How does a vacuum flask keep ice cold?
Lastly, conduction occurs when a hot object is placed next to a cold object. The heat is passed from the warmer to the colder object. This is why your hand gets burned when you touch a hot stove. The heat requires a medium to move through. Heat moves through some materials very easily (conductors), and other materials resist the flow of heat (insulators). By having a double-walled glass flask with a vacuum between the layers of glass, there is no medium for the heat to flow through and the ice stays cold.
