Vacuum (thermos) flask

The vacuum flask is designed to keep the very cold liquid at it low temperature and keep hot liquid at it's high temperature.

The vacuum (thermos) flask has a double walled glass vessel inside, which has:
1) A vacuum between the walls.
2) Two interior facing walls coated with silver.
3) Insulating cork supports at the button.
4) An insulating plastic or cork stopper.

If hot tea or coffee, for example, is poured into the flask, the vacuum prevents heat losses by Conduction and Convection, and the silvery walls minimize losses due to Radiation.

The vacuum flask is used for maintaining temperature of substances constant (keeping hot substances hot and cold substances cold)

Parts Of The Flask And How They Prevent Heat Loss
1) Cork: the cork support and cork lid prevents heat losses by conduction.

2) Vacuum: heat loss by conduction is also prevented by the vacuum within the double wall of the flask.

3) Vacuum: the vacuum between the double wall of the flask also prevents heat loss by Convention.

4) Silver-coated surfaces of the wall of flask: the smooth shiny surface of the flask reflect back the heat that would have been lost through Radiation.