A student calculates using the mass of an iron pot and a tub of room temperature water: after using the iron pot on a stove and submerging it in the tub of water, thermal equillibrium should be reached at 40 C. When the student tries this experiment in real life, they can see and hear some of the water boiling as the pot is submerged in water. The final temperature reached is 35 C. Explain why the calculation does not describe the actual result.