How Does a Thermos Work?

Do you have a thermos? They keep hot drinks hot for hours. They keep cold drinks cold for hours. How do they do it?

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They are made of one bottle inside of another. The air between the bottles is sucked out. This creates a vacuum [space with no matter].

Heat can move through air. But heat cannot move through a vacuum. It is an insulator. The heat stays inside the bottle.

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A thermos keeps drinks cold in the same way. The vacuum does not allow heat to move into the bottle. The heat stays outside. Your drink stays cool.

What Can You Do? How can you use a thermos?

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