Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: The generation of electricity is critical for the operation of nearly all aspects of modern society. The following diagram illustrates the types of fuels used to generate electrical power in the Unites States. In 2009, almost 45% of the power generated in the U. S. was derived from coal, with natural gas making up another 23% of the total. The third primary source of electrical energy is nuclear power, which accounts for approximately 20% of the total amount generated. All of these fuels give off energy in the form of heat. This heat is used to convert water into steam, which is then used to turn a turbine, thus generating electrical power. Answer: electrical power
A:
This heat is used to convert water into steam, which is then used to turn a turbine, thus generating what?