Understanding the Mass of a Propane Tank

What happens to the mass of a propane tank when the propane inside goes from liquid to gas?

A. The mass decreases

B. The mass increases

C. The mass stays the same

Answer:

C. The mass stays the same

When a propane tank sits outside with its valve closed, and the propane inside undergoes a phase change from liquid to gas, the mass of the tank remains constant. This is due to the Law of Conservation of Mass, which states that matter cannot be created or destroyed, only transformed.

During the phase change process, while the propane transforms from a liquid to a gas state, the actual particles of the propane are not lost nor gained. The mass of the propane remains the same despite the change in its state from liquid to gas.

Furthermore, since the propane tank is sealed shut, none of the propane gas can escape outside the tank. This means that even though the propane is in the gas phase, all the propane molecules are still contained within the tank. As a result, the overall mass of the tank, including the propane gas inside, does not alter.