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Ecosystems & sustainability

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Sample exercises

Grades 7–11 · Ecosystems & sustainability

A fictional process uses 60 energy units for 30 identical services. Find energy per service.

Answer and explanation

2

60/30 = 2 units per service.

Grades 7–11 · Ecosystems & sustainability

Which comparison is more meaningful?

  1. Only two unrelated total numbers.
  2. Impact per matching service under stated assumptions.
  3. The color of the product label.
Answer and explanation

Impact per matching service under stated assumptions.

A common functional basis helps compare alternatives.

Grades 7–11 · Ecosystems & sustainability

Why can a reusable item need several uses before a particular impact becomes lower than a disposable alternative?

Answer and explanation

Its initial production impact may be higher, and use/cleaning impacts accumulate differently.

The break-even point depends on the actual data and chosen impact.

Grades 7–11 · Ecosystems & sustainability

A model reduces waste from 50 to 35 kg. What is the reduction in kilograms?

Answer and explanation

15 kg

50 − 35 = 15 kg.

Grades 7–11 · Ecosystems & sustainability

Does the label natural prove that a substance is harmless?

  1. No.
  2. Only if plant-derived.
  3. Yes, always.
Answer and explanation

No.

Risk depends on substance, exposure and context, not the label alone.

Grades 7–11 · Ecosystems & sustainability

Why should transport and disposal sometimes be included in a comparison?

Answer and explanation

They may contribute impacts outside the production stage.

The chosen boundary can change the conclusion.

Study notes