Notes

Crude oil - non-renewable (finite) resource formed from the fossilised remains of ancient plankton. found in rocks
made from Hydrocarbons - molecules made up of hydrogen and carbon atoms. size can change its properties



In alkanes, carbon atoms bond to 4 atoms - saturated hydrocarbons (all their bonds w/ other atoms single)
low reactivity, but combust quite well = useful as fuels.
Alkanes have the general formula CnH(2n+2)
E.g. if a hydrocarbon contained 7 carbon atoms, the no. of hydrogen atoms would be (2 x 7) + 2 = 16 =C7H16

Methane (CH4)
Ethane (C2H6)
Propane (C3H8)
Butane (C4H10)

Fractional distillation - separating crude oil into groups (Fractions) of hydrocarbons w/ similar no. of carbon atoms.
. Fractional distillation separates hydrocarbons using their different boiling points. PROCESS:
- evaporate crude oil by heating it - vapour put at bottom of fractionating column and rises upwards
- Long-chain hydrocarbons condense at the bottom (Temp highest) and collected as liquids.
- Short-chain hydrocarbons have lower BPS- pass up column and condense at lower temps near top.
- fractions collected + processed to create : fuel (petrol,diesel) petrochemical industry use sum fractions as feedstock to make solvents, lubricants , detergents

homologous series - family of similar compounds



Hydrocarbons with long chains:
Higher BP
Higher viscosity
Less flammable

Burning with plenty of oxygen
. release of energy.
. oxidation of carbon and hydrogen to create CO2 and water.


Burning w/ lack of oxygen
.carbon monoxide(gas) can be created - 2C + O2 → 2CO - colourless, toxic , odourless

Heavy fractions of crude oil do NOT make good fuels bcuz:
. have high BPs
. Have low volatiliy
. dont ignite easily

Cracking (thermal decomposition reaction )- breaks down long-chain hydrocarbons into shorter-chain molecules that are more useful. 2 types:
- Steam cracking - vapourised heavy hydrocarbons combined w/ steam in high temp env = prods. alkanes + alkenes
- Catalytic cracking - vapourised heavy hydrocarbons passed over top of heated catalyst = prods. alkanes/enes

Uses of Alkenes:
. Starting materials for chemicals like ethanol
.Being combined to make polymers

Alkenes - hydrocarbons w/ functional group C=C. double bond means it has a greater reactivity than alkanes (CnH2n) , involved in addition reactions
. unsaturated hydrocarbons- contain double bond between 2 of their carbon atoms (C=C).

4 shortest alkenes:
. Ethene- C2H4
. Propene- C3H6
. Butene - C4H8
. Pentene - C5H10

Examples of Alkene Addition Reactions
. O2- Ethene (C2H4) + oxygen (O2) → carbon monoxide (CO) + carbon (C) + water (H2O) - bcuz their combustion is incomplete, they burn with smoky flames.
. Alkenes and water - when phosphoric acid present , alcohols cn be formed by reacting alkenes w/ steam - Ethene (C2H4) + steam (H2O) → ethanol (C2H5OH)
. Alkenes + halogens - react w/ bromin water + shaken (sol, orange-brown to colourless) - Ethene (C2H4) (colourless) + bromine (Br2) → dibromoethane (CH2BrCH2Br) (colourless) - effective test for distinguishing between alkenes and alkanes.
. Alkenes and hydrogen - when nickel catalyst present , alkanes formed by combining h2 w/ alkene -Ethene (C2H4) + hydrogen (H2) → ethane (C2H6)

hydrogenation - Adding hydrogen atoms across a carbon-carbon double bond

Alcohols - CnH2n+1OH. functional group - hydroxyl group (-OH).
Complete combustion of methanol = methanol+oxygen→carbon dioxide+water
4 Smallest Alcohols
. methanol - CH3OH.
. ethanol - CH3CH2OH.
. propanol
. butanol

Reactions of Alcohols
. When alcohols react w/ a strong oxidising agent, a carboxylic acid is produced.
. air (and heat) - CO2 and water produced.
. Sodium - hydrogen produced.
. water - dissolve to give neutral solutions.

Fermentation - produces ethanol (key part of alcoholic drinks)
. involves adding yeast to a sugar solution = aqueous solution of ethanol + CO2
conditions for fermentation : temp of 37°C , solution thats slightly acidic ,In the absence of oxygen (anaerobic).

Carboxylic Acids properties:
. Partially ionise in water = weak acids.
. CnH2n+1COOH.
. functional group - carboxyl group (-COOH).

4 smallest alchohols:
. Methanoic acid -HCOOH
. Ethanoic acid - CH3COOH.
. Propanoic acid
. Butanoic acid

Reactions of Carboxylic Acids
. When carboxylic acids react with water, they dissolve to give solutions w/ an acidic pH.
. When carboxylic acids +alcohols react together (using acid catalyst), an ester + water produced E.g. Ethanoic acid + ethanol → ethyl ethanoate + water
. carbonates - salt , CO2 , water

Addition polymerisation- joining of short-chain monomers to prod. one long-chain polymer.
Alkenes - monomers used in addition polymerisation - carbon-carbon double bonds in alkenes can open up to allow multiple alkenes to join together.

Examples of Addition Polymerisation
. poly (Ethene)
. poly (propene)

Condensation polymerisation- joining of monomers w/ 2 functional groups to produce larger polymers
functional groups of amino acids : Amine group (-NH2) ,Carboxyl group (-COOH) E.g. glycine (H2NCH2COOH)
Amino acids can be combined by condensation polymerisation to form a polypeptide and water. peptide slinks

NATURAL OCCURING POLYMERS
1) Proteins
Haemoglobin carries oxygen in the blood.
Antibodies play a crucial role in our immune systems.
Enzymes catalyse biological reactions.

2)DNA (deoxyribonucleic acid) - encodes genetic instructions used in development, functioning and reproduction of living organisms/viruses.
. double helix , nucleotides - Adenine (A) , Thymine (T) ,Cytosine (C) ,Guanine (G)

3) Starch and cellulose - made from monomer sugar (carbohydrtes)
4) proteins - made from monomer amino acids