What is a hydrocarbon made up of
Hydrogen and carbon
Fórmula Methane Ethane Propane Butane
CH4
C2H6
C3H8
C4H10
What is the general formula of alkanes
CnH2n+2
Are alkanes renewable
No. They come from crude oil/fossil fuels, which take millions of years to form and will run out.
Properties of shorter hydrocarbons
Lower boiling point
• More volatile (evaporate easily)
• More flammable
• Less viscous (runny)
Are longer or shorter hydrocarbons better as fuels? Why?
Shorter – they ignite easily and burn more completely.
What happens to crude oil first?
It is heated so it vaporises before entering the fractionating column.
What is the process called? Why is it important?
Fractional distillation – it separates crude oil into useful fractions for fuels, plastics, etc.
Which type comes out the top?
Short-chain hydrocarbons (gases, petrol
Which comes out the bottom
Long-chain hydrocarbons (bitumen, heavy oils).
Combustion of a hydrocarbon
Equation:
Hydrocarbon + Oxygen → Carbon dioxide + Water
Cracking,what is it?
Breaking long-chain hydrocarbons into shorter ones using heat and a catalyst.
Why is cracking important
Produces fuels and alkenes for plastics.
What does cracking make
Alkanes → fuels
• Alkenes → polymers (plastics)
How do you crack?
Catalytic cracking
• Thermal cracking
Why does the line have to be drawn in pencil(chromatography)
Ink would dissolve and move.
Why is the water below the line?
So the samples don’t dissolve straight into the solvent.
What happens if water is above the line?
The spots wash off.
Define pure
One substance only.
Formulation
A mixture designed for a purpose.
How can you tell if a substance is pure?
It has a fixed melting/boiling point.
Test for Chlorine
Bleaches damp blue litmus paper white.
Oxygen
Relights a glowing splint.
Carbon dioxide
Turns limewater cloudy.
