Re: which material, ceramic, plastic or glass would keep coffee hot the longest

Hi Shannon,

That's a good question, and one that I often ask myself when choosing which coffee cup to use.

Let's get some background info. "Heat" is when the atoms and molecules are vibrating and moving around. The faster they move, the hotter the object. "Temperature" is a measurement of the heat of the object. Hot coffee (or anything else) gets cold because the fast moving atoms bonk into the atoms of the container or the surrounding air, and while the container's atoms or the air's atoms move faster, the coffee molecules end up moving slower.

So what we want for a material that will keep coffee hotter longer is the ability to bounce the coffee molecules back with almost the same speed. Glass, Ceramic, and Plastics are all good for this, because they typically don't have crystal structures that dampen the collisions. Metal isn't so good. Another tactic is to have non-moving air (which is a pretty good insulator) inside the material. So Styrofoam (a plastic with air bubbles) or a vacuum flask (glass surrounding air) work well also. Lastly, thick materials will contain the heat longer, so a thick plastic cup will work better than a thin plastic cup.

I'm sorry, but the short answer to your question is that it depends on what kind of ceramic, plastic, or glass you're using, and what the structure of the cup will be. The good news is that this is really easy to test. Just pour the same amount of hot water into each vessel, and put a thermometer into each of them. See which one stays hotter longer, and you're set. I warn you though. Ten different coffee cups made of different ceramic materials will probably have ten different cooling rates.

So which coffee cup do I use? The pretty one.

I hope this helps!

Jeff Yap
Mad Scientist

References:
University of Illinois Physics Van
Wikipedia - Insulator
Thermal Insulation - Experimental demonstration