Cracking

1. 13/07/2014 Cracking L.O. • I know the conditions required to crack hydrocarbons and what this means and why it is important.

2. Distillation tower pressure Catalytic cracker Heat to vaporise Catalytic Cracking • Large hydrocarbons are broken into smaller molecules using heat and a catalyst. • This process is known as catalytic cracking. • The small molecules produced are then separated by distillation. Smaller molecules Big Molecules Molecules break up

3. Cracking hydrocarbons After distilling crude oil, the oil companies find that they have too many long chain _h__________. Yet the short chain hydrocarbons, like p_____, are in great demand. So scientists have found a way to change the_l_____, less useful molecules into _s________, more useful ones. The reaction is called _c__________. The big molecules are _b_______ down, by heating them as they pass over a _c_______. A catalyst helps to s____ up the reaction. petrol larger smaller cracking broken catalyst speed

4. Octane Heat pressure €€ catalyst hexane ethene + Catalytic Cracking • In the catalytic cracker long chain molecules are split apart or ‘cracked’. An example of such a reaction is: Ethene is used to make plastics Used as a fuel C8H18 C6H14 + C2H4

5. Activity decane H H H H H H H H H H H H H C C C C C C C H H C C C C C Heat pressure H H catalyst H H H H H H H H H H H H H H H H + H C C C C C C H H H H H H ethene octane • Draw out displayed formulae of a pair of products formed by cracking decane How many C’s and H’s left over? molecule name?

6. Cracking in the Laboratory liquid paraffin catalyst ethene gas How could we test for ethene gas? water bath

7. Factors Affecting the Choice of Fossil Fuel fossil natural gas coal Ease of Use Different _____ fuels are suited to different jobs, and sometimes it’s just easier to use one rather than another. For example, its easier to use ______ ____ rather _____ than to power a domestic oven because you can control the heat more easily. The same goes for ______ burners. Bunsen

8. Factors Affecting the Choice of Fossil Fuel greenhouse nitrogen water acid rain 2. Pollution Burning any fossil fuel produces CO2, a __________ gas. Fossil fuels also release _______ oxides and sulphur dioxide when they burn. These dissolve in _____ vapour in the air to produce _______. Alternative methods or generating electricity such as _____, wind, tidal etc. would be preferable. solar

9. Factors Affecting the Choice of Fossil Fuel dangerous expensive 3. Storage Some fuels require specialist storage facilities since they are potentially __________– gas is an obvious example. These facilities can be _________ to build and maintain.

10. Factors Affecting the Choice of Fossil Fuel energy coal 4. Energy Value. This is the amount of _______ a fuel has the potential to generate. Lignite and anthracite are both types of_____, but anthracite has a much higher energy value, i.e. you get much more energy from _______ a tonne of anthracite than a tonne of lignite. burning

11. countries cheaper 5. Cost Although lignite has a lower energy value than anthracite, in some ________ where both are available, lignite is used in coal-fired power stations because it is easier to mine and therefore ________. 6. Availability Power stations need a good ______ of raw fuel. This is why coal fired power stations are built near_________, or have good ________ links if they use imported fuel. source coal mines transport

12. toxic quantities carcinogens 7. Toxicity Certain _____ compounds are produced when a fossil fuel is burned and different fuels produce different _________ of these. For example diesel exhaust fumes contain higher levels of __________ ( compounds that cause cancer) than petrol fumes.