Step-by-step explanation:
The kinetic energy of the particles is directly proportional to the temperature.
In the given problem, a balloon is filled with water. It is heated then it begins to expand. As the water gains energy the particles of the water moves more freely inside the balloon. The water inside balloon turns into steam. Then, the particles of the water collide with the walls of the balloon and create pressure on the walls of the balloon.
The volume of the balloon will expand in this case.