# Real World Physics Applications – Thermodynamics

There’s something kind of awesome that happens when you realize that things you’ve learned in the classroom might actually have real-world applications.  Like, when you go to a foreign country and can  sort of communicate with the locals because you took Spanish 101.

I was watching Shark Tank recently, and these guys came on with this thing they invented.  I don’t know anything for sure about how it works, but I could make some educated guesses, and I think that looking at their invention is a really interesting way to introduce thermodynamics.

I couldn’t find the clip of them on shark tank, but here’s their kickstarter campaign video, which according to youtube raised \$306k in 37 days!

Anyway, it’s a pretty genius invention and I kind of want one. They’re these big metal things shaped like coffee beans and you put them in your coffee.  They immediately cool it to the perfect (still hot) temperature for drinking, and then keep your coffee at that temperature for several hours.

Being a coffee drinker, extreme appreciater, addict, myself, I was like “wow, that’s genius.”

Here’s my guess at how it works: The inside is some metal that has its melting point at a good temperature for coffee.  When you pour coffee over it, the excess heat goes into melting the metal. (This phase change absorbs energy, (called Joules, hence the name Coffee Joulies.)

Then, as the coffee starts to be cooled by the outside air, the metal inside starts to phase change back, solidifying and transferring heat back to your coffee.  (Phase changes can absorb tons of energy, and they will stay at a constant temperature while they do so.)

So simple!

We could even guess at what metal or material might be inside.  It would be something with a melting point around the perfect coffee drinking temperature.

The National Coffee Association says this temperature is 180-185 Fahrenheit, which is 82-85 Celsius. But, drinks.seriouseats.com says 110-120 is ideal, which is 43-49 C.  Coffee Joulies says they keep your coffee at exactly 140, or 60 C.

Then we can check the melting points on the periodic table. Sodium (Na) is 98 C and Potassium (K) is 63 C, Rubidium is 39 C.  Potassium is basically right on, so it could conceivably be made of that.

I just checked their website for more clues. They call it PCM (for potassium? Maybe it’s a mixture of potassium and something else.) Other than that they don’t say what it is, only that it’s natural, edible, and already found in food (potassium again?)

Anyway, fun mystery, and an awesome invention!  And, a really awesome example of how you can use physics to invent useful things.