Year 9 Science · Unit 2 · Lesson 12
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Each word is used once. Two words will not be used.
Crude oil is a mixture of hydrocarbons that formed over millions of years from ancient marine organisms. Before it can be used, it must be separated into groups called . The oil is heated and its vapour rises up a tall distillation . Different hydrocarbons have different points, so they condense at different heights. Fractional distillation is a separation: no new substances are made. The lightest fraction, gas, leaves from the very top. Lower down, is collected to fuel trucks and trains. At the very bottom, thick is collected to surface roads.
1. Which property decides the height at which each part of the mixture condenses?
2. Explain why fractional distillation is classified as a physical separation method rather than a chemical one.
Read the data
| Fraction | Carbon atoms per molecule | Boiling range (°C) |
|---|---|---|
| LPG (petroleum gas) | 1–4 | below 40 |
| Petrol | 5–10 | 40–175 |
| Kerosene | 10–16 | 175–250 |
| Diesel | 14–20 | 250–350 |
| Bitumen | 70 or more | above 350 |
Source: typical ranges, as in the lesson’s column diagram. Each refinery sets its exact cut-off temperatures a little differently.
Sort it: above or below kerosene?
Use Table 1. Write each item in the box for where it is collected in the column.
Collected above kerosene
Collected below kerosene
Scenario: a refinery tour
On a tour, students see three outlet pipes on the side of a fractionating column. A sign on each pipe gives the temperature of the column at that height. Each outlet collects the fraction whose boiling range (Table 1) includes that temperature.
3. Use Table 1 to name the fraction collected at each outlet.
| Outlet | Column temperature (°C) | Fraction collected |
|---|---|---|
| P | 300 | |
| Q | 120 | |
| R | 210 |
4. List the outlets P, Q and R in order from the top of the column to the bottom. Explain how you decided.
5. A student says petrol is a single pure compound. Use the petrol row of Table 1 to show that this is wrong.
6. Write a short explanation for a sign at the refinery. It should tell visitors how the fractionating column separates crude oil, and why petrol is collected high up while diesel is collected lower down.