Question

What is a thermos flask?

Answer 1

1. Thermos flask: It is a special type of bottle or flask that keeps hot liquid hot and cold liquids cold for a long time.
2. A thermos flask:
   

Construction of thermos flask:

1. It is a double-walled glass bottle that is kept inside a metal or plastic case.
2. The inner surfaces of both the walls are made shiny or silvery and the air is removed between the walls to create a vacuum.
3. The mouth of the thermos flask is covered by a stopper.

Working of thermos flask:

1. A thermos flask is designed in such a way that it will reduce the loss or gain of heat.
2. The vacuum between the double wall of the flask prevents heat transfer by conduction or convection.
3. Glass is a bad conductor of heat due to which heat neither escapes nor enters the flask.
4. The brightly polished walls prevent any heat gain or loss by radiation.
5. Thus, heat transfer is minimized which helps the thermos flask maintain a constant temperature for a longer duration.