When would a cup of hot coffee left on the counter stop transferring heat?
a
When the room temperature air has transferred all of its coldness to the coffee
b
When it has gained all of the air's thermal energy
c
When it has reached the same temperature as the room temperature air
d
When it has lost all of its thermal energy
c. When it has reached the same temperature as the room temperature air.
c
When it has reached the same temperature as the room temperature air
The correct answer is c) When it has reached the same temperature as the room temperature air.
When a cup of hot coffee is left on the counter, it transfers heat to the surrounding environment until it reaches thermal equilibrium. Thermal equilibrium is reached when the coffee and the air around it have the same temperature. At this point, the rate of heat transfer between the coffee and the air is equal, and there is no net transfer of heat.
To determine when the coffee has reached thermal equilibrium, you can use a thermometer to measure its temperature over time. Keep checking the temperature until it stops changing or becomes stable. Once the temperature remains constant and matches the room temperature, you will know that the coffee has stopped transferring heat.