hydrocarbons and crude oil

Question 1

what are hydrocarbons

Answer 1

compounds that contain hydrogen and carbon atoms only.

Question 2

what is crude oil

Answer 2

complex mixture of hydrocarbons (mostly alkanes) and a finite resource that is found in the Earth’s crust

Question 3

what was crude oil made from

Answer 3

the remains of organisms that lived and died millions of years ago- mainly plankton

Question 4

Crude oil is an important source of…

Answer 4

-fuels such as petrol, diesel, kerosene
- solvents
lubricants
detergents

Question 5

what is fractional distillation used for

Answer 5

to separate crude oil into simpler, more useful mixtures

Question 6

how does fractional distillation work

Answer 6

1. heated crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top( temperature gradient) ,
2. vapours from the oil rise through the column
3. vapours condense when they become cool enough
   liquids are led out of the column at different heights

Question 7

Small hydrocarbon molecules features

Answer 7

• weak intermolecular forces so low boiling points
• They do not condense, but leave the column as gases
• flammable
  -less viscous

Question 8

long hydrocarbon molecule features

Answer 8

have stronger intermolecular forces, so they have high boiling points, so they condense back into liquids

• They leave the column as hot liquid bitumen.
• viscous
• less flammable

Question 9

The different, useful mixtures are called

Answer 9

fractions, they are only a part of the crude oil

Question 10

name all the fractions of crude oil

Answer 10

at the top - liquified petroleum gas
petrol- fuel for cars
kerosene- fuel for aircraft
diesel- for cars and trains
heavy fuel oil - for ships and power stations
bitumen- for roads and roofs

Question 11

features of complete combustion

Answer 11

• exothermic
• carbon dioxide and water are produced
• the maximum amount of energy is given out

Question 12

complete combustion equation

Answer 12

hydrocarbon+oxygen –> carbon dioxide+water

Question 13

features of incomplete combustion

Answer 13

• happens when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced.

Less energy is released than during complete combustion.

Question 14

what is cracking

Answer 14

a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules

Question 15

what does cracking produce

Answer 15

alkanes and alkenes

Question 16

example of cracking

Answer 16

hexane (C6H14) = butane C4H10 + ethene C2H4

Question 17

describe the steps of cracking(CATALYTIC)

Answer 17

1. heat long chain hydrocarbons to vaporise them
2. the vapour is then passed over a hot powdered zeolite (aluminium oxide) catalyst
3. the long chain molecules split apart on the surface of the specks of the catalyst

THIS IS CATALYTIC CRACKING

Question 18

describe steam cracking

Answer 18

• you can also crack hydrocarbons if you vaporise them, mix them with steam then heat them to a very high temperature

Question 19

why do we need cracking

Answer 19

It helps to match the supply of fractions with the demand for them.
It produces alkenes, which are useful as feedstock for the petrochemical industry.

• Very often, fractional distillation of crude oil produces more of the larger hydrocarbons than can be sold, and less of the smaller hydrocarbons than customers want.

Smaller hydrocarbons are more useful as fuels than larger hydrocarbons. Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply of fuels is improved. This helps to match supply with demand.