thermoswhy the temperatures of liquids inside thermos are not changing?

Expert Answers
ask996 eNotes educator| Certified Educator

Not much else to say about that, but it does make me curious giorgiana1976. With regard to coolers, would this same theory hold true, and if so, would coolers be able to keep hot things hot? Or would this not work due to the lack of a reflective surface?

litteacher8 eNotes educator| Certified Educator
The temperature does change, but not as much as in a regular cup. The secret is the insulation. It keeps warm foods and liquids warm and cold foods and liquids cold, as long as the thermos is not opened. Pretty cool!
giorgiana1976 | Student

The thermos flask provides thermal insulation because the vacuum created between the 2 thin walls of thermos flask is not a good conductor of  heat.

To increase the insulating effect, the surfaces of thermos flask are coated with refelctive substances, therefore the loss of heat by thermal radiation is eliminated.

Due to this double thin wall vacuum principle, the hot or cold liquids inside thermos flasks are keeping their temperatures for hours.