Alkanes and Alkenes Learning Objective – What are the differences between alkanes and alkenes?
Alkanes – a summary • If all the carbon atoms in a hydrocarbon are joined by single bonds. It is saturated. • Saturated hydrocarbons are called alkanes. • All alkanes end with –ane. The front part depends on how many carbons it has. • Alkanes burn well, giving out lots of heat. Many fuels such as petrol, diesel and kerosene contain alkanes. • Apart from burning, alkanes are pretty unreactive.
The Alkanes --A family of Hydrocarbons. The first ten molecules are: Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10 Pentane C5H12 Hexane C6H14 Heptane C7H16 Octane C8H18 Nonane C9H20 Decane C10H22 They have the General Formula CnH2n+2
Methane H C H H H
Ethane C2H6 H H C C H H H H
Propane C3H8 H H H C C C H H H H H
Carbon beginnings. • Meth 1 • Eth 2 • Prop 3 • But 4 • Pent 5 • Hex 6 • Hept 7 • Oct 8 • Non 9 • Dec 10
Alkenes • Alkenes are unsaturated, they have a double bond between two of the carbons. • All alkenes end in the ending – ene. • Alkenes also burn very well, however, they are not normally used as fuels. This is because they are used to make other substances like plastics.
The Alkenes • The Alkenes are a family of Hydrocarbon Molecules which have the General Formula CnH2n The first ten are: Ethene C2H4 Propene C3H6 Butene C4H8Pentene C5H10 Hexene C6H12Heptene C7H14 Octene C8H16Nonene C9H18 Decene C10H20 Undecene C11H22
Ethene C2H4 Ethene is an unsaturatedmolecule H H C C H H ADoubleBond between CarbonAtoms
Propene C3H6 H H Propene is an unsaturatedmolecule H H C C C H H
Answer the following questions in your note books • 1. What does Unsaturated molecule mean? • 2. Why is the ending of a Hydrocarbon Molecule’s name so important? • 3. Draw a Pentane molecule (C5H12) • 4. Draw a Pentene molecule (C5H10) • 5. What does the first part of a Hydrocarbon molecule’s name tell you? • Extra • 6. What do you think a But-2-ene molecule looks like?
Answers • A1. A molecule that contains a double bond is an unsaturated molecule. • A2. It shows which family of hydrocarbons the molecule belongs to. • A5. How many Carbon atoms there are in the molecule • A6. CH3CH=CHCH3