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Hydrocarbons Compounds containing hydrogen and carbon only

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Presentation on theme: "Hydrocarbons Compounds containing hydrogen and carbon only"— Presentation transcript:

1 Hydrocarbons Compounds containing hydrogen and carbon only
We get them from crude oil They are made up of molecules A molecule is made up of 2 or more atoms joined by covalent bonds. Hydrogen is in group 1 and has 1 outer electron Hydrogen can form one bond Carbon is in group 4 and has 4 outer electrons Carbon can form 4 bonds

2 ALKANES H C Methane CH4 Structural Formula Molecular Formula Name C C
A family of hydrocarbons H C Methane CH4 Structural Formula Molecular Formula Name C C H C2H6 Ethane

3 ALKANES C C H C Propane C3H8 H C C C4H10 Butane

4 ALKANES Pentane C5H12 H C C C

5 Hexane – How many hydrogens?
C6 H H C H

6 Each carbon in the chain has a hydrogen above and below so multiply 6 by two = 12
There is also a hydrogen at each end. Add 2. Total number of hydrogens = (2x6) + 2 = =14 C H

7 Give the complete formula for each of these hydrocarbons
Give the complete formula for each of these hydrocarbons. You are given the number of carbons. C8 C10 C15 C31 C100 Cn H18 (2 x 8) + 2 = =18 H22 (2 x 10) + 2 = = 22 H32 (2 x 15) + 2 = = 32 H64 (2 x 31) + 2 = = 64 H202 (2 x 100) + 2 = = 202 H2n + 2 (2 x n) + 2

8 Hydrogen and carbon only
Hydrocarbons Hydrogen and carbon only Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10 Pentane C5H12 Hexane C6H14 Heptane C7H16 Octane C8H18 Nonane C9H20 Decane C10H22 My Elephant Prefers Buns Pity He Has Only Nice Doughnuts Alkanes General formula CnH2n+2

9 H CH3CH3 C C H CH3CH2CH3 C C C Shortened structural formula

10 Isomers H C C H C C C Both butane Both C4H10 Same molecular formula
Different structural formula

11 In your jotter: Draw the 3 isomers of pentane At least 3 isomers of hexane

12 CYCLOALKANES Cycloalkanes are ring compounds The first cycloalkane is: H C C C Cyclopropane C3H6

13 The second cycloalkane is:
Cyclobutane C4H8

14 The third cycloalkane is:
Cyclopentane C5H10

15 The fourth cycloalkane is:
Cyclohexane C6H12

16 General formula CnH Cycloalkane Molecular Formula
Cyclopropane C3H6 2 x 3 = 6 Cyclobutane C4H8 2 x 4 = 8 Cyclopentane C5H x 5 = 10 Cyclohexane C6H x 6 = 12 Cycloheptane C7H x 7 = 14 Cyclooctane C8H x 8 = 16 General formula CnH 2n

17 ALKENES C C H Ethene C2H4 Double bond
Alkenes are hydrocarbons which have a double bond Double bond C C H Ethene C2H4

18 H C C C Propene C3H6 H C C C Butene C4H8

19 General formula CnH Alkene Molecular Formula Ethene C2H4 2 x 2 = 4
Propene C3H6 2 x 3 = 6 Butene C4H8 2 x 4 = 8 Pentene C5H10 2 x 5 = 10 Hexene C6H12 2 x 6 = 12 General formula CnH 2n

20 Write the molecular formula of:
a) the alkane with 6 carbons b) the alkane with 24 hydrogens c) the cycloalkane with 20 carbons d) the alkene with 100 hydrogens Draw the structural formula of: a) the alkene with 5 carbons b) the cycloalkane with 7 carbons Give the general formula of a) the alkanes b) the alkenes c) the cycloalkanes Copy and complete: a) Isomers have the same ____ formula but different ___ formula Draw 2 isomers of heptane and 2 isomers of butene and 2 isomers of cyclopropane What is meant by a hydrocarbon? What is meant by a molecule? What is produced when a hydrocarbon burns? Which would have higher boiling point propane or pentane? Which would be more flammable octene or butene? Which would be more viscous cyclopropane or cyclooctane?

21 E A H H C C C C Single bond Double bond Hydrocarbons Alkanes Alkenes
Ethane Ethene

22 The Bromine Water Test Place a small amount of each hydrocarbon in a test tube. To each add a little bromine water. Bromine water is a brownish colour and when dilute is yellowish. Set out your results by drawing up a table as shown below Hydrocarbon Formula Result of test Hexane C6H14 Hexene C6H12 Heptane C7H16 Octane C8H18 Cyclohexane C6H12

23 Br Br Br2 Test for ALKENES C C H H C C H H H ETHENE Bromine water

24 1 Write out full structural formulae to show the reaction between:
Propene and bromine water Butene and bromine water Complete the following equations by putting in the missing compounds (first one is done for you). C5H10 (pentene) + Br2  C5H10 Br2 C6H12 (hexene) + Br2  C6H12 Br2 _____ (_______) + Br2  C8H16 Br2 C4H8 (butene) + Cl2  _________ C5H10 (pentene) + ____  C5H12

25 ALKANE C C H ethane Single bonds only Saturated

26 ALKENE C C H ethene Unsaturated Has a C=C double bond.


28 Heat Hydrocarbon oil (C12H26) Cracking Aluminium oxide catalyst Product gas water Do not remove heat before taking the tube out of the water! The gas produced decolourised bromine water – it contained an alkene. The large liquid molecules have been broken (cracked) into smaller gas molecules. Thermal cracking produces more useful small molecules from less useful large molecules.

29 1 C12H26  C10H22 + ______ ( ) 2 C18H38  C12H26 + ______ ( ) 3 C20H42  C10H20 + ______ ( ) 4 C30H62  C10H22 + C11H22 + ______ ( ) 5 C19H40  C12H24 + C6H12 + ______ ( ) 6 ______ ( )  C4H8 + C4H10

30 H H C H C H C

31 H C H C C H H

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