The water molecules must have gained more thermal energy while Anh was away from the house.
An increase in the temperature of a body means that the body has gained more energy in the form of heat, also known as thermal energy.
The thermal energy represents the characteristic of a body responsible for its temperature.
An increase in the temperature of the water molecules increases their kinetic energy and, thus, makes the water molecules move around faster than before.
More on thermal energy can be found here: https://brainly.com/question/11278589?referrer=searchResults