Describe how the thermos keep hot things hot or cold things

Describe how the thermos keep hot things hot or cold things cold and you do not have to tell it which to do. and what steps are taken to minimize the heat transfer?

Solution

A thermoflask is bit like a super insulated jug. Most versions have inner chamber and the outer chamber ( plastics and metals ) separated by two layers of glass and a vaccum in between . The glass usually lined with reflective metal layer. Unbreakable glass do away with the glass . Instead they have two layers of stainless steel with a vaccum and a reflecting layer in between . There is also a tight screw down stopper in the top.

The vaccum prevents conduction while the top stopper prevents the air entering or leaving the flask so convection is not possible, when infrared rays tries to leave the liquid then reflective linings of inner chamber reflects it back .