Year 9 Science · Unit 2 · Lesson 04
Challenge Worksheet
Learning Goals
1. Define lifecycle assessment and list the stages it covers.
Data: lifecycle CO₂ of two cars
A simplified lifecycle model compares two mid-sized cars, each driven 150,000 km. It counts only two stages: making the car and driving it.
| Stage | Petrol car | Electric car, NSW grid power | Electric car, renewable power |
|---|---|---|---|
| Making the car, including any battery (tonnes CO₂) | 7.0 | 11.0 | 11.0 |
| Driving (kg CO₂ per km) | 0.16 | 0.11 | 0.00 |
Assumptions: each car is driven 15,000 km per year, so 150,000 km is about 10 years; petrol car 7 L per 100 km at 2.3 kg CO₂ per litre; electric car 17 kWh per 100 km at about 0.65 kg CO₂ per kWh (NSW grid). Making figures rounded from published estimates.
2. Calculate the total CO₂ (making + driving 150,000 km) for each car, in tonnes. 1 tonne = 1000 kg.
Petrol car t
Electric car, NSW grid t
Electric car, renewable t
3. How many kilometres must the renewable-powered electric car be driven before its total CO₂ drops below the petrol car’s total?
Answer km
4. Read the student’s answer below. Identify three errors in it and write a correct version of each.
A student wrote this answer
“Mining uses up finite minerals, but when they run out we can just make new ones from common materials like oxygen and carbon. Recycling is the most preferred step in the waste hierarchy, but it is not worth doing, because recycling a metal takes more energy than mining it.”
| Error in the answer | Correct version |
|---|---|
5. Claim 1: “Making an electric car releases more CO₂ than a petrol car produces in its first two years of driving.” Claim 2: “An electric car charged from renewable electricity is better for the climate over its lifetime.” Use lifecycle reasoning and your answers to Questions 2 and 3 to explain how both claims can be true. Name one stage the model leaves out and its likely effect.