Detailed 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. 
Q: Coal is burned at a furnace. The resulting heat energy is used to heat water. The heated water is turned into steam. The steam drives a generator. Electricity is produced. 
A:
coal ,heat energy ,water ,steam ,electricity 