Edexcel IGCSE Physics 4.10 Reducing unwanted energy transfer

Practise explaining how lids, insulation, vacuums and shiny surfaces reduce unwanted energy transfer in cups, pools and apparatus.

Exam points

explain how a lid traps air to reduce convection, evaporation or cooling of a hot drink
sketch cooling curves for no lid or insulation, keeping the line above room temperature when needed
link cup or pool-cover features to reduced conduction, convection and infrared radiation

[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 4.10 Reducing unwanted energy transfer 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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4.10 Reducing unwanted energy transfer question 1