Yes, Heat. And no, I'm not talking about the Robert De Niro/Al Pacino heist film (but hooboy, what a helluva gunfight they had in that movie). No, I'm talking about the thermodynamics concept. Unfortunately, thermodynamics is not commonly understood. It's considered basic knowledge in mechanical and chemical engineering (as well as physics), but from the perspective of your average layperson it seems to fall into the "weird science" category. That's too bad, because unlike arcane quantum physics experiments, thermodynamics is directly applicable to countless everyday situations.
To test your knowledge, I've included a quick ten-question quiz. Some of the questions are easy, and some of the questions are ... not easy. Read each question, and then highlight the hidden text to view the answer:
Is heat a property of matter, or can it exist independently of matter?
Is temperature a property of matter?
Is it possible to build a perpetual motion machine?
Is it possible to make a home heating system that pumps out 30 kW, draws only 8 kW, and doesn't need any fuel?
Air at room temperature feels hotter or cooler depending on whether it's humid, dry, or breezy. Is this effect purely subjective?
Take a wooden bucket and a steel bucket, both at 25° C. Will one of them feel warmer than the other?
Suppose you invent a 60 watt light bulb which is 98% efficient. Approximately how much heat should it generate?
Answer: Roughly 1.2 watts.
Why do those damned chicken pot pies burn your mouth?
Answer: The trick is the pastry shell.
What is the SI unit for energy? Is there an SI unit for entropy?
Answer: The SI unit for energy is the joule. The SI unit for entropy is J/K.
Fire-walkers can walk over hot coals at 400° C without injury. Is this an example of mind over matter?
If you scored poorly (or had to guess), or if you think I might be wrong, then check out the explanations for the answers.
Applications to Sci-Fi
Heat transfer and thermodynamics are broadly applicable in sci-fi. Trekkie pseudoscience often violates the laws of thermodynamics, and heat transfer physics play a part in all of those "energy weapon" analyses.
If you want to discuss sci-fi, either for the purpose of writing it or role-playing it, you can improve your realism by obeying the laws of thermodynamics and heat transfer.
So if you generate energy, you must find a way to dispose of it (that's the chief problem with people who concoct arbitrarily huge energy figures for sci-fi events; they usually can't explain where all of this energy goes afterwards). Try to remember the differences between energy, heat, and temperature. Use the right friggin' units! And last but not least, try to follow the rules of heat transfer, accounting for the effects of geometry and heat transfer modes as well as the effects of thermophysical properties.