Edexcel IGCSE Physics 4.10 Reducing Unwanted Energy Transfer Questions

Compare how cup, pool-cover and food-box features reduce energy loss by conduction, convection, evaporation or radiation, then interpret resulting cooling curves.

Exam points

Explain how a lid traps air to limit convection and evaporation, slowing the cooling of a hot drink.
Sketch water-cooling curves with and without a lid or insulation, keeping the no-lid curve above room temperature.
Explain how vacuum gaps and poor-conducting air, plastic or cardboard reduce conduction through cups or boxes.
Explain how trapped air or a lid limits convection by preventing air movement, including in pool covers and boxes.
Explain why shiny surfaces reduce radiative energy loss by reflecting infrared or emitting less.

[Maximum number: 3]

A student pours a known volume of hot water into a metal container. They place the metal container into an insulated plastic cup containing an equal volume of cold water.

Figure for Question Edexcel IGCSE Physics 4.10 Reducing Unwanted Energy Transfer Questions question 1 — Edexcel IGCSE Physics

The student uses temperature probes to measure the temperatures of both the water in the metal container and the water in the plastic cup.

The het water has an initial temperature of $70^{\circ} \mathrm{C}$ and the cold water has an initial temperature of $5^{\circ} \mathrm{C}$ .

Explain how placing a lid on the plastic cup would affect the results.

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Edexcel IGCSE Physics 4.10 Reducing Unwanted Energy Transfer Questions question 1