Energy Forms and Transfer
Every question in this unit — pendulums, roller coasters, solar heaters, light bulbs — is really asking the same thing: where did the energy start, where did it end up, and how much became unusable heat along the way? Get comfortable tracking energy through a system and Q1 to Q8 stop looking like eight different topics and start looking like one skill applied eight times.
Overview — How This Chapter Fits Together
Energy is measured in joules (J) and comes in recognisable forms — kinetic, gravitational potential, chemical, thermal, and so on. The chapter has one non-negotiable rule underneath everything: energy cannot be created or destroyed, only transformed or transferred. Efficiency, heat transfer, and resource classification are all just consequences of applying that one rule to real devices.
- A transformation changes the form of energy (chemical → electrical). A transfer moves the same form from one place/object to another (heat conducted along a metal rod).
- Real devices always 'waste' some energy — almost always as heat and/or sound — which is why efficiency is never 100%.
- Renewable vs non-renewable is about the rate of replenishment of the source, not how 'clean' it is.
The shape of the chapter
Command terms this topic actually tests
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| State | Give a short, precise answer with no supporting argument. | AO1 | Q1 wants the law in your own words — the core idea ('cannot be created/destroyed, only transformed') must appear; padding without it scores 0/2. |
| Describe | Give a detailed, sequential account of what happens. | AO2 | Q2 needs the sequence GPE → KE with the word 'converted' — naming only the start and end states without the link between them drops a mark. |
| Explain | Give reasons — the mechanism behind an observation. | AO3 | Q3(b)/Q6(b) need the physical mechanism (reflection, friction, particle speed), not a restatement of the observation. |
| Calculate | Produce a numerical answer with working shown. | AO1 | Marks go for formula, correct substitution, AND final answer with unit — a right number with no unit still loses a mark. |
| Identify | Select or name the correct item from given information. | AO1 | Q8(a) wants one word/phrase (the independent variable) — explaining why is a different, separate mark. |
| Compare | State similarities and/or differences, referencing both items. | AO3 | Q7(c) needs both the GPE value and the KE value referenced explicitly, not two separate descriptions. |
Key point
Overview