Fractional Distillation Simulation — Description & Class Activity
What the Simulation Shows
The 3D interactive models a continuous crude oil refinery fractionating column — the industrial process that separates crude oil into useful products.
Left side — Feed system: A crude oil storage tank feeds into a furnace/pre-heater, which heats the crude to around 350°C. Dark particles flow along the horizontal feed pipe into the base of the column, representing the hot crude oil mixture (C1–C35+) entering as a vapour-liquid mix.
The column — Temperature gradient: The tower runs from 350°C at the base to 25°C at the top, shown as a colour-coded glow inside the glass column (red → amber → yellow → green → blue). This gradient is the engine of separation — vapours rise and cool until they reach their boiling point, then condense.
Particle physics — chain length made visible: Each fraction’s particles are physically sized to their carbon chain length. Large, slow-moving dark blobs (Fuel Oil, C20–C35) barely rise before condensing low. Tiny, fast specks (LPG, C1–C4) shoot straight to the top. Students can see the relationship between molecular size, boiling point, and collection height.
Seven fractions collected:
| Fraction | Chain | Condensation zone |
|---|---|---|
| Refinery Gases (LPG) | C1–C4 | Top — exits as gas |
| Petrol (gasoline) | C5–C10 | Upper column |
| Naphtha | C8–C12 | Mid-upper |
| Kerosene (paraffin) | C11–C15 | Mid column |
| Diesel | C14–C19 | Mid-lower |
| Fuel Oil | C20–C35 | Near base |
| Bitumen | C35+ | Residue — stays in flask |
Labels toggle shows each fraction’s name, carbon chain formula, and a drawn zigzag chain diagram — dual-coded for SEND learners.
Suggested Class Activity — “Chain Detectives”
Suitable for: GCSE Chemistry / Combined Science, Years 10–11 Exam boards: AQA, Edexcel, OCR Gateway, OCR 21st Century, WJEC/Eduqas, CCEA Duration: 20–30 minutes Group size: Individual or pairs
Learning objectives
- Explain how crude oil is separated by fractional distillation
- Describe how boiling point relates to chain length and intermolecular forces
- Identify the main fractions and their uses
Part 1 — Predict (5 min, before opening the simulation)
Give students this prompt before they interact:
“Crude oil is a mixture of hydrocarbons. If you heat it to 350°C and let the vapour rise up a tall tower that gets cooler toward the top — what do you think will happen? Draw a simple tower and predict where you think petrol, kerosene, and LPG would collect.”
Students sketch predictions in their books. No right or wrong yet.
Part 2 — Investigate (10–12 min, using the simulation)
Students open the simulation and work through these questions:
- Set the heater to 100°C. Which fraction(s) are collecting? Why are the others not moving?
- Slowly raise the temperature to 250°C. Watch the column. Describe what changes — use the words rise, condense, boiling point, and chain length.
- Toggle Labels on. Look at the zigzag chain diagrams next to each fraction. What pattern do you notice between the number of carbons and how high up the column each fraction collects?
- Find Diesel and LPG. Compare their particle sizes in the column. Suggest why LPG particles move faster and travel higher.
- Why does Bitumen never leave the flask? What does this tell you about its boiling point?
Part 3 — Explain (5–8 min, written response)
“Using ideas about intermolecular forces, explain why longer hydrocarbon chains condense lower in the column than shorter ones.”
Expected answer (mark scheme language): Longer chains have stronger/greater London dispersion forces (van der Waals forces) between molecules. More energy is needed to overcome these forces, so longer chain hydrocarbons have higher boiling points. They condense (turn back to liquid) at higher temperatures, which occur lower in the column. Shorter chains have weaker intermolecular forces, lower boiling points, and remain as vapour until they reach the cooler upper sections.
Extension / Higher tier
- Why is this process called fractional distillation and not simply distillation?
- The simulation shows a single feed entering at the base. Real refineries use atmospheric and vacuum distillation in sequence — why might a second column operating under reduced pressure be needed?
- Naphtha (C8–C12) overlaps in chain length with both petrol and kerosene. What does this suggest about industrial separation in practice?
Differentiation
- Foundation: Provide a partially completed table of fractions for students to fill in chain length and position during observation
- Higher: Ask students to sketch a boiling point vs. carbon chain length graph from the simulation data and explain the shape
- SEND: Use the ♿ accessibility button — increase text size, toggle an Irlen overlay, switch to Reduce Motion mode, and use keyboard controls (↑/↓) to change temperature gradually