the mass of the water the pressure in the container the total energy of the water the position of the atoms in the container
I gave my students this multiple choice question: In a laboratory, a sealed container with 100 g of steam is cooled until all the steam becomes a liquid. The container is then cooled further until all the water becomes a solid. Which of the following remains constant during both of these changes?

Only one answer is correct among these 4 choices:
- the mass of the water
- the pressure in the container
- the total energy of the water
- the position of the atoms in the container

Could you tell me which one is correct?

the mass of the water