C1d,E Making Crude Oil Useful+Polymers

1d,e Making Crude Oil Useful + Making Polymers

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Surfacing Roads

Paraffin

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Crude Oil

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The Alkane and Alkene Hydrocarbon Families

Hydrocarbons are compounds made from ____________ and __________ only.

The 2 families of hydrocarbons that you need to learn about are called the

_______________ and the _______________ (be very careful with your handwriting

and spelling – examiners will not be kind to you!)

The Alkanes

Carbon must always form 4 covalent chemical bonds (you will find out why in another module what covalent bonds are but for now you must just learn this fact and the name of the bonds because it will help you). When we draw and name chemicals we use rules to help us:

1. The name of a molecule with 1 carbon atom has the prefix

____

2 ____

3 ____

4 ____

2. The end of the molecule name tells us which family of chemicals the molecule belongs to

e.g. alkane names end in ane alkene ene

To show how these rules work, consider the first 4 alkanes:

The Alkenes C=C

Alkenes are also hydrocarbons because they are made from hydrogen and

carbon only.

The difference between alkenes and alkanes is that alkenes have a carbon-

carbon double covalent bond, C=C

This makes alkenes more chemically reactive than alkanes e.g. for making

polymers

Using the same 2 rules as before but adding a C=C we can draw and name

the alkenes:

What would be the name and molecular formula of the next alkene in the series?

The Alkynes

You do not need to learn about the alkynes but they have a carbon-carbon triple bond. See if you can use the rules that you have learned to draw and name three alkynes.

If you want a really hard challenge, try writing a general formula for the alkynes.

General formula:

CnH2n

Testing for Alkanes and Alkenes

Alkanes are said to be saturated because their carbon atoms are surrounded

by as many single covalent bonds as possible.

Alkenes have at least one carbon-carbon double covalent bond, C=C, so they

are said to be unsaturated.

For each of the displayed formulae below state whether they are saturated or unsaturated (name the first 2 compounds):

The C=C in alkenes means that alkenes are more reactive and there is a chemical test you must learn that tells us whether we have a saturated hydrocarbon (alkane) or an unsaturated hydrocarbon (alkene).

Testing for unsaturation with bromine water

Saturated(alkanes)

Unsaturated(alkenes, C=C)

Why does the bromine water decolourise?

1. The __________ breaks in the alkene2. The Br-Br bond breaks3. Each bromine atom in the molecule attaches itself to a ______________ carbon

atom

4. As the bromine molecules are used up their brown colour ________________ because the product is colourless.

cyclohexene

Bromine water is a yellow/brown colour

name:saturated?:

Higher

Crude Oil

____________ Fuels are fuels that were made over _________________ of years from dead plants and animals.

There are 3 fossil fuels:1. ________ – made from dead trees

2. ____________ – made from dead sea creatures

3. _____________ - usually found with crude oil

Fossil fuels are ________________ resources. That means that there is a

______________ amount and they will run out.

Fossil fuels are also said to be ___________________. That means that they are being used up faster than they can be made.

Crude Oil

Crude oil is made from many different ________________ mixed together

These fractions are made from chemical compounds called ___________________

Hydrocarbons are compounds made from the elements _________ and ______

only

Hydrocarbons can be different sizes which gives them different boiling points.

This allows us to separate fractions by their different boiling points using

fractional distillation. Large fractions have high boiling points

Separating Crude Oil into fractions by Fractional Distillation

1. The crude oil is heated and _____________

and then fed into the fractionating tower

2. The hot vapours ________ and _________

3. As the fractions cool below their boiling

point they ___________ and are collected as

liquids.

(Note that fractionating towers work 24 hours a day. In industry they call this a continuous process)

See the separate table and learn the properties and uses of the fractions

The Laboratory Fractional Distillation of Crude Oil

In the lab we distil a small amount of crude oil. This is called a ____________

process

1. The hydrocarbon mixture is ______________________

2. When the liquid reaches the boiling point (bpt) of the _____________ fraction

that fraction _______________ then cools and _____________ in the test tube.

3. When all the smallest fraction has been collected the temperature of the

liquid starts to ____________ again. It increases to the bpt of the next largest

fraction which then evaporates. This process continues until all of the

fractions have been collected.

How does fractional distillation work?

1. Covalent bonds between carbon and hydrogen atoms within a hydrocarbon molecule are stronger than the ________________ forces between hydrocarbon molecules

2. During boiling intermolecular forces are ______________

3. Intermolecular forces between large hydrocarbon molecules are ______________ than those between smaller hydrocarbon molecules

4. Hydrocarbons with large molecules have a ________________ boiling temperature than those with smaller molecules

— — — — — —

— — — — — —

— — — — — —

— — — — — —

— — — — — —

HIGHERintermolecular force (between molecules)

covalent bond, C-H

Catalytic Cracking

The fractions produced in fractional distillation have different uses

There is a greater demand for the ______________ fractions e.g. petrol than

we can meet but there is an _____________ of the larger fractions (more than

we can use).

If we ___________ the large hydrocarbons with a ___________ (aluminium oxide,

Al2O3) we can ___________ them into shorter more ____________ hydrocarbons.

Test with bromine waterTo find out if we have made both an alkane and an alkene we can test each

fraction with ____________ water. Alkenes turn bromine water from ________ to

___________

Summary

1. Cracking converts large alkane molecules into smaller __________ and

__________ molecules

2. Cracking makes useful alkene molecules that can be used to make

____________

3. Cracking helps oil refineries match their ______________ of useful products such

as petrol with the __________________ for them (it turns long useless fractions

into shorter more useful ones)

Addition Polymerisation

The molecules in plastics are called _____________ molecules

poly = manymer = partmono = one

Polymers are very ____________ molecules

They are made by adding lots of small molecules together called _____________

The reaction that makes polymers from monomers is called __________________

Polymerisation is a process that needs the following conditions:

1.

2.

What monomers are used to make polymers?

Unsaturated hydrocarbons make good monomers because of their carbon-carbon

double bonds, C=C, so we often use alkene molecules as monomers

e.g. ______________ makes _______________ also known as polythene

Polymers are formed in two steps

1. One bond in the carbon-carbon double bond _____________

2. The molecules join end to end to make a long _______________

Naming polymersFirst write “poly” and then the name of the monomer in brackets afterwards e.g.

ethene poly(ethene)styrene _________________________________ poly(vinyl chloride) PVC

Higher

The ends of the chain are left open to show that more monomers could join on.(This is the only time in chemistry you are allowed to leave a bond unfinished).

Drawing polymersPolymers can be made from hundreds of monomers joined together. It is not necessary to draw every monomer in a polymer chain and instead we draw the _______________

e.g.

ethene

chloroetheneor vinyl chloride

poly(propene)

ALSO

styrene (replace H on ethene with benzene ring, C6H5)

tetrafluoroethene makes PTFE (substitute all 4 H on ethene with F)

n

n