1. Unit 2
Hydrocarbons

2. What are Hydrocarbons?
A hydrocarbon is a molecule which contains only the elements Carbon and Hydrogen.
Hydrocarbons are obtained from the Fractional Distillation of crude oil.
We use them for fuels in cars (octane) and in cookers (methane).

3. How Do We Group All These Hydrocarbons Together?

4. Hydrocarbons Homologous Series Alkanes Alkenes Cycloalkanes
a group of chemically similar compounds which can be represented by a general formula.
Physical properties change gradually through the series
Alkanes
Alkenes
Cycloalkanes

5. Alkanes Methane Monsters Ethane Eat Propane Pupils Butane But
Pentane Prefer
Hexane Hairy
Heptane Haggis
Octane Or
Nonane Nice
Decane Dinners

6. Alkanes - Methane 3D Full Structural  2D Full Formula Structural
Get them to make a model of methane to show that it doesn’t sit flat on the table but does in fact have a 3D shape. Also C = 4 bonds and H = 1

7. Alkanes Each member can be represented in three different ways:
Methane Propane
Full Structural
Formula
Shortened Structural
Molecular Formula

8. Alkanes
The Alkanes are a family of hydrocarbons and all share the same chemical properties:
Single Carbon to carbon bonds
( - C – C - )
All end in -‘ane’
Saturated hydrocarbons
All share a General Formula

9. Shortened Structural Formula Full Structural Formula
Alkanes
Alkane
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Boiling
Point
Methane
(1)
-164
Ethane
(2)
C2H6
CH3CH3
- 89
Propane
(3)

10. Shortened Structural Formula Full Structural Formula
Alkanes
Alkane
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Boiling
Point
Methane
(1)
CH4
-164
Ethane
(2)
C2H6
CH3CH3
- 89
Propane
(3)
C3H8
CH3CH2CH3
- 42

11. Alkanes Butane (4) Pentane (5) Hexane (6) Alkane (Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Boiling
Point
Butane
(4)
Pentane
(5)
Hexane
(6)

12. Alkanes -1 36 69 Butane (4) C4H10 CH3CH2CH2CH3 Pentane (5) C5H12
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Boiling
Point
Butane
(4)
C4H10
CH3CH2CH2CH3 -1
Pentane
(5)
C5H12
CH3CH2CH2
CH2CH3 36
Hexane
(6)
C6H14
CH2CH2CH3 69

13. Alkanes Heptane (7) Octane (8) Alkane (Carbon Atoms) Molecular Formula
Shortened Structural Formula
Full Structural Formula
Boiling
Point
Heptane
(7)
Octane
(8)

14. Alkanes C7H16 98 C8H18 CH3CH2CH2CH2 CH2CH2CH3 Heptane (7) Octane (8)
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Boiling
Point
Heptane
(7)
C7H16
CH3CH2CH2CH2 CH2CH2CH3 98
Octane
(8)
C8H18
126

15. General Formula for alkanes is CnH2n+2
The number of Hydrogen atoms = 2 times the number of Carbon atoms plus 2
General Formula for alkanes is CnH2n+2

16. Alkanes – Physical Properties
M.p/b.p – gradual increase from methane to octane
Viscosity - increases as you move down the group
Colour – darker in colour as you move down the group

17. Uses of Alkanes Name of Alkane Use Methane
Fuel for cooking and heating
Butane
Used in barbecues and camping stoves
Octane
One of the compounds in petrol