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
