Substances from Crude Oil

C1.5

What do I need to know?

• Recall how hydrocarbons can be cracked to make smaller more useful molecules.

• Describe some of the properties of alkenes

• Explain how alkenes can be used to synthesise polymers for a wide range of different applications.

Supply and demand

• Oil companies have to balance supply and demand for the different fractions of crude oil.

• For example petrol may be higher in demand than diesel but the oil company may have less of it.

• How can they overcome these problems?

Supply and demand – the options

• Oil companies can make the fraction that is in demand more EXPENSIVE

• Oil companies can lobby the Government to make changes to the system of TAXATION.

• Oil companies can make more of the fraction that is in demand, for example by CRACKING.

Catalytic Cracking• The larger fractions from

crude oil can be of limited value as fuels or as chemical feedstock.

• To make these more useful and therefore more valuable they are split into smaller molecules using a process called CRACKING.

Heat the hydrocarbons

to vaporise

Pass over a hot catalyst OR

Heat to high temperature with steam

Decomposition then occurs

Shorter alkenes and alkanes

formed

Recap - Alkenes

• Alkenes are hydrocarbons with double bonds between carbon atoms.

• One double bond is enough, it does not need to be between every carbon atom.

• Examples are ETHENE and PROPENE

The general formula

CnH2n

Test for Alkenes

• Bromine water is an orangey solution. It is orange because it contains bromine molecules (Br2)

• When you add bromine water to an alkene it turns colourless.

Test for alkenes

Polymerisation

Substances from Crude Oil

What do I need to know?

• Recall the many different uses and applications of polymers

• Describe how a polymer is made from monomers and how to draw monomers and polymers

• Explain the problems that are caused by polymers that are not biodegradeable.

Polymerisation

• In polymerisation many small molecules MONOMERS join together to form a larger molecule POLYMER sometimes containing many thousands of monomers.

Polymerisation

Drawing monomers and polymers

monomermonomer

polymer polymer

Uses of polymers

• Cling film/cellophane• Non stick coating (Teflon) • Tights and clothing (Nylon, Lycra)• Windows and doors (uPVC)• Bottles and food packaging• Waterproof coatings for fabrics (Goretex)• Dental polymers• Wound dressings especially for burns• Hydrogels for use in nappies.• Smart materials such as memory foam.

Waste disposal

• Many polymers are not biodegradeable• This means they are not broken down by

microbes• This can lead to problems with waste

disposal

Remedies

• Plastic bags are being made from polymers and cornstarch so that they break down more easily.

• Biodegradeable plastic plastics are now widely used