To evaluate a sustainability proposal, state its aim, give evidence for and against, and reach a conclusion that follows from the evidence. The conclusion should be conditional when the data has gaps.
This lesson belongs to environmental sustainability. It builds on comparing waste-management approaches, where you judged options against each other.
What are the four parts of an evaluation?
Use the same four parts every time and the answer is easier to write.
- Aim. What is the proposal trying to achieve?
- Evidence for. What does the data or science say it will do?
- Limits. What might stop it working, or what is missing?
- Conclusion. Is it worthwhile, and under what condition?
Marks usually sit in parts 2 to 4. A student who only lists benefits has answered half the question.
Worked example: a school rainwater tank
An invented school proposes a rainwater tank to water its garden. The garden needs 15 000 litres of water in a month, and the tank is expected to collect 12 000 litres in that month.
Step 1: state the aim. Reduce the use of treated tap water for the garden.
Step 2: calculate the share covered. 12 000 ÷ 15 000 = 0.8, so the tank supplies 80% of the garden’s need.
Step 3: state the limit. The 12 000 litres assumes an average rainfall month. In a dry month the tank collects less, and the garden needs tap water again.
Step 4: write the conclusion. The proposal is worthwhile because it covers 80% of the need in an average month, but it depends on rainfall, so the school should keep a tap-water backup.
Notice that the conclusion uses the number from step 2 and names the assumption from step 3. A conclusion that ignores both is only an opinion.
The mistake that costs marks
The usual slip is an answer such as “This is a good idea because it saves water and helps the environment”. It has no number, no limit and no condition.
The corrected answer quotes the 80%, names the rainfall assumption and gives a conditional conclusion. Cost is also missing from the data in this example, so a strong answer says that cost was not given and cannot be judged.
Check yourself
Another invented school proposes a tank that collects 9 000 litres in a month for a garden that needs 12 000 litres. Calculate the percentage of the need covered, and write one limit of the proposal.
Answer
9 000 ÷ 12 000 = 0.75, so the tank covers 75% of the garden’s need.
One limit: the 9 000 litres depends on rainfall in that month, so a dry month would leave the garden short and tap water would still be needed. A second acceptable limit is that the cost of the tank was not given.
What to study next
Test the skill on mixed questions in the environmental sustainability practice set. The green technology cluster gives more proposals to evaluate.
If you want a teacher to read your evaluations, see online one-to-one Science tuition. The graph evidence and fair-comparison lab helps when a proposal comes with a chart.