lesson
Count impacts beyond the moment of use
1 · Learn
A life-cycle assessment considers raw materials, manufacture, transport, use and disposal or recycling. A product that performs well in one stage can have significant impacts elsewhere. The comparison depends on boundaries and assumptions.
Recyclable does not mean every item is actually recycled or that recycling has no cost. State collection, processing and replacement assumptions rather than declaring one material universally best.
2 · Worked example
A reusable container may require more resources to manufacture but spread that impact across many uses. The number of uses and cleaning assumptions affect the comparison.
3 · Your turn
Why must the assumed number of uses be stated when comparing reusable and single-use containers?
Check your answer
It changes how manufacturing and use impacts are distributed across the service provided.
4 · Apply your learning
Evaluate two fictional lifecycle tables and identify an assumption that could change the conclusion.
Adult guidance and safety
Use supplied evidence and approved models. Practical work needs qualified supervision, risk assessment and suitable equipment. No independent chemical, mains-electricity, radiation or biological-culture experiments. Human biology is general education, not personal medical advice; do not request intimate or health disclosures.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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Follow your teacher's approved method and safety instructions. Record the sample or supplied dataset, conditions, measurements with units and uncertainties where appropriate. Distinguish observations from explanations. A described experiment is not permission to carry it out; do not improvise equipment or invent missing results.
Ask your teacher for support with the method and recording. A prediction is what you think might happen; an observation is what you actually see, hear or feel safely.
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