C7 Flashcards
What is a hydrocarbon?
a compound made of hydrogen and carbon only
What is crude oil? And where is it found?
A mixture of hydrocarbons found in the Earth’s crust- a finite resource (found in rocks)
What are alkanes?
a homologous series of hydrocarbons
What is the general formula for alkanes?
CnH2n+2
What are the first five alkanes?
methane
ethane
propane
butane
pentane
How can the hydrocarbons in crude oil be separated?
They can be separated into fractions by fractional distillation
What are the uses of these separated hydrocarbons
- LPG: heating and cooking
- petrol: car fuel
- kerosene: jet/plane fuel
- diesel: cars/lorries
- lubricating oil: oil for cars
- fuel oil: fuel for ships and factories
- bitumen: road surfaces
What properties of hydrocarbons change with molecular size?
- boiling point: as the length of the carbon chain increases there is an increase in boiling point
- Viscosity: increases with increasing chain length (higher alkanes are less likely to burn so useful as lubricants etc…)
- Flammability:smaller hydrocarbons are more flammable and easier to ignite than larger molecules
How can hydrocarbons be broken down to produce smaller, more useful molecules?
Cracking - this can be done by catalytic cracking and steam cracking
What is a product of cracking?
Alkenes - (unsaturated hydrocarbons) They are a homologous series of hydrocarbons with at least one double bond between two of the carbons General formula: CnH2n
Why do alkenes tend to burn in air with smoky flames?
Due to incomplete combustion
What are the first 4 alkenes?
ethene
propene
butene
pentane
What is the test for the presence of an alkene?
The bromine water test
(orange bromine water turns colourless)
Which are more reactive: alkanes or alkenes?
Alkenes are more reactive due to the presence of the carbon double bond
What is the general formula for alkenes?
CnH2n
What is the functional group and general formula of alcohols?
functional group- OH
formula: CnH(2n+1)OH
How are alcohols formed?
reacting alkenes with water
What are the first four alcohols?
methanol
ethanol
propanol
butanol
Give properties of alcohols
• flammable
• soluble
• can be oxidised to form carboxylic acids
What are some uses of alcohols?
- fuels
- solvents
- methylated spirit- unfit for human consumption
How are carboxylic acids formed? what is the functional group?
functional group: COOH
- oxidation of alcohols
How are esters formed? What is the functional group?
functional group: COO
- carboxylic acid + alcohol (and acid catalyst)
- water is a by-product
What are properties of esters?
- naturally pleasant smells
- volatile
Give examples of natural occurring polymers
- DNA
- polypeptides
- carbohydrates
