So i believe is exercise:)
1. The correct answer among the choices provided is the third option. Measuring the temperature increase of water from doing work by stirring it is an experiment generally regarded as being first carried out by James Joule.
2. Joule's experiment directly shows that heat is a form of energy. He wanted to make a different way of measuring energy.
Answer: There are 9 molecules.
Explanation: 3H2O has 6 hydrogen atoms and 3 oxygen atoms. Heres a diagram.
HHO + HHO + HHO = 3H2O
A: decreases in specific heat capacity