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L07. Alkanes & Alkenes

Connector: (Grade D) Describe the number of bonds carbon and hydrogen forms. L07. Alkanes & Alkenes. BIG picture. What skills will you be developing this lesson? ICT Numeracy Literacy Team work Self management Creative thinking Independent enquiry Participation Reflection

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L07. Alkanes & Alkenes

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  1. Connector: (Grade D) Describe the number of bonds carbon and hydrogen forms. L07. Alkanes & Alkenes

  2. BIG picture • What skills will you be developing this lesson? • ICT • Numeracy • Literacy • Team work • Self management • Creative thinking • Independent enquiry • Participation • Reflection • How is this lesson relevant to every day life? (WRL/CIT)

  3. Task 1 (Grade C) • Keywords for Task 1: • Task 1: Describe the differences between alkanes and alkenes and explain why they are called hydrocarbons. • Task 1: Extension

  4. New Information for Task 1 • Watch the 3-D models of the alkanes and alkenes on the next slide. • Now write down how many bonds carbon forms with hydrogen. • What is the difference between alkanes and alkenes? Why are they called hydrocarbons? • Share your answer with a partner. • Pairs feed back one of their answers to the rest of the class, ‘passing’ if their answer has already been given. • Share your answer with a partner. • Pairs feed back one of their answers to the rest of the class, ‘passing’ if their answer has already been given.

  5. Alkanes H H C methane, CH4 H H H H ethane, C2H6 C C H H H H H H H propane, C3H8 C C H C H H H H

  6. H H C C H H or Ethene - formula

  7. Task 1: Answers Carbon forms 4 bonds with hydrogen. Alkanes consist of atoms held together by single bonds (C-C), alkenes contain carbon atoms joined by double covalent bonds (C=C). Hydrocarbons are compounds that consist of hydrogen and carbon atoms only.

  8. Task 1: Review Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

  9. Alkanes all have very similar structures. They have a CH3 at each end of the molecule. What differs is the number of CH2 groups between the two ends. These all consist of carbon and hydrogen only and every carbon has four single covalent bonds. It is possible to build up a series by simply adding an extra CH2 group This leads to a general formula of CnH2n+2 hydrogen carbon n= 1 n=2 n=3 n=4 Homologous Series

  10. Although normal chemical formula - like C5H12 - are used to describe alkanes they do not convey which atom is joined to which other atom. To get around this we often used displayed formula to describe organic molecules. Displayed formula show which 4 atoms each carbon is bonded to but even these do not show the actual 3D shapes. For that we use models. H H C H H Formulae and Models of Alkanes methane, CH4

  11. New Information for Task 2 • Watch presentation 001: • Name the alkanes and alkenes on the next slide • Watch video 001 and demonstration on test for unsaturation: • In your groups, carry out activity 1.7 – making models of alkanes and alkenes

  12. Copy the Table and complete the empty boxes. Activity alkene C5H10 alkane C8H18 alkene C4H8 alkane C10H22

  13. What are alkenes? No. ofcarbon atoms Molecularformula Name 2 3 4 5 6 The alkenes are a homologous series of hydrocarbons with the general formula CnH2n and names ending –ene. Alkenes contain a carbon – carbon double bond and so are unsaturated. C2H4 ethene C3H6 propene C4H8 butene C5H10 pentene C6H12 hexene

  14. What will be the formula for alkanes containing the following numbers of carbons? Activity C12H26 C16H34 C31H64 C19H40

  15. Task 2 (Grade B) • Keywords for Task 2: • Task 2: Describe the use of molecular formulae and displayed formulae.

  16. Task 2: Answers

  17. Task 2: Review Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

  18. New Information for Task 3 • Describe the test for alkenes. • Task 2: Extension: Explain why the bromine water become colourless and how it works.

  19. Task 3: (Grade A/A*) • Task 3: • Task 3: Extension • Keywords for Task 3:

  20. Task 3: Answers

  21. Task 3: Review Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

  22. Review Watch interactive 001 Match the formulae and names of the structural formulae of the alkanes and alkenes. Identify the hydrocarbons from the list below and give your reasons: ( CH4, C2H6, C2H4, C2H5OH, C2H4Br2)

  23. 1 2 3 4 5 6 7 8 9

  24. Answers

  25. Review of lesson

  26. Homework • Homework task: • Due date: • Criteria for Grade C: • Criteria for Grade B: • Criteria for Grade A/A*:

  27. Keywords: • Alkanes • Alkenes • Covalent bond • Displayed formula • Hydrocarbon • Saturated • Unsaturated. Put your hand up if there is any key word that you don’t know the meaning of.

  28. Technicians’ List

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