Topic 7a: Hydrocarbons and Crude oil

What is crude oil?

• A sticky black substance

• A mixture of hydrocarbons

How was crude oil formed?

• millions of years ago marine organisms died

• Bodies fell to bottom of ocean

• Covered by sediment

• High pressure and millions of years compressed into crude oil

What is crude oil used for?

Is separated using fractional distillation to produce a large number of useful products

eg:

• Many of the fuels on which we depend for our modern lifestyle, such as petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases, are produced from crude oil.

• Many useful materials on which modern life depends are produced by the petrochemical industry, such as solvents, lubricants, polymers, and detergents.

What is a homologous series

Series of compounds with the same general formula, same functional groups and similar chemical properties

Explain how crude oil is separated into useful components

• Crude oil is heated to 360 degrees and enters the fractional distillation column as a gas

• Hot gases rise up the column and gradually cool down

• Each fraction condenses and forms a liquid at its boiling point

• Separating by boiling point

• Larger molecules eg bitumen, condense at the bottom

• Smaller molecules eg L.P.G leave the chamber as a gas at the top

What is a hydrocarbon

Contains hydrogen and carbon only

What does saturated mean

Contain the maximum number of hydrogen’s and only have single covalent bonds between carbons

What are alkanes

The simplest type of hydrocarbons are called alkanes

• They are unreactive → only contain single c-c bonds

• But do combust really well → make excellent fuels

The first four members of the alkanes are:

• methane, ethane, propane, and butane.

Counting carbons

1 - Meth

2 - eth

3 - prop

4 - but

Combustion of hydrocarbons

• An exothermic reaction when hydrocarbons react with oxygen

Complete Combustion:

• Produces carbon dioxide and water vapour

• Increases greenhouse effect

• Increases global warming

Incomplete Combustion:

• Produces carbon (soot) and carbon monoxide

Properties of hydrocarbons

• The shorter the molecules, the more runny the hydrocarbon is - that is, the less viscous it is

• The shorter the molecules, the lower their boiling point is. So, the shorter the molecules, the lower the temperature at which they vaporise or condense

• The shorter the molecules, the more flammable the hydrocarbon is

So hydrocarbons with very long carbon chains are viscous, have very high boiling points and are not very flammable

What is cracking

• In cracking hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules

• There is a high demand for fuels with small molecules, and so some of the products of cracking are useful as fuels.

• The products of cracking include alkanes and another type of hydrocarbon called alkenes

What type of reaction is cracking

Thermal decomposition

What are the different methods cracking can be done by

Catalytic Cracking:

• The long-chain hydrocarbons are heated to vapourise them, then the vapour is passed over a hot, powdered catalyst

Steam Cracking:

• The long-chain hydrocarbons are heated to vapourise them, then the vapour can be mixed with steam and heated to a very high temperature