of how to complete cracking equations and then give a range for students to complete |
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Alkenes are more reactive than alkanes and react with bromine water, which is used as a test for alkenes. |
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Why do do alkenes react with bromine water, but alkanes don't? Teach students that C=C bond in alkenes and that is what makes them different to alkanes |
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Students should be able to recall the colour change when bromine water reacts with an alkene. |
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What is the chemical test and positive result for identifying alkenes? Class practical - identifying unknown hydrocarbons using bromine water |
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There is a high demand for fuels with small molecules and so some of the products of cracking are useful as fuels. |
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Why is cracking of hydrocarbons so important? Tidying away task: "Why is cracking so important?"
Use images to prompt students if necessary |
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Alkenes are used to produce polymers and as starting materials for the production of many other chemicals. |
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How are alkenes used in chemical industry? |
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Students should be able to give examples to illustrate the usefulness of cracking. They should also be able to explain how modern life depends on the uses of hydrocarbons. (For Combined Science: Trilogy and Synergy students do not need to know the formulae or names of individual alkenes.) |
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How does modern life depend on the uses of hydrocarbons? |
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