Useful products from crude oil

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C4.11 Hydrocarbons
Hydrocarbons are compounds which contain only the elements carbon and hydrogen.  Crude oil is a mixture of different sized hydrocarbon molecules. These hydrocarbons are basically fuels such as petrol.
Task C4.11 Pick out the hydrocarbons in the following list CH₄, CH₃OH, C₆H₆, C₂H₆, H₂O, C₈H₁₈, C₄H₈, C₂H₃N, C₅H₁₂, C₆H₁₄.

C4.12 Fractional distillation of crude oil
The fractional distillation of crude oil is the process which gives us the different substances (fractions) made from crude oil. The crude oil is pumped in to the fractional column from the bottom. The heat is applied at the bottom of the fractionating column. The different fractions are obtained in different positions in the column.
Top 70^oC, small molecules, light colour, runny, easy to light
               Gases
             Petrol
                Naptha
                Kerosene
             Diesel
             Lubricating oil
                Fuel oil
             Bitumen
Bottom 360^oC, large molecules, dark colour, viscous, hard to light
www.lgfl.net 
http://www.bbc.co.uk/schools/gcsebitesize/chemistry/usefulproductsoil/oil_and_oilproductsrev5.shtml
Task C4.12 Draw diagrams to show the relative sizes of molecules of gas, diesel and bitumen.

C4.13 The size of molecules and boiling point
As the size of a hydrocarbon molecule increases the boiling point increases.  If it has a low boiling point it is very volatile (forms a vapour easily).  If it has a high boiling point it is not volatile.

TaskC4.13 

C4.14 Uses of fractions from crude oil

Butane gas for camping
C4.15 Complete and incomplete combustion
Complete combustion
Happens with plenty of oxygen.  All of the carbon and hydrogen in a hydrocarbon turns to carbon dioxide and water.
Hydrocarbon + oxygen carbon dioxide + water        e.g.
CH₄ + 2O₂ --> CO₂ + 2H₂O

Task C4.15.1 Complete the following equations for complete combustion of hydrocarbons
ethene + oxygen ---> 
C₂H₄ + 3O₂ --->
ethyne + oxygen --->
2C₂H₂ + 5O₂ ---> 
propane +oxygen --->
C₃H₈ +5O₂ --->

Incomplete combustion
Happens if there is not enough oxygen.  The hydrocarbon turns into soot (carbon) and poisonous carbon monoxide as well as carbon dioxide.

Hydrocarbon + oxygen ---> carbon monoxide + water
2CH₄ + 3O₂ ---> 2CO + 4H₂O

Task C4.15.2 Complete the following equations for incomplete combustion of hydrocarbons
ethyne +oxygen --->
Task C4.15.3 Match these combustion products to their formulae: carbon, water, C, sulfur dioxide, CO₂, nitrogen dioxide, NO₂, carbon dioxide, SO₂, carbon monoxide, H₂O, CO.
Story C4.15

C4.16 Chemical tests for carbon dioxide and water
If carbon dioxide is bubbled through limewater it turns milky. We can test for the presence of water using anhydrous copper sulphate which is white. The copper sulphate turns blue when water is added to it.  Cobalt chloride can also be used.  This turns from blue to pink when water is added.
Task C4.16 Show the above information in a suitable table.

C4.17 Cracking
Cracking is the splitting up of long chain hydrocarbons in to smaller chains. Cracking is a form of thermal decomposition. A lot of longer molecules produced from fractional distillation are cracked into smaller ones because there's more demand for products like petrol and Kerosine than for diesel oil. The products include compounds with double bonds such as ethene. For example kerosine could be broken down to octane and ethene.
C-C-C-C-C-C-C-C-C-C-  ----cracking----->    C=C + C=C-C +  
                                                                           C-C=C + C-C
big molecules                                                  small molecule
alkanes                                                            mostly alkenes
single bonds                                                    double bonds
saturated                                                          unsaturated
only good for fuels                                can be made into polymers

C4.18 Industrial conditions for cracking
Industrial conditions for cracking vaporised hydrocarbons are to use a powdered catalyst at about 400ºC to 700ºC. The catalyst could be Aluminium oxide.

C4.19 The products of cracking
Cracking turns big molecules into small molecules which are mostly alkenes.  Some alkanes are also made.

C4.20 Saturated and unsaturated hydrocarbons
Alkanes are saturated hydrocarbons.  They have single C-C bonds only.
Alkenes are unsaturated hydrocarbons.  They have double C=C bonds.
Saturated hydrocarbons are so called because their C atoms have no spare bonds left to join with any more hydrogen atoms. They contain C-C single bonds and each C atom is joined to 4 other atoms. Unsaturated hydrocarbons are so called because they have some spare bonds which could be used to add on some more hydrogen atoms.

C4.21 Natural gas
Natural gas is mostly made up of an alkane called methane CH₄.
News about natural gas

C4.22 The formulae and structures of alkanes

Ethane C₂H₆
    H H
     |   |
H-C-C-H
     |   |
    H H

Propane C₃H₈
    H H H
     |   |   |
H-C-C-C-H
     |   |   |
    H H H

Butane C₄H₁₀
    H H H H
     |   |   |   |
H-C-C-C-C-H
     |   |   |   |
    H H H H

C4.23 Formulae and Structures of alkenes

Ethene C₂H₄
 H  H
  |    |
 C=C
  |    |
 H  H

Propene C₃H₆
    H H  H
     |   |    |
H-C-C=C-H
     |
    H

C4.24 Testing alkanes and alkenes with bromine water

C4.25 Making polymers from small molecules
Polymers like polythene, polypropene and polystyrene are large molecules, which can be formed by combinations of many smaller molecules called monomers.

C4.26 Addition polymers
lots of monomers add together --->  1 addition polymer
Each has C=C bonds                       only single bonds
unsaturated                                       saturated
lots of ethene molecule   --->            1 polyethene molecule
H   H   H  H      H  H                            H  H  H  H  H  H  H  H
 |     |     |     |       |    |                               |    |     |    |    |    |    |    |
C=C + C=C +  C=C + .... --->          -(C- C- C- C-C- C- C- C)-_n
 |    |      |     |       |    |                              |     |    |     |    |    |    |    |
H  H    H   H     H  H                           H  H  H  H  H  H  H  H
Task C4.26 Draw structures and equations as above for the formation of polypropene and polychloroethene.

C4.27 Uses and properties of polymers

Task C4.27