Year 9 Science · Unit 2 · Lesson 15
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Learning Goals
1. Compare thermal cracking with catalytic cracking. Give the temperature range and what helps the bonds break in each.
2. Fill each gap with the product that balances the atoms. Then pick out the alkene in each, and say how its hydrogen count gives it away.
(a) C₁₄H₃₀ → C₁₀H₂₂ + (b) C₈H₁₈ → C₂H₄ +
3. Crude oil is a feedstock as well as a fuel. Trace the steps from crude oil to a polyethylene bag. Name at least two processes and say what each one does.
Scenario: green hydrogen
Companies have proposed using the Pilbara’s strong sunshine to split water by electrolysis, making hydrogen gas to ship to Japan and South Korea in place of liquefied natural gas (LNG, mostly methane). Most hydrogen made today is instead extracted from natural gas, which releases CO₂.
4. Explain why hydrogen made by solar-powered electrolysis is called “green”, while hydrogen extracted from natural gas is not.
5. Hydrogen gas reacts with oxygen gas to form water vapour: write the balanced equation, including states. Compare it with CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) to state one benefit of hydrogen over LNG.
Read the data
| Source | 2019 (%) | 2023 (%) |
|---|---|---|
| Coal | 56 | 46 |
| Natural gas | 20 | 17 |
| Oil | 2 | 2 |
| Renewables (solar, wind, hydro and others) | 21 | 35 |
Source: Australian Energy Statistics (Australian Government), electricity generation by fuel, calendar years. Values are rounded, so a column may not add to exactly 100.
6. By how many percentage points did the renewable share rise from 2019 to 2023? What was the average rise per year?
Rise points
Per year points
7. The Australian Government’s target is 82% renewable electricity by 2030. If the share keeps rising at your average rate from 2023, in about which year would it reach 82%? How many points per year would be needed to reach 82% by 2030?
Year
Needed points/yr
8. Oil made only 2% of Australia’s electricity in both years, yet Australia imports most of the oil it uses. Suggest what that oil is used for, and why the switch to renewable electricity barely changes it.
9. Australia could make all its electricity from renewables one day. Explain why that alone would not end its need for fossil hydrocarbons in manufacturing, such as making plastics.