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Vacuum (absence of matter) is an excellent insulator because matter is the vehicle that carries heat from one place to another. A vacuum flask contains a vacuum-sealed space between the outer and inner walls of the vessel.

Without a vehicle, the heat cannot easily be transferred across the gap between the two walls.

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Q: How does a vacuum flask prevent heat from flowing in or out of it?
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Related questions

How thermos flask prevent loss or gain of heat by?

A vacuum makes a good heat insulator.

Vacuum is mantained in thermos flask?

The vacuum reduce heat loss by conduction and convection.

How is heat transferred away from a vacuum flask?

a vacuum flask is not 100% vacuum. it contains some particles or gas molecules which absorbs a small amount of heat.

What is silvering in a vacuum flask?

There is a silvering in the vacuum flask in order to reduce the loss of heat through the means of radiation.

Why are shiny outer surfaces needed in a vacuum flask?

The outer surfaces do not need to be shiny. The interior ones do, to reflect heat back rather than let the heat pass out of the vacuum flask. The vacuum between the double walls of the flask also reduces heat loss.

Why does the hot tea in a Thermos flask remain hot for a long time?

The Thermos (vacuum) flask has a double skinned glass cylinder inside. Between the two walls of the glass cylinder is a vacuum. The glass cylinder is also silvered on all inner and outer surfaces. Both the vacuum and the silvering help to prevent the rapid cooling of a hot liquid, or the warming of a cold liquid. The vacuum inhibits heat transfer by conduction. The silvering reflects the heat and inhibits the heat escaping from the flask. Thermos (often used for a vacuum flask) is a trade-name.Eventually, as anyone who uses a vacuum flask, the once hot drink will have become cool by the end of the day.

What Are Some Objects That Minimize Heat Transfer?

The vacuum flask otherwise known as a thermos flask

What thermos flask prevent loss or gain of heat by?

Thermos Flask prevent loss or gain of heat by separating the internal layer and the external layer with a vacuum (absence of air molecules). Heat is usually transferred through different media (air molecules and other molecules). Without these media, heat can't pass from one place to another, except for radiation which doesn't need any media (it can travel through vacuum)

What could you heat water in that would retain the heat the longest?

A vacuum would retain the heat best, hence a thermos flask has a vacuum around it =-)

Which form of heat transfer is reduced by the use of vacuum inside a vacuum flask?

The vacuum reduces both conduction and convection.

What Vacuum flask keeps liquid at same temperature?

There is no way to permanently store heat. The most you can expect, from a high-quality vacuum flask, is to keep the liquid cold, or hot, for a fairly long time. But gradually, some heat will seep in, or out, until the temperature in the vacuum flask will be equal to the temperature of the surroundings.

Is vacuum flask an insulater?

It's the vacuum that is maintained between the inner and outer containers of the vacuum flask that is the insulator. Heat is unable to move from the inner container through the vacuum to the outer container which is in contact with the outer world.