How does my thermos keep the coffee so hot?

Question

How does my thermos keep the coffee so hot?

Answer 1

It's insulated. Duh! lol

Answer 2

Yes, it's AMAZING

the thermos keeps hot things hot and cold things cold

BUT How does it know?

Answer 3

the insulation inside the thermus keeps the heat from the coffee from escaping

Answer 4

There's an insulating layer of air between the inner and outer sleeves. This slows the dissipation of heat from your coffee.

The Muse

Answer 5

A thermos consists of several layers of insulation, but the most important layer is the vacuum layer. Between the inner flask and the outer shell there is an airtight layer where the air has been pumped out. The less air in that layer, the better the thermos works.

Vacuum does not transfer heat, because there is nothing for the heat to travel in. That way, there is a layer between the content of the thermos and the air around the thermos where there is little physical contact.

Say there's hot cocoa in the thermos. The heat will only escape slowly, because it has a hard time getting through the vacuum. Of course, the vacuum in the vacuum flask is not perfect, so it does contain a little bit of air, and some heat will escape. But it happens much more slowly than if the layer was just insulation or air.

If there's something cold in the thermos, the process works in the opposite direction - the heat from the outside air has trouble getting through the vacuum layer and into the contents of the thermos.