Aqa Gcse Organic Chemistry

Front 1

Where did crude oil come from?

Back 1

• Found in rocks.

• Formed over millions of years from remains of plankton (sea creatures) which were buried in the mud.

• Crude oil is a finite resource.

Front 2

What is crude oil?

Back 2

• Mixture of hydrocarbons

(Methane has single covalent bonds

Front 3

What are hydrocarbons?

Back 3

Hydrocarbons are molecules made of hydrogen and carbon molecules only

Front 4

Examples of alkanes

Back 4

General formula: Cn H(²n+²)

Methane CH⁴

Ethane C²H⁶

Propane C³H⁸

Butane C⁴H¹⁰

Pentane C⁵H¹¹

Front 5

Structure of Alkanes

Back 5

• saturated hydrocarbons (carbons are fully bonded to hydrogens)

• single (covalent) bonds

• only contain hydrogens and carbons

Hint 5

general formula is Cn H(²n+²)

Front 6

Q: Propane is an alkane with 3 carbon atoms. Draw the structure of propane.

Back 6

Hint 6

MEMORISE THESE!!!

Front 7

Boiling point of hydrocarbons

Back 7

Short chain = lower boiling point

Long chain = higher boiling point

Hint 7

Boiling point: the temperature at which the liquid boils or the gas condenses

Front 8

Volatility of hydrocarbons

Back 8

Short chain = higher volatility

Long chain = lower volatility

Hint 8

Volatility: the tendency to turn into a gas

Front 9

Viscosity of hydrocarbons

Back 9

Short chain = low viscosity = very runny

Long chain = high viscosity = thick

Hint 9

Viscosity: how easily it flows

Front 10

Flammability of hydrocarbons

Back 10

Short chain = higher flammability

Long chain = lower flammability

Hint 10

Flammability: how easily it burns

Front 11

What is cracking?

Back 11

When a large alkane is broken down to produce smaller molecules.

Hint 11

Crackalacka

Front 12

Products of cracking (and what they are used for)

Back 12

Shorter chain alkane > used for fuels eg. in cars.

Alkene

Front 13

Conditions for cracking

Back 13

In catalytic cracking we use heat and a catalyst. The catalyst speeds up the reaction.

In steam cracking, we use heat and steam.

Front 14

Alkenes

Back 14

• Have double carbon bonds.

• Can be used to make polymers and other chemicals.

• Alkenes are more reactive than alkanes.

Front 15

Testing for Alkenes

Back 15

• Use bromine water which is orange.

• Bromine water turns colourless.

Front 16

Q: Cracking equation:

Work out the number of carbon and hydrogen atoms in the second product molecule.

C²⁵H⁵² ---> C²⁰H⁴² + C...H...

Back 16

C²⁵H⁵² ---> C²⁰H⁴² + C⁵H¹⁰

Hint 16

The number of carbon and hydrogen atoms on the right hand side must be the same as the left hand side.

Front 17

Testing for alkanes

Back 17

• Use bromine water which is orange.

• Bromine water stays orange.

Front 18

Combustion of hydrocarbons

Back 18

• Hydrocarbon fuels release energy when combusted.

• During combustion the carbon and hydrogen atoms in the fuel react with oxygen. The carbon and hydrogen are oxidised.

Front 19

Complete combustion

Back 19

• If the oxygen is unlimited, this reaction produces carbon dioxide and water.

• H oxidises = H²O

• C oxidises = CO²

Equation is:

Hydrocarbon + oxygen --> carbon dioxide + water

Hint 19

Plenty of oxygen!!

Front 20

Incomplete combustion

Back 20

• If there is not enough oxygen,

• carbon is released as soot.

Equation is:

Hydrocarbon + oxygen --> carbon monoxide + carbon + water

Front 21

Fractional distillation of crude oil

Back 21

• First, crude oil is heated to a very high temperature which

• causes crude oil to boil.

• All hydrocarbons evaporate and turn into a gas.

• Crude oil vapour is now fed into the fractional distillation column.

• Column hotter on bottom and cooler at the top.

• Hydrocarbon vapour rises up.

• Hydrocarbons condense when they reach their boiling point.

• Liquid fractions are then removed and

• Remainers continue rising until they condense.

Hint 21

Very long chain hydrocarbons have very high boiling points. These are removed at the bottom of the column.

Front 22

Uses of alcohols

Back 22

• Fuels

• Solvents

• Alcoholic drinks

Front 23

What are Alcohols?

Back 23

• A homologous series.

•Same functional group

-OH

Front 24

Making ethanol between steam and ethene

Back 24

C²H⁴(g) + H²O(l) <=> C²H⁵OH(aq)

• Steam

• 300°C - 400°C

• 70 atm

• Catalyst (H³PO⁴)

Hint 24

Advantage: high yield of ethanol

Disadvantage: high temp so uses a lot of energy

Front 25

Making ethanol using fermentation

Back 25

C⁶H¹²O⁶(aq) --> 2C²H⁵OH(aq) + 2CO²(g)

• Sugar solution mixed with yeast.

• 37°C

• Neutral pH

•Yeast

• Must take place in anaerobic conditions (without oxygen)

Hint 25

CO² also produced

Advantages: low temp, less energy. From plants, renewable.