2007-07-09 05:56:21 · 2 answers · asked by stewcat123 1 in Science & Mathematics ➔ Other - Science
A vacuum thermos bottle contains two cups, one inside the other. They are attached to each other only at the top rim, creating an air-tight seal of the space between the cups. All the air is then pumped out of this space, leaving a vacuum (no air).
Heat is conducted through air, so a lack of air greatly slows down heat flow through the walls of the thermos. However, due to radiative heat transfer, the heat transfer is not zero, just greatly reduced. Additionally, there is a small amount of conductive heat transfer through the small portion at the top where the two cups are connected.
These bottles are good for keeping extremely cold things cold for a long time, such as liquid nitrogen. However, they can also be used to keep soup hot for a long time.
2007-07-09 06:02:15 · answer #1 · answered by lithiumdeuteride 7 · 3⤊ 0⤋
Well, in a vacuum , heat can't be transferred by conduction or convection and a coating on the outside of the thermos prevents heat transfer by radition thus being keeping your soup warm
2007-07-09 13:02:29 · answer #2 · answered by Ren B 1 · 1⤊ 0⤋