C7 Hydrocarbons Flashcards
Crude oil
A fossil fuel
A finite resource
Hydrocarbons
Molecules made from carbon and hydrogen only
Smallest hydrocarbon is methane
Homologous series
All alkanes have the same general formula C2H2n+2
Fractional distillation
The mixture of oils in crude oil separated into fractions
Products from crude oil
Fuel- liquified petroleum gas(LPG), petrol,kerosene, diesel oil, heavy fuel oil
Petrochemicals- solvents, lubricants, polymers, detergents
Separating fractions
A fractional distillation column is used where the top is the coolest
Each oil is separated out at different points as the gases with low boiling points go to the top and heavier gas stay at the bottom
Why can be fractions be separated?
As molecules with larger chains have stronger bonds so have a higher boiling point than molecules in shorter weaker chains
Using fuels
Petrol and diesel in car engines
LPG in camping stoves
Kerosene in aircrafts
Heavy fuel oil in ships
What happens to the boiling point when molecules get larger
The boiling point increases
Larger molecules means
Boiling point and viscosity increases
Flammability decreases
What happens if you burn a hydrocarbon
Water and carbon dioxide are produced
Incomplete combustion
When a fuel burns in a shortage of oxygen
Products are water, carbon monoxide and carbon
Complete combustion
CH4 + 2O2 = CO2 + 2H2O
Carbon and hydrogen in fuels are oxidised
Supply and demand
The solution to the demand for petrol is cracking.
Cracking
Kerosene can be cracked into petrol
Essentially it is using a night temperature and a catalyst to break long molecules into smaller molecules that are in a greater demand. The alkenes produced can also help in the production of many other chemicals
Testing for products of cracking
Bromine water is used to test for alkenes. When solution turns from orange to colourless you know there is an alkene
An alkane however will keep the solution orange as they don’t react
Alkanes and alkenes
Alkanes are far less reactive than alkenes
Alkenes
Another series of hydrocarbons They have a double carbon bond Unsaturated molecules as they contain two fewer hydrogen atoms than the alkane Have the formula CnH2n Generally produce incomplete combustion
Functional groups
Usually attached to the carbon skeleton
For an alkene the double bond breaks and the addition of atoms can be added to either side of the double bond
The alcohol series
Contains functional group OH
Names of alcohols end in ol
Aqueous solutions of ethanol are produced when sugar solutions are fermented using yeast
Methanol, ethanol, propanol and butanol
Are used as fuels and solvents
Dissolve in water to form an neutral solution
React with sodium to produce hydrogen
Burn in air to produce carbon dioxide and water
Can be oxidised to produce carboxylic acids
Making alcohol
Fermentation needs: Water Enzymes from yeast Temp between 25-40 degrees Celsius Absence of oxygen
Carboxylic acids
Contain carbon oxygen and hydrogen but still behave as acids
They dissolve in water to produce acidic solutions
React with carbonates to produce carbon dioxide
Have functional group of COOH
Weak acids so are particularly ionised in water
Polymer
A very big molecule
A very long chain molecule
Molecule made from many small molecules called monomers
Polymerisation
Reaction When many monomers are joined together to make a polymer
Small monomers join together to make polymers
2 ways polymers can be made:
Addition
Condensation
Addition polymers
Uses alkenes that have a double bond and addition can occur across this bond
High pressure and a catalyst
Condensation reactions
Need at least 2 monomers of different functional groups joined together to create a new functional group
When they react they join together and lose small molecules such as water
Single reaction can be used multiple times to form long chains of molecules
Amino acids functional groups
H2N-R-COOH
Polypeptides
Amino acids react by condensation polymerisation to form these bonds
Different amino acids combined make different polypeptides
3 carbohydrates
Starch
Sugar
Cellulose
Carbohydrates
biological compounds made from carbon, hydrogen and oxygen
Monosaccharides
Simple sugars
Glucose and fructose
Polysaccharides
Very long natural polymers
Starch
Cellulose
DNA
2 polymer chains made from monomers called nucleotides joined in the shape of a double helix
Nucleotide
Made from sugar molecule, a phosphate group and a base
4 different bases so 4 different nucleotides
Proteins
Natural polymers made from amino acids
Proteins differ from one another as there are 20 different amino acids arranged in different sequences
