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Environmental science · Grades 7–11

Environmental systems and trade-offs

Compare outcomes with a clear boundary and common unit.

Make a worksheet

Learn the idea

System

Define the area, time and processes included in a comparison.

Trade-off

An option can improve one outcome while worsening another.

Unit

Compare like functions, such as impact per use rather than unlike totals.

Evidence

A label is not a substitute for measured data and stated assumptions.

Worked examples

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

60/30 = 2 units per service.

2

Which comparison is more meaningful?

A common functional basis helps compare alternatives.

Impact per matching service under stated assumptions.

Check your understanding

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

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

  3. Does the label natural prove that a substance is harmless?

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

Answers and marking notes

Answers and marking notes
  1. 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.

  2. 15 kg

    50 − 35 = 15 kg.

  3. No.

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

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.