Organic Chemistry Fundamentals

Hydrocarbons are simple molecules containing only hydrogen and carbon atoms, but they're incredibly important in daily life. The length of their carbon chains completely changes how they behave - shorter chains are runny like petrol, whilst longer chains are thick and sticky like honey.

Alkanes (like methane and ethane) only have single bonds between carbon atoms, making them saturated compounds. Their general formula is CₙH₂ₙ₊₂. Alkenes are different because they contain one C=C double bond, making them unsaturated and much more reactive.

When alkenes undergo addition reactions, their double bond breaks open and new atoms join on. This happens when alkenes react with hydrogen, halogens like bromine, or even with each other to form long polymer chains. You can test for alkenes using orange bromine water - it turns colourless when an alkene is present.

Quick Test Tip: Remember that bromine water changing from orange to colourless is the classic test for alkenes - this comes up frequently in exams!

Cracking is the industrial process that breaks down long, less useful hydrocarbon chains into shorter, more valuable ones. It requires high temperatures and catalysts, and it's essential because short-chain hydrocarbons are in high demand for fuels, whilst long chains have limited uses.