Name: The Most Important Instrument
Uploaded: 2019-07-19
Duration: 7 min 34 s
Description: The more modern thermometer was invented in 1709 by Daniel Fahrenheit. In this video, we will learn about thermometers and how it is invented and used.

Question

What is the function of a thermos flask, and how does it reduce heat loss?

Accepted Answer

A flask is a glass container used to store or heat liquid substances. Flasks may be flat bottom or round bottom. A round bottom flask is used for gas preparation, where heating is required. Since the flask is round-bottomed, heat is uniformly distributed throughout on heating. A flat bottom flask is used to store a liquid or for gas preparation where heating is not required. A conical flask is used to hold and measure chemical liquid samples and to mix different solutions.

Thermos flask is used to keep a hot liquid hot and a cold liquid cold for a long time. It is a double-walled glass vessel. The outer surface of its inner wall and the inner surface of its outer wall are silvered. The space between the two walls is almost vacuum. The walls are sealed at the top. The flask is placed on a cork, in a metal case and is secured at the neck with a ring of rubber. Heat from a hot liquid in the flask cannot escape from it by conduction or convection as there is vacuum between the two walls. The outer surface of the inner wall, being silvered, is a bad radiator and so it does not radiate heat from the liquid. Conversely, the inner silvered surface of the outer wall checks radiation. The glass is itself a bad conductor of heat. The air, cork and rubber between the flask and the container are also bad conductors of heat. So, they do not allow the heat of the hot liquid contained in the flask to go out by conduction or convection. The cork in the neck of the flask and the cup over that prevents loss of heat by convection.

What is the function of a thermos flask, and how does it reduce heat loss?

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