The Vacuum / Thermos Flask

In order for things to remain at a constant temperature then there needs to be no net transfer of thermal energy. This occurs if the object is at the same temperature as its surroundings, but if one is hotter then we need to limit the 3 methods of thermal energy transfer. One device that does this is the Vacuum or Thermos Flask.

The stopper stops __________ through the pouring hole. It is made of plastic to reduce __________. The inner silvered surface reduces __________. The outer silvered surface reflects back any __________ emitted from the inner surface. The connected double wall means that any heat __________ away by the wall will eventually work its way back. The minimal contact with the outside wall reduces __________. The Vacuum between the walls totally stops __________ and __________.