Organic Chemistry

What is a hydrocarbon?

A compound made of hydrogen and carbon only.

What is the general formula for alkanes?

CₙH₂ₙ₊₂

What is a homologous series?

A group of compounds with:

Same general formula

Similar chemical properties

Gradual change in physical properties

What type of bonds do alkanes have?

Single bonds only.

Are alkanes saturated or unsaturated?

Saturated (no double bonds).

Name the first four alkanes.

Methane, ethane, propane, butane

How do alkanes differ from each other?

By a CH₂ unit.

What is fractional distillation used for?

Separating crude oil into useful fractions.

How does fractional distillation work?

Crude oil is heated → vaporises

Vapours rise through a column

Condense at different temperatures

Why do fractions separate?

They have different boiling points.

What happens to boiling point as chain length increases?

Boiling point increases.

What are short-chain hydrocarbons like?

Low boiling point

More volatile

More flammable

What are long-chain hydrocarbons like?

• High boiling point

• Less flammable

• More viscous

What is complete combustion?

Burning in plenty of oxygen → produces carbon dioxide + water

What is incomplete combustion?

Burning in limited oxygen → produces carbon monoxide + carbon (soot) + water

Why is carbon monoxide dangerous?

It is toxic and can stop oxygen being carried in the blood.