This deep dive covers Deep Dive: What's in Crude Oil? within Crude Oil for GCSE Chemistry. Topic 37: Crude Oil It is section 3 of 13 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 3 of 13
Practice
20 questions
Recall
0 flashcards
🔬 Deep Dive: What's in Crude Oil?
Crude oil is a mixture of hydrocarbons:
- Hydrocarbons = molecules made of hydrogen and carbon ONLY
- Most are alkanes (saturated hydrocarbons with single C-C bonds)
- The mixture contains molecules of many different sizes
- It's a finite resource — once it's gone, it's gone (takes millions of years to form)
How Crude Oil Formed:
- Millions of years ago, tiny sea creatures (plankton) died and sank to the seabed
- Layers of sediment buried them, cutting off oxygen
- Heat and pressure over millions of years converted them to crude oil
- This is why it's called a fossil fuel
Fractional Distillation — The Separation Process:
- Crude oil is heated to about 350°C — everything vaporises
- Hot vapour enters the bottom of a tall fractionating column
- Column is hot at bottom, cool at top (temperature gradient)
- As vapour rises, it cools. When a fraction reaches its boiling point, it condenses
- Different fractions collected at different heights
Why It Works: This is a physical process — no chemical bonds are broken. We're just separating molecules by their boiling points. Larger molecules have higher boiling points (more intermolecular forces to overcome).