instruction:
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. 
question:
Fuel produces heat. Water is boiled to make steam. Steam spins turbine. Generator is turned. Makes electricity. Electricity transfers to transformers. Produces the correct voltage. 
answer:
fuel ,heat ,water ,steam ,turbine ,generator ,electricity ,voltage 


question:
Water flows by rocks. Chemicals are in the waters. Chemicals react with rocks. Rocks change to a different kind of rock. Oxygen in the air reacts with rocks. Rocks change to a different kind of rock. 
answer:
water ,rocks ,chemicals ,oxygen 


question:
Coal is crushed. The coal is burned at high temperatures inside a boiler. The heat generated converts water to steam. The steam spins propeller blades in the turbine. The spinning turbine rotates coils in the generator. The rotating coils produce electricity. The electricity can be sent through the power grid. 
answer:

coal ,heat ,water ,stream ,propeller blades ,coils ,electricity