Topic 7-Organic Chemistry Flashcards
What is a hydrocarbon?
It is any compound formed from carbon and hydrogen atoms only.
What are the first four alkanes?
Methane
Ethane
Propane
Butane
What are alkanes?
The simplest type of hydrocarbon.
What are the properties of short carbon chain hydrocarbons?
It is more runny, less viscous.
It is more volatile meaning it turns into gas at a lower temperature.
The shorter the carbon chain the lower the temperature at which the hydrocarbon vaporises or condenses.
It is also more flammable the shorter the carbon chain.
What happens during the combustion of hydrocarbons?
The hydrocarbons are oxidised.
Why are hydrocarbons used as fuels?
Because of the amount of energy released when they combust completely.
How was crude oil formed?
The remains of plants and animals that died millions of years ago and were buried in mud. With a high temperature and pressure the remains turned into crude oil.
What is crude oil a mixture of?
Different hydrocarbons.
How can crude oil be separated?
By fractional distillation.
Describe how crude oil works?
The oil is heated until most of it is turned into gas. The gases enter a fractioning column.
In the column theres a temperature gradient.
The longer hydrocarbons have high boiling points.They condense back into liquids and drain out the column early on when there near the bottom.
Shorter hydrocarbons have lower boiling points. They condense and drain out much later on mesr the top of the column where its cooler.
You end up with the crude oil mixture separated out into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms so they have similar boiling points.
What is crude oil used for in modern life?
It provides fuel for most modern transport.
What is cracking?
Splitting up long chain hydrocarbons into short chain hydrocarbons.
Why are short chain hydrocarbons better than long chain hydrocarbons?
Short chain hydrocarbons are flammable so make good fuels in high demand however long chain hydrocarbons like tar arent very useful.
What other type of hydrocarbon does cracking produce?
Alkenes.
How does bromine water test for alkenes?
When orange bromine water is added to an alkane no reaction will happen and it will stay bright orange.
If bromine water is added to an alkene a reaction occurs because alkenes are more reactive than alkanes.
This results in a colourless compound being produced and the bromine water is decolourised.
