A cup of water is surrounded by air at room temperature. How could you collect evidence to determine whether this system is at equilibrium?

By measuring temperature and looking at the motion of the water in the cup, one can collect evidence to determine whether this system is at equilibrium

Explanation:

For any system to be in equilibrium there must be no transfer of heat and energy or motion between the system and the surrounding environment. If there is no change in the temperature and energy or motion of the cup of water, then it can be said that the system is in equilibrium.