Final answer:
The water in the beaker cooled to room temperature by transferring its heat energy to the surrounding air, largely through the process of evaporation where the endothermic breaking of hydrogen bonds in the water molecules absorbs heat.
Step-by-step explanation:
The mechanism by which the water in a beaker cools to the same temperature as the air in the laboratory is explained by heat energy being transferred from the water to the air. This is due to the second law of thermodynamics, which states that heat energy will flow from a hotter substance to a cooler one until thermal equilibrium is reached. In this case, the molecules of the water have higher kinetic energy compared to that of the air molecules. As the water and air molecules interact at the interface, this energy is transferred from the water to the air, leading to a decrease in the temperature of the water until it matches the air temperature.
During this process, the hydrogen bonds between water molecules are disrupted, and individual water molecules can escape the liquid through evaporation. Evaporation is an endothermic process, meaning it absorbs heat, which in turn cools the remaining water. This mechanism is similar to how perspiration evaporates from our skin, cooling the body on a hot day due to the energy required to break the hydrogen bonds.