Question

how does thermos flask maintain the temperature of liquids kept in it?

Answer 1

hi friend...

A flask or a thermos keeps hot liquids hot and cold liquids cold. In other words, a flask retains the temperature of the liquid that is kept inside the thermos. The basic principle behind the working of a flask is to insulate the substance from the outside air so that no heat transfer takes place. When there is no heat transfer, the temperature of the substance remains the same. Hence there is a need to use insulators inside the thermos.
Both foam and vacuum are good insulators. Though 100% vacuum cannot be achieved, anything achieved quite close to it proves useful. This is because vacuum indicates lack of atoms. Lack of atoms indicates no heat loss due to conduction or convection.

The walls of the flask are designed in such a way to limit the transfer of energy to the outside atmosphere. Inside the thermos, there is glass. There is vacuum around the glass. Since glass is very fragile, it is kept within a plastic or metal case. Since glass reflects infrared radiations, it could cause some heat transfer. That is why the glass is silvered. This is done in order to prevent any infrared radiations. Thus the flask is able to retain the original temperature of the substance that is kept inside for a constant period of time.

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Answer 2

Answer:

The thermos flask is also called an insulated flask. Presence of the vacuum in between the two walls of the flask makes to prevent the flow of heat. As a result, hot liquid kept in the thermos flask does not get cold and cold liquid does not get hot.

Explanation:

• Prevention of heat transfer is the main function of the thermos flask .The thermos flask is the such kind of flask in which the hot liquid will remain hot for a long time and the cold liquids will remain cold for a long time.
• In general, the hot liquid will become cold by liberating their heat to the nearby cold substance. For cold substances, it gains the heat from the nearby object.

• The thermos flask made up of two layers and both layers have some gaps among them. Vacuum between these two layers of thermos flask is the main reason to prevent the heat transfer through convection.

• The glass walls reduces the heat transfer by means of radiation therefore, they are coated with silver. The silver coated surface becomes shiny, therefore it reflects all the heat or radiations.

• Heat does not go inside the wall. The layer of glass wall thermos flask is thin, therefore it prevents the loss of heat by conduction.

Therefore, the thermos flask kept maintain the temperature of liquids.