An ice cube is held at the bottom of a glass test-tube filled with water using a heavy metal gauze. The water near the top of the test-tube is heated until it boils, but the ice at the bottom does not melt.
Which row correctly describes the thermal conductivities of glass and water, and how convection affects the transfer of heat downwards?
| Thermal conductivity of glass | Thermal conductivity of water | Convection currents in the water | |
|---|---|---|---|
| A | poor | poor | transfer heat downwards |
| B | poor | poor | transfer heat upwards |
| C | good | poor | transfer heat upwards |
| D | poor | good | transfer heat downwards |
Glass: poor; Water: poor; Convection: transfer heat downwards
Glass: poor; Water: poor; Convection: transfer heat upwards
Glass: good; Water: poor; Convection: transfer heat upwards
Glass: poor; Water: good; Convection: transfer heat downwards
301 exam-style questions on CIE IGCSE Physics 2.3 Transfer of thermal energy, covering 2.3.1a Thermal conductors and thermal insulators, 2.3.1b Explaining thermal conduction, 2.3.2 Convection, 2.3.3a Thermal radiation, 2.3.3b Surface colour and texture, 2.3.3c Rate of emission and absorption of radiation, and 2.3.4 Consequences of thermal energy transfer. Each one has a worked solution and a mark scheme showing where the marks go.