Water at 20 degrees Celsius is placed on a stove. As the water is heated, thermal energy is absorbed by the water. If the water is heated to a maximum temperature of 80 degrees Celsius, what happens as a result of the increased temperature?

The questions have been asked in several important state and regional science exams in the United States. For example: TAKS-Texas Assessment of Knowledge and Skills, New York State Educational Department Regents exams, California Standards Test, etc.