GCSE chemistry Unit 1

everything after limestone and atoms in unit 1 GCSE chemistry, not finished yet.

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The blast furnace

The coke is nearly pure carbon. This is for reducing the iron oxide into the iron metal.

Hot air is blasted into the furnace making the coke burn faster than normal and the temp rises to around 1500 degrees.

The coke burns and produces carbon dioxide.

The carbon dioxide reacts with the unburnt coke to produce carbon monoxide.

The carbon monoxide then reduces the iron ore to iron by removing the oxygen.

The iron is molten at this temp and is very dense, so it runs to the bottom of the furnace where its tapped off.

The iron that comes out is Pig iron, which is very brittle.

The main impurity is sillicon dioxide (sand) and this is still solid so will stay mixed in with the iron. The calcium oxide then reacts with the sand to form Slag, which is molten and can be tapped off. This is used for roads and fertiliser.


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Alloys

An alloy is a mixture of 2 or more elements but at least one is a metal.

Steel is a metal alloy of iron and has a carbon percentage of 1.7%, can be made stronger by adding nickel chromium and silicon.

Some alloys have special properties where they can return to their original shape by themselves. These are called smart alloys.

Smart alloys can change shape because of the way the atoms re arrange into different forms at different temperatures.

Iron is soft because its particles have a weak structure, we make it stronger by adding other particles from other atoms that fit into the gaps of the iron particles, which stop it from being able to move as much and makes it stronger.



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Fractional Distillation

This is the production of hydrocarbons in a fractional column.

Refinery gases are in the order; methane, ethane, propane, butane, pentane.

It separates the crude oil by evaporating it at different boiling temps and condensing it back down.

The easier a fraction evaporates the more volatile it is, the smaller the molecules in a fraction, the more volatile and flammable the fraction.

The longer the hydrocarbon chains in a fraction, the more viscous it is. As the molecules get smaller the colour of them becomes lighter.

85% is used for fuel for heating and transport ad 8% is used to make plastics.

Large molecules can be split into smaller molecules by catalytic cracking.

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Burning fuels

Complete combustion

When something burns it combusts. Oxygen is needed for a hydrocarbon fuel to burn completely.

hydrocarbon + oxygen = carbon dioxide + water

Incomplete combustion

If there is not as much oxygen, incomplete combustion takes place. Instead of just producing co2 and water it also creates carbon monoxide and/or carbon (soot). It also releases less energy than complete combustion.

hydrocarbon + oxygen = carbon monoxide + water or carbon

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Cracking

Cracking means breaking big hydrocarbon chains into smaller ones. Most hydrocarbons are called alkanes and are saturated. Others are alkenes and are unsaturated and contain a double bond.

The hydrocarbon molecules are heated until they turn into vapor and then mix with a catalyst. The molcules break apart forming smaller alkanes and alkenes. Alkenes are reactive molecules that are used to make plastics and other chemicals.

when a hydrocarbon chain is cracked it always produces at least one alkane and one alkene.

The double bond means the alkenes have potential to join to other molecules and this makes them reactive.

You can test for alkenes by doing a bromine experiment where if an alkene is present the bromine water becomes colourless as the bromine has reacted with the alkene becoming part of it.



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Polymers

Polymers are very large molecules made when hundreds of monomers join together to form long chains. These monomers are joined by covalent bonding.

Polyethene is a polymer made from ethene.

The process in which polymers are made is called additional polymerisation.

Polymerisation of ethene:

Hydrocarbons flip up/down; double bond is split between the 2 carbons; each bond travels to left/right of the carbon; polymer chain grows; branching occurs if high temps are used.

Uses:

Polythene - clingfilm, water pipes, freezer bags; Nylon - Ropes, fishing nets, fabrics; Polyester - balloons, thread, sails

Polymers have to be incinerated which produces toxic substances, which can be removed from the waste gasses, but the toxic gas must be disposed of carefully.

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Ethanol

You can make ethanol from ethene by adding water (steam) and a catalyst.

Hydration of ethene to ethanol

When ethene and steam are blown over a hot catalyst an additional reaction takes place. The double bond opens up and a water molecule is added. A catalyst is used to speed up the reaction.

Fermentation

If sugar is dissolved in warm water and yeast is added, a reaction called fermentation takes place. The yeast converts the sugar into ethanol.

It can be used as a much cleaner fuel because when burned it only produces carbon dioxide and water.


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Comments

:) PurpleJaguar (: - Team GR

Helpful notes so far...

thanks for them :)

Carys Castro

thankyou, really helpful! :-)

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