What is the formula of alkanes?
CnH2n+2
What are the first 4 alkanes?
Methane
Ethane
Propane
Butane
What are the properties of a shorter chain?
Less viscous
More flammable
more volatile
What is the equation for combustion?
Hydrocarbon + oxygen —–> carbon dioxide + water
What happens to carbon and hydrogen in combustion?
They are oxidised
How does fractional distillation work?
Oil is heated and turned to gas
Hottest at the bottom
Long chains at the bottom as they have higher boiling points
Shorter chains at the top as they have a lower boiling point
Why are short chains good?
They are flammable so they make good fuels
What is cracking?
Thermal decomposition
How does cracking work?
Heat to vaporise long chain
Vapor passed over hot powdered aluminium oxide catalyst
Long chain split apart on catalyst surface
What is another way of cracking?
Vaporise them
Mix them with steam
Then heat to a very high temperature
What is the general formula for alkenes?
CnH2n
What are the first four alkenes?
Ethene
Propene
Butene
Pentene
What happens if you burn alkenes in the air?
They undergo incomplete combustion
What is the word equation for incomplete combustion of alkenes?
Alkene + oxygen —–> carbon + carbon dioxide + water
What does incomplete combustion result in?
Smokier flame
Less energy being released
What happens in addition reactions of alkenes?
The double carbon bond opens up to leave a single bond and a new atom is added to each carbon
What can be added to alkenes?
Halogens
Hydrogen
Steam
What is the addition of hydrogen known as?
Hydrogenation
What happens in hydrogenation?
Alkene is reacted with hydrogen in the presence of a nickel catalyst
What would be the product of ethene + bromine?
Dibromoethane
What can be used to test for alkenes?
Bromine water
What happens when bromine water is added?
It is first orange then will become colourless when bonds are unsaturated
Forming a dibromo-compound
When steam reacts with alkenes what is the product?
Alcohol
What happens when steam is reacted with alkenes?
Water is added across the double bond and an alcohol is formed
How is steam reacted with alkenes?
In the presence of phosphoric acid (catalyst)
What happens after ethanol is formed?
Mixture is passed over a reactor to condense
Ethanol and water have a higher boiling point so they condense and unreacted ethene is recycled
Alcohol is then purified via fractional distillation
What are polymers?
Long chain molecules made up of many repeating smaller molecules called monomers
What can unsaturated monomer molecules (alkenes) do?
Open up their double bonds and join together to form polymer chains
What is it called when alkenes form polymer chains?
Addition polymerisation
How is addition polymerisation done?
Under pressure and a catalyst
How do you draw a repeating unit?
Replace the double bond with a single bond Add an extra single bond to each carbon Fill the rest up Put a brackets round Put an 'n' outside the brackets
What is the general formula for alcohols?
CnH2n+1OH
What are the four alcohols?
Methanol
Ethanol
Propanol
Butanol
What are the properties of alcohols?
Flammable
Soluble in water
Undergo complete combustion
Why are alcohols used as solvents?
They can dissolve things water can’t dissolve
What can alcohols also be used as?
Fuel
What are the conditions needed for fermentation?
Anaerobic
37degrees
Enzymes fro yeast
Slightly acidic
What are carboxylic acids functional group?
COOH
What are the four carboxylic acids?
Methanoic acid
Ethanoic acid
Propanoic acid
Butanoic acid
What are the properties of carboxylic acids?
Behave as acids
Dissolve in water to produce acidic solutions
React with carbonates to produce CO2
Whats the difference between the structure of alcohols and carboxylic acids?
Carboxylic acids have one more oxygen atom
How could alcohols be turned into carboxylic acids?
Adding oxygen (oxidation) + oxidising agent
What is the equation for reacting carboxylic acids with carbonates?
Ethanoic acid + sodium carbonate —–> sodium ethanoate + carbon dioxide + water
How are esters formed?
From an alcohol and carboxylic acid
What are the equation for esters?
Alcohol + carboxylic acid ——>. ester + water
What type of catalyst is used to make esters?
Acid catalyst eg. sulfuric acid (concentrated)
How is ethyl ethanoate formed?
Ethanoic acid + ethanol ——> Ethyl ethanoate + water
What does condensation polymerisation involve?
Monomer of different functional groups
What happens when a new bond is formed in condensation polymerisation?
A small molecule (water) is lost
Number of types of monomer?
A- one
C- two or one with two functional groups
Number of products?
A- one
C- two (polymer + small molecule)
Functional group involved?
A- carbon double bond
C- two reactive groups on each monomer