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KS4 Chemistry. Useful Oil. Contents. Useful Oil. Crude oil. Fractional distillation. Physical properties of fractions. Uses of fractions. Summary activities. Crude oil is a mixture . It contains hundreds of different compounds. Some are small but most are large.
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KS4 Chemistry Useful Oil
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities
Crude oil is a mixture. It contains hundreds of different compounds. Some are small but most are large. Nearly all of these compounds contain carbon and hydrogen only. They are called hydrocarbons. Crude oil Hydrocarbons are molecules that contain carbon and hydrogen only.
An oil rig Crude oil is often located underneath the sea bed. Oil rigs or drilling platforms are used to drill through the sea bed to obtain the oil.
Crude oil is a mixture of different sized hydrocarbons. The exact composition depends upon where the oil comes from but typically it contains a lot of big molecules. Hydrocarbons Small molecules Big molecules Medium molecules
These hydrocarbons are vital to our way of life. We use them as highly portable fuels for many forms of transport. We also use them as raw materials from which a huge range of useful everyday substances are made. The importance of oil
Although we can get useful substances from oil, crude oil itself has no uses. In order to make crude oil into useful substances we first have to separate the mixture into molecules of similar size. This is done in an oil refinery. Making oil useful
An oil refinery Crude oil is separated into useful fractions in an oil refinery
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities
Crude oil is split into fractions containing similar sized molecules using fractional distillation. The oil is heated until it vaporises. It then passes up a tall tower that is hot at the bottom but cool at the top. As the vapour passes up this tower the molecules cool and condense back to liquid. cool hot Fractional distillation
Copy the column and arrange the fractions in the right order next to the arrows. cool hot Fractions and boiling points Fuel gas Petroleum Kerosine Diesel Lub. Oil Bitumen
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities
We have already said that, in general, the bigger the molecule the higher the boiling point. B.Pt (oC) No. Carbon atoms The boiling point of hydrocarbons
Here are the boiling ranges of some fractions obtained from distillation of petroleum. Using the previous graph, estimate the size range of the molecules present in each fraction. Boiling point and fraction size 1-5 5-10 9-14 13-17
When hydrocarbons burn they are reacting with oxygen in the air. In general, the smaller the molecule the better it will mix and then react with the air. Flammability of hydrocarbons
Flash points are (roughly) the temperature below which you cannot ignite the substance. Here is some flash points data for oil fractions. Link the molecule to the flash point. Flash points
When we pour a liquid the molecules have to pass each other. The easier they do this, the runnier the liquid is. The molecules in fuel oil and bitumen may contain up to 400 carbon atoms in long chain structures. These chains easily become entangled reducing the runniness of the liquid and so those made up of big molecules tend to be viscous (treacly) not runny. Viscosity of hydrocarbons
In contrast, small molecules are more spherical and tend not to get tangled. They are therefore likely to have a low viscosity (be runny). Smaller molecules Lower viscosity “Runny” Bigger molecules Higher viscosity “Treacly” Viscosity of hydrocarbons
Here are the viscosities of 5 hydrocarbons. The higher the value the less runny the hydrocarbon is. Draw arrows joining the hydrocarbon with the appropriate value. Matching hydrocarbons to their viscosity
Small hydrocarbon molecules are gases or transparent liquids. As the molecules get larger the colour becomes increasingly yellow through to the brown/black colour of bitumen used on roads and roof repairs. Increasing size of molecules Colour of hydrocarbons
We already know that each petroleum fraction consist of hydrocarbon molecules falling within a particular size range. The proportions of the different hydrocarbons present in oil can vary greatly across the world. It is therefore not surprising that the exact nature of the fractions collected will vary both in amount and detailed composition. Nonetheless most crude oil will give rise to some quantity of each type of fraction. Composition of fractions
Using viscosity data for crude oil from different areas of the world, arrange the oils putting those with the smallest molecules first. Viscosity of different crude oil 5 2 3 4 1
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities
Uses of different fractions Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gas Fuel gas Petrol / gasoline Fuel for cars and motorcycles, also used to make chemicals. Naphtha Used to make chemicals. Paraffin / kerosine Fuel for greenhouse heaters and jet engines, manufacture of chemicals. Diesel fuel Fuel for lorries, trains. Fuel and lubricating oil Fuel for the heating systems of large buildings, fuel for ships, lubricating oil. Bitumen Roofing, and road surfaces.
The apparatus below is used to test the products of combustion of a hydrocarbon. Burning hydrocarbons Suction pump ice- water Lime water Candle wax is the hydrocarbon here Liquid collected can be tested with anhydrous cobalt chloride paper (bluepink). any hydrocarbon + oxygen water + carbon dioxide
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities
Glossary • combustion – A rapid reaction between a substance and oxygen that produces heat and light energy. • crude oil – A naturally-occurring mixture of hydrocarbons and other substances. • flammable – A substance that easily catches fire and burns rapidly. • fractional distillation – The process used to separate crude oil into different fractions. • hydrocarbon – A molecule containing only hydrogen and carbon. • viscosity – A measure of how easily a liquid flows.
