Question

question 19 of 27
what must happen for water to boil at a given pressure?
a. the water must gain thermal energy from its surroundings.
b. the average kinetic energy of the water molecules must decrease.
c. the water molecules must become more orderly.
d. the water must give off thermal energy to its surroundings.

Explanation:

Boiling is a phase - change process from liquid to gas. For water to boil at a given pressure, it needs to absorb heat (thermal energy) from its surroundings. This increases the average kinetic energy of water molecules, allowing them to break free from the liquid - phase intermolecular forces. Options B, C, and D are incorrect as decreasing the average kinetic energy (B), making molecules more orderly (C, which is the opposite of what happens during boiling as gas molecules are more disordered than liquid molecules), and giving off thermal energy (D) do not facilitate boiling.

Answer:

A. The water must gain thermal energy from its surroundings.