C1a - Making crude oil useful

Question 1

What are hydrocarbons

Answer 1

Molecules containing carbon and hydrogen only

Question 2

What is crude oil

Answer 2

Liquid mixture of many hydrocarbons

Question 3

how is crude oil formed

Answer 3

by the decay + heating + pressurisation of the remains of marine creatures that lived millions of years ago

Question 4

How is crude oil non-renewable

Answer 4

being used up faster than is being formed

Question 5

How is crude oil finite

Answer 5

no longer being made or being made extremely slowly

Question 6

Discuss the problems associated with the finite nature of crude oil(3)

Answer 6

all the readily extractable resources of crude oil will be used up in the future

finding replacements for when oil runs out; alternative renewable energy sources

conflict between making petrochemicals and fuels

Question 7

Describe how fractional distillation separates crude oil into fractions(6)

Answer 7

1. oil is heated and vapourised

2 piped into bottom of fractionating column with temp gradient (cold top, hot bottom)

3. vapours cool as they rise
4. oil contains many different fractions which contain mixtures of hydrocarbons with similar boiling points
5. fractions condense when they reach the part with temperature as low as their boiling point(some leave as gas)
6. fractions with larger molecules: higher intermolecular forces, more energy needed to overcome intermolecular forces, resulting in higher boiling points; condense and leave at bottom of the fractionating column

Question 8

Why can crude oil be seperated using fractional distillation(2)

Answer 8

Hydrocarbons in different fractions have differently sized molecules

Hydrocarbons containing larger molecules have stronger intermolecular forces, so more energy is needed to break these intermolecular bonds, so the boiling point is higher

Question 9

Name the fractions from bottom to top(7)

Answer 9

bitumen, fuel oil, heating oil, diesel oil, paraffin, petrol, LPG

Question 10

What bond/force is broken when crude oil is boiled and what is not? (2)

Answer 10

intermolecular forces between hydrocarbon molecules are broken

covalent bonds within hydrocarbon molecules are not

Question 11

Describe some properties of short chain hydrocarbons (4)

Answer 11

low boiling point

volatile

flammable

low viscosity

Question 12

Describe some properties of long chain hydrocarbons (4)

Answer 12

high boiling point

low volatility

less flammable

viscous

Question 13

Explain some of the potential environmental problems involved in the transportation of crude oil(3)

Answer 13

oil tanker crash/oil rig problems cause oil slicks

oil covers birds’ feathers, can’t fly; stops them being waterproof, water soaks into their feathers, die of cold

detergent used to clean up oil spills, consequently damages wildlife (toxic to marine creatures)

Question 14

Explain in simple terms the political problems associated with the exploitation of crude oi(3)

Answer 14

future supply issues; oil shortage leads to +prices; oil-rich countries may keep it for their own use, rather than selling it

oil-rich countries have +power over other countries, choose who and who not to give oil to, leading to political conflicts, wars

harder for countries without much oil/gas (like UK) to acquire it; we may become dependent on oil and gas from politically unstable countries, which can be cut off at any time

Question 15

Describe cracking(3)

Answer 15

thermal decomposition reaction that:

• converts large useless alkane molecules into smaller alkane and alkene molecules that are more useful
• makes useful alkene molecules that can be used to make polymers

Question 16

What are the benefits of cracking(2)

Answer 16

helps an oil refinery match its supply of useful fractions/products (e.g. petrol) with demand for them

produces alkenes which can be used to make polymers