Fig. 1 shows a cool box used by a field biologist to carry ice packs and small water samples. The box has a shiny inner lining, a thick foam wall and a tigh...
Question 1 Report
Fig. 1 shows a cool box used by a field biologist to carry ice packs and small water samples. The box has a shiny inner lining, a thick foam wall and a tight lid. At the start, an ice pack is at 0 °C. Several hours later, some ice has melted but the temperature of the ice-water mixture is still 0 °C. The biologist wants to keep the samples cool without using an electrical current from a car battery. Energy enters the box from warmer surroundings.
(a) What energy transfer occurs while the ice melts? [2]
(b) Which feature of the box reduces transfer by radiation? [2]
(c) When the lid is opened often, what energy transfer becomes greater? [2]
Answer Details
- (a) Thermal energy is transferred to the ice [1] as latent heat [1]. It melts the ice without raising the temperature of the ice-water mixture above \(0\,^{\circ}\text{C}\).
- (b) The shiny inner lining [2] reduces transfer by radiation because shiny surfaces are poor absorbers and emitters of infrared radiation.
- (c) Opening the lid increases transfer by convection, as warm air moves into the box [1], and by conduction from warmer air or objects [1].
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