Citizen Science #20 by Jamie Zvirzdin
Energy Demystified: Thermal Energy, a Hotbed of Activity
Every Sunday afternoon during the COVID-19 lockdowns, my husband and I met up with our neighbors, Beth and Charlie, for drinks in their back yard. We set up lawn chairs six feet apart and talked about anything and everything in the humid Maryland heat. The tradition continued through the freezing winter, as we donned extra layers of clothing and grasped steaming mugs of wassail and hot toddies. The next year, as sweat again slipped down our necks and condensation off our beers, we made a plan to check an item off Charlie’s bucket list: to go sailing in Greece in August 2024.
Thermal energy was absolutely not on my mind when we made these plans.
In 95-degree temperatures and through Google-issued heat warnings, our sailboat heaved to and fro across the Aegean Sea. On more than one occasion, so did my lunch. We made it back safely and had a marvelous time together, but I learned three things: a) how much I love Greece’s language, history, and food; b) how little our word “nausea” has changed from the original Greek word “nausía” (ναυσία, seasickness); and c) how quickly heat rash and heat exhaustion take the wind out of my sails. Despite how poorly I reacted to both motion and heat, I am still fascinated by how both motion and heat are so intricately connected to thermal energy.
In the world of thermal physics, energy takes on multiple names. Each plays a role in shaping the behavior of matter, and each helps describe specific physical situations. Physicists still argue over naming conventions, but the main players are internal energy (U), work (W), heat (Q), Gibbs free energy (G), Helmholtz free energy (F), enthalpy (H), and calories (kcal). Temperature itself is proportional to the average kinetic energy of the particles in a system, an energy of motion also measured in Joules.
These names, symbols, formulas, and applications may differ, but underneath it all, from a dimensional perspective, they all stem from the same physical quantity: energy. That is, they can all be measured in units of Joules, just like the other flavors of energy we’ve studied this year. Knowing this can help you sort the multilingual alphabet soup that is physics.
Given that Greece, motion, and heat have been so very interconnected for me this summer, let’s nail down these concepts using analogies from Greek mythology. We’ll concentrate on just the first three concepts here, although I hope you’ll explore the others if you like this particular form of energy.
