IB DP Physics (2025) A3.7 Energy Density & Sankey Diagrams

IB DP Physics energy density and Sankey diagrams lesson pack, Topic A.3 Work, energy and power, SL and HL, first assessment 2025: Sankey diagrams drawn to scale, the efficiency read off them, and the energy density of fuels. Editable worksheet, 62-slide lesson deck, teacher key, worked solutions and a questions-only assessment, supplied as self-contained HTML plus colour and black-and-white PDF.

What students learn

• Reading a Sankey diagram drawn to scale: the energy or power in each arrow, and the efficiency from the widths.
• Drawing one for a chain of devices, whose overall efficiency is the product of the stages, not 100% minus each loss.
• Energy density as the energy a fuel releases per unit volume, in J m⁻³, told apart from the energy per kilogram by the unit.
• The mass of fuel a device burns to do a given useful work or deliver a given power.

IB skills (Tool 3: Mathematics):

• Construct and use scale diagrams (practised).
• Compare and quote ratios to the nearest order of magnitude (practised).
• Understand direct and inverse proportionality (practised).

What’s included:

• Student Worksheet - 22 pages
• Teacher Key - 34 pages
• Worked Solutions - 23 pages
• Assessment - 15 pages
• Lesson deck - 62 slides

Eight structured questions and five multiple-choice items: 60 marks across 39 parts, and nine figures. Five are Sankey diagrams on a squared grid: students read three and draw two, whose answer layers are stripped from the student copy, not hidden. Your class works five questions, 30 marks, in the lesson, between two opening votes and a multiple-choice exit ticket. The votes are on a gas-fired power station heating a home and an electric car’s battery against petrol. Everything else goes home, including three exam-style questions: a pumped-storage station, a coal-fired power station against a nuclear one, and a hydrogen coach against a diesel one.

The last lesson of the topic: its teacher notes raise all five of the guide’s linking questions for A.3, including its Nature of Science question on conservation laws. Efficiency is used here, not retaught. Worksheet and deck open in any modern browser with nothing to install, and the worksheet is fully editable. SI units, IB notation and IB command terms throughout. Suitable for grades 11-12 (ages 16-19) as a lesson, cover lesson, homework or revision.

Related resources:

• Power and Efficiency, the lesson before this one
• Gravitational and Elastic Potential Energy, where ΔEp = mgΔh is taught
• Adding and Subtracting Vectors, the skill pack that teaches scale diagrams
• Scientific Notation and SI Prefixes, the skill pack on orders of magnitude (free)

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