Question

An appliance used to keep hot liquid hot and cold liquid cold is called a ______________.

Answer 1

1. A Thermos flask is an appliance that is double flashed, and vacuumed from the inside, to prevent heat transfer by conduction, convection, and radiation.
2. Silver lining and vacuum in thermos flask are there to prevent heat loss through radiation.

Hence, an appliance used to keep hot liquid hot and cold liquid cold is called a thermos flask.