fractional distillation

The strength of the London Dispersion Forces depends on……

the amount of surface contact between molecules
Larger size of molecule=greater surface area=stronger LDF=requires more energy to break=higher melting & boiling points

Physical properties of Hydrocarbons: Physical state

Large hydrocarbon molecules are more attracted (closer) to each other & they tend to be solids, while smaller ones are liquid or gases due to weaker intermolecular forces

Physical properties of Hydrocarbons: Melting & Boiling Points

as the hydrocarbon gets larger, the attraction between molecules becomes stronger. More energy is needed to separate the molecules. As a result, the boiling points increase

• rmr room temp = 25 degrees celcius

Physical properties of Hydrocarbons: Solubility

hydrocarbons have very low solubility in H2O cuz they are non-polar

Distillation is

a process used to separate the various hydrocarbons in a mixture from one another by using differences in boiling points

How does Fractional Distillation work?

1. Crude oil heated to become vapour (350 C)

2. Hot gas enters column moving up- each fraction condenses at a different temperature

3. Liquid collected in trays - high BPs condense on lower trays, low BP condense on higher trays.

4. Trays have valves to allow vapour to bubble through

The most valuable hydrocarbons in petroleum aka crude oil are

C5-12 cuz they are the components of gasoline

Engine Knocking

AKA pinging or detonation, ooccurs when fuel burns hbnevenly in the engine cylinder, the air fuel mizture ignites unevenly and the shocks go off at the wrong time causing a knocking noise and damange to engine cylinder walls and pistons

Cracking

It’s a process used to break down large hydrocarbon molecules into smaller, more desirable ones like high-octane gasoline
- the hydrocarbon chains are heated to a high temp of about 400-500 alongside a catalyst.
- This heating reaction, sped up by the catalyst, breaks the chains down
- it’s an important process cuz it increases the yield of desired products from the same amount
- cracking is also used to break apart larger hydrocarbons like kerosene into smaller ones like ethane & propene (used in plastic production)