Thermos flask in EveryDay Science

Thermos flask is a double-walled bottle with silvering on the inner side of each wall with vacuum in between. Any substance, hot or cold, put inside the flask remains so for a considerable period as there is no exchange of heat due to radiation because of the silvering nor due to conduction or convection. Vacuum is a non-conductor and non-medium. Thermos flask is generally used for preserving hot tea, coffee or ice, cold drinks, etc.