How does a flask keep hot liquid hot?

Answer 1

There are several types of flasks. They are all containers or vessels, usually designed to carry a liquid and often made of glass. They sometimes have a cap and are narrower at the top, but usually do not have a handle.

The first distinction is flasks that are used in a laboratory. There are several types, including erlenmeyer flasks, florence flasks, round bottom flasks, distilling flasks, volumetric flasks, and others. A description of each one is listed to the left under the Related Questions links.

Another type of flask is instead used to carry alcohol. It is a small container usually shaped to fit in a back pocket. It can hold any liquid but usually was designed for alcohol.

See the Related Questions and Web Links to the left for more information and pictures of different types of flasks.

Answer 2

THE INNER WORKINGS OF A THERMOS FLASK:

One way to build a thermos-like container would be to take a jar and wrap it in, for example, foam insulation. Insulationworks by two principles. First, the plastic in the foam is not a very good heat conductor. Second, the air trapped in the foam is an even worse heat conductor. So conduction has been reduced. Because the air is broken into tiny bubbles, the other thing foam insulation does is largely eliminate convection inside the foam. Heat transfer through foam is therefore pretty small.

It turns out that there is an even better insulator than foam: a vacuum. A vacuum is a lack of atoms. A "perfect vacuum" contains zero atoms. It is nearly impossible to create a perfect vacuum, but you can get close. Without atoms you eliminate conduction and convection completely.

What you find in a thermos is a glass envelope holding a vacuum. Inside a thermos is glass, and around the glass is a vacuum. The glass envelope is fragile, so it is encased in a plastic or metal case. In many thermoses you can actually unscrew and remove this glass envelope.

A thermos then goes one step further. The glass is silvered (like a mirror) to reduce infrared radiation. The combination of a vacuum and the silvering greatly reduces heat transfer by convection, conduction and radiation.

So why do hot things in a thermos ever cool down? There are two paths for heat transfer. The big one is the cap. The other one is the glass, which provides a conduction path at the top of the flask where the inner and outer walls meet. Although heat transfer through these paths is small, it is not zero.

Does the thermos know whether the fluid inside it is hot or cold? No. All the

thermos is doing is limiting heat transfer through the walls of the thermos. That lets the fluid inside the thermos keep its temperature nearly constant for a long period of time (whether the temperature is hot or cold).

Answer 3

They keep hot things hot and cold things cold but how do they know ? The flask is actually two thin walled flasks, one sealed inside the other with a vacuum between them. Heat cannot be tranferred through a vacuum, ergo............

Answer 4

The outside of a flask is silver metal, meaning that it reflects more heat than it absorbs, and also it is and insulator, meaning that it keeps the heat inside the flask. But the inside of a flask is thick black plastic which will absorb heat reflect it from the inside surface of the flask and make it go back into the liquid, this process will keep the liquid hot for as long as it remains in the flask.

Answer 5

There is a thick layer of marshmallow like substance within the casing that helps to insulate and absorb infra red radiation.

Copy and pasted ftw.

Answer 6

a flask is used to store and combine chemicals

Answer 7

The silver on the inside reflects the radiation back into the flask keeping it warm and the vacuum in the middle means no heat can pass through the gap