A heater is switched on at floor-level in a cold room. A student notices that the air near the ceiling becomes warm while the air near the floor remains colder. This is due to convection.
Which statement is correct?
Warm air is less dense than cold air so it rises to the ceiling of the room.
Warm air is more dense than cold air so it rises to the ceiling of the room.
The molecules in cold air have more kinetic energy than the molecules in warm air so they sink to the floor of the room faster.
The molecules in warm air are closer together than the molecules in cold air so they rise to the ceiling of the room.
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.