AQA Trilogy Chemistry - C9 Crude Oil and Fuels

Crude Oil

• a finite resource found in rocks

• a mixture of many different carbon compounds

• formed over millions of years of remains of tiny sea animals and plants that were buried in mud

• layers of rock was laid down on top creating the conditions (high pressure and temp in the absence of oxygen) to make crude oil

Hydrocarbon

• a compound containing only hydrogen and carbon atoms

Alkanes

• saturated hydrocarbons

• all the carbon-carbon bond are single covalent bonds

• CnH(2n+2)

First 4 Alkane Molecules

• MAIDEN - methane

• ERLEGH - ethane

• PUPILS - propane

• are the BEST - butane

Impact of the properties of hydrocarbon depending on chain length of molecule

Fractional Distillation

• crude oil is separated into hydrocarbons with similar boiling points called fractions

Complete Combustion

• fuel + oxygen → carbon dioxide + water (+ energy)

• the carbon and hydrogen in the fuel are oxidised completely when burned like this

Incomplete Combustion

• fuel + oxygen → carbon monoxide + carbon + water (+ energy)

• happens when there is a poor supply of oxygen

Cracking Hydrocarbons

• breaking longer, less useful hydrocarbons into smaller, more useful hydrocarbons

• cracked as thermal decomposition (chemical reaction that happens when a compound breaks down when heated) reactions take place

Alkene

• unsaturated hydrocarbon

• have at least one double bond between their carbon atoms

• C=C

Cracking in a lab

Test for Alkanes and Alkenes

• a positive test for alkenes is that it turns orange bromine water colourless

• alkanes don’t react with bromine water