Chemistry - Feuls From Oils

These cards are for AQA GCSE revision and in them have five sub-sub topics which are:

1. Alkanes     2. Separating Creud Oil     3. Burning Feuls     4.Problem Fuels     5. Better Feuls

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Alaknes - Crude Oil, Hydrocarbons and Alkanes

Crude oil is a fossil fuel. They are formed from ancient single celled plantsand animals that live in the sea that were buried in sediments when they died. The remains were compressed and heated with chemical reactions taking place converting into the oil that we use.

Crude oil is a compound made up of mostly hydrocarbons. The hydrogens join with the carbon atoms that are joined together in chains. These are mostly alkanes. 

The alkane names are decided on the amount of carbons. One carbon means that it is called methane, two carbons means that it is ethane and three carbons mean that it is called propane.

The general formula for an alkane is CnH2n+2.

The atoms in a hydrocarbon are covalently bonded and are saturated meaning that they are made up of only single bonds.

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Separating Crude Oil - Separtating Mixtures and Fr

A mixture consists of two or more elements or compounds but not chemically combined, therefore the subsatnces can be separated through physical methods such as filtration and distillation.

Fractional distilation is used mainly to separate a liquid from a liquid. It boils the mixture until the liquid with the lower boiling point evapourates where the vapour will condense leaving the rest of the mixtures.

Fractional distillation can be used to separate hydrocarbons from crude oil however, the boiling pint of the hydrocarbon depends on the size and the size decides many other things.

The bigger the size the less the volatility and flamability and the greater the boiling point and the viscosity.

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Separating Crued Oil - Oil Fractionation and Uses

Oils are separted to their different boiling points in a fractionating column.

Vapours are sent up the column, the lowest part of the column is the hottest and when it is cool enough for the vapour to condense.

The hydrocarbon will then flow out of the column. This is a continuous process.

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Burning Fuels

Coal is made up of mostly carbon. Complete combustion occours when it is burnt with a large supply of air. If there is complete comustion the the product formed is carbon dioxide however if there is incomplete combustion then carbon monoxide or carbon is formed. Carbon monoxide is a toxic gas and causes headaches, sickness, fainting and even death.

Natural gases are mostly methane and some other alkanes. When methane is burned with the presence of oxygen carbon dioxide and water is formed. The incomplete combustion of methane also causes the production of caron monoxide and carbon.

When crude oil is burned it is mainly for petrol. In petrol there is octane and when burned it forms the same products as natural gases. When crued oil is burned particulates form, also known as soot, high levels of particulates in the air can often lead to death, asthma, brnchitis and other respiratory diseases.

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Problem Fuels

Infrared radiation the reaches the Earth's surface from the sun it stopped from escpaing the atmosphere by greenhouse gases like carbon dioxide.

Carbon dioxide is let of when hydrocarbons burn. There has been an increase of carbon dioxide by 22% and this increase leads to enhancing the greenhouse effect and causes global warming.

When solid particles are released from the burning of fuels then global dimming occours which makes clouds more reflective than normal clouds by water droplets condensing.

When sulphur dioxide burns, sulphuric acid is produced that evapourate but when they condense they cause acid rain which damages buildings and rocks. If reacted with calcium carbonate the products formed are calcium hydroxide and calcium sulphat which are a lot less harmless.

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Better Fuels

Since oil is a non-renwable resource we are slowly running out of it.

Ethanol is a substance found in alchohol and antiseptic liquids and can be made through fermentation. Fermentation is a renewable process.  5% of ethanol in petrol tankers. The complete combustion of ehtanol forms carbon dioxide and water vapour.

A proportion of this carbon dioxide can be made up through the sugar cane grown for fermentation.

Hydrogen can be made through the electrolysis of water which can be used as a renwable feul. When hydrogen is burnt only water vapour is produced so does not cause any pollution. This also produces electricity so can power electric motors.

However, hydrogen is very explosive and is bulky and difficult to store as a gas so it is usually stored as a liquid at high pressure and low temperature.

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