Investigate Thermal Energy Transfer Mechanisms Practice Test

A 60°C ceramic mug is left on a desk in a 20°C room. A thermometer shows the mug cools over time while the nearby air warms slightly. In which direction does net thermal energy flow during the first several minutes (before thermal equilibrium)?

A sealed glass aquarium contains air at 20°C. A small electric heater warms the air near the bottom to about 35°C. Over several minutes, smoke introduced near the bottom rises while cooler smoke near the top sinks, forming a circulating loop. Which mechanism best explains the movement that transfers thermal energy through the air in the tank?