Instructions: In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant.
Input: A fuel is heated in an oven. Above the oven is a tank of water that is sealed. The tank of water begins to boil above the oven. A the water boils steam is created. The steam is denser than air so it needs a place to go. The steam is forced out of the tank and into a piston. The piston moves up. The valve of the piston closes. The valve on the next piston opens. The steam fills the next piston, driving it up, and the other one down.
Output:
fuel ,water ,steam