Question

State whether given statement is true or false
Cooling of a cup of coffee is an example of thermal equilibrium.
$\left( {\text{A}} \right)$ True
$\left( {\text{B}} \right)$ False

Answer 1

Hint:Thermal equilibrium: When two bodies are brought in thermal contact, heat flows from higher temperatures to the lower temperature and gradually a state occurs where the temperature between the two bodies becomes equal, called a thermal equilibrium state.
-Thermal equilibrium obeys Zeroth law.
-Zeroth law: This law defines that two thermodynamic systems are said to be in thermal equilibrium with a third one, they are in thermal equilibrium with each other.

Complete step-by-step solution:
The thermal equilibrium state attains when the heat energy between the two bodies is the same.

Coffee is at a higher temperature than the surroundings so it will try to attain the thermal equilibrium by transferring its heat energy onto the surroundings.

So, it is not a thermal equilibrium. Coffee has approximately \[{185^0}F{\text{ }}\left( {{{85}^0}C} \right)\] when poured into a cup, it becomes safe to drink after it cools to \[{143^0}F{\text{ }}\left( {{{61.7}^0}C} \right)\].

The hot coffee cools down as heat transfers from the high temperature of the coffee to the less temperature of the surroundings.

The heat is released on a combustion reaction. To keep the Earth’s temperature constant, it is necessary to be in thermal equilibrium.

The greenhouse effect is one of the factors to slow down the heat transfer from Earth to space. Thermal effects are the redistribution of the internal energy in a system.

Hence the correct option is $\left( {\text{B}} \right)$.

Note:
-Thermal equilibrium is a temporally constant state.
-Equilibrium attains in three forms: mechanical equilibrium, chemical equilibrium, thermal equilibrium.
-Thermal equilibrium does not change with time.
-Thermodynamic equilibrium is an axiomatic concept.