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Crude oil is a mixture of hydrocarbons
  • Crude oil is an extremely valuable and increasingly scarce fossil fuel.
  • It is a complex mixture of hydrocarbons.
  • The composition of crude oil varies depending upon where in the world it comes from.
  • Crude oil is the principal raw material for the huge petrochemical industry which produces fuels, polymers, pharmaceuticals and many other products.

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5 b) Crude oil

Students will be assessed on their ability to:


5.6 understand that crude oil is a mixture of hydrocarbons
5.7 describe and explain how the industrial process of fractional distillation separates crude oil into fractions
5.8 recall the names and uses of the main fractions obtained from crude oil: refinery gases, gasoline, kerosene, diesel, fuel oil and bitumen
5.9 describe the trend in boiling point and viscosity of the main fractions
5.10 understand that incomplete combustion of fuels may produce carbon monoxide and explain that carbon monoxide is poisonous because it reduces the capacity of the blood to carry oxygen
5.11 understand that, in car engines, the temperature reached is high enough to allow nitrogen and oxygen from air to react, forming nitrogen oxides
5.12 understand that nitrogen oxides and sulfur dioxide are pollutant gases which contribute to acid rain, and describe the problems caused by acid rain
5.13 understand that fractional distillation of crude oil produces more long-chain hydrocarbons than can be used directly and fewer short-chain hydrocarbons than required and explain why this makes cracking necessary
5.14 describe how long-chain alkanes are converted to alkenes and shorter-chain alkanes by catalytic cracking, using silica or alumina as the catalyst and a temperature in the range of 600–700o
C. 

A question of balance

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 Many chemical reactions can be reversed.  

When this happens we can describe a forward reaction and a back reaction.

Sometimes the forward and back reaction take place at equal rates. When this happens an Equilibrium is established

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Rocket fuel needs to react quickly in order to achieve lift off.


How fast a chemical reaction happens is a very important consideration.

If paint dries too quickly it will become impossible to apply.  

If the fuel in a rocket burns too slowly - the rocket will not get off the ground.

Rates of reaction always involves the measuring of the  time taken for a reaction to happen.

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An Exothermic reaction. Acetylene (Ethyne) releases a lot of energy when it burns.

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​Every chemical reaction has an accompanying change in energy.

Some reactions release energy to the surroundings and are known as Exothermic.

Reactions which take in energy from their surroundings are known as Endothermic

When a chemical reaction releases energy  in a useful form substance involved can be used as a fuel

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  • ​This shows a range of chemical changes - all of which release energy .
  • In some cases the energy release is rather sudden.
  • Listen carefully and try to note down the names of the chemicals involved.
  • For each reaction try to write a word equation.
  • Write a symbol equation for each reaction.
  • What is unusual about the last reaction ?

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In this video you can see how a chemical reaction can be used to power a solid fuel rocket.

In this reaction, the chemical reaction releases energy. This is an example of a very exothermic  reaction. 

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Ethanol is the "alcohol" in alcoholic drinks

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 Ethanol is an organic molecule which has a variety of uses. 

It is a good solvent and it burns cleanly so can be used as a fuel.

Here we will consider two of the methods by which ethanol can be made and examine the advantages and disadvantages of each

metal 

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Ethene is the simplest of the Alkene molecules

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​The Alkenes are another Homologous series of Hydrocarbons. They differ from the Alkanes because they contain in their molecules at least one double bond between two of the carbon atoms.

Because of their double bonds, the alkenes are more reactive than the alkanes and thus they are useful for making new compounds.

Alkenes can be made into polymers - such as polyethene and polystyrene - synthetic materials which have a wide variety of uses

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With just one carbon atom in the molecule, methane is simplest Alkane.

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The Alkane series is a family of hydrocarbons

The technical name for family is a homologous series

The alkane molecules contain atoms of hydrogen and carbon only

The general formula for the alkanes is CnH2n+2


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Organic chemistry is concerned with the compounds of the element carbon. Carbon atoms can form four covalent bonds with a range of other elements

Carbon chains form longer molecules and branches create a greater complexity. 

Atoms of hydrogen, nitrogen and oxygen will bond readily with carbon atoms and can ultimately form the molecules of life including amino acids and proteins.

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Analytical chemistry involves the identification of chemical substances using a variety of methods.

Although modern technology has enabled chemists to analyse and identify a huge range of substances very quickly and accurately some simple test tube reactions can still be quicker and cheaper to perform.


2.44 describe tests for these gases:
hydrogen, oxygen, carbon dioxide, ammonia, chlorine.
2.45 describe how to carry out a flame test
2.46 know the colours formed in flame tests for these cations:
Li+is red,Na+is yellow, K+ is lilac, Ca2+is orange-red, Cu2+is blue-green.
2.47 describe tests for these cations:
 NH4+ using sodium hydroxide solution and identifying the gas evolved, Cu2+, Fe2+and Fe3+using sodium hydroxide solution.
2.48 describe tests for these anions:
Cl, Brand Iusing acidified silver nitrate solution SO42– using acidified barium chloride solutionCO32–using hydrochloric acid and identifying the gas evolved.
2.49 describe a test for the presence of water using anhydrous copper(II) sulfate
2.50 describe a physical test to show whether a sample of water is pure

This video gives a good overview of the main trends in solubility of  the compounds which you will meet at GCSE. 

If you have not already done so you should learn the names and fomulae of the ions shown above and below: 

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The solubility table - you need to learn this.

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This table is important to learn  - so that you can use it to predict what will happen when two solutions are mixed. Some examples are 

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