Working of a Thermos 

Thermos is an insulated container with double-wall construction and consists of two air chambers. When the outer chamber of the thermos becomes filled with hot or cold liquid, it pushes against the inner chamber because of the difference in volume between the two chambers. This increases pressure on the inner chamber and reduces pressure on the outer chamber, making it non-porous to external changes in temperature that can cause heat or cold transfer onto food or drink inside it.

Parts of a Thermos

1. Mouth Piece

The mouthpiece is the opening of the thermos through which we pour the liquid. It has a cap attached to it that can be removed to fill it with hot or cold liquid. It has a concave shape that helps in pouring out liquids without any spillage.

2. Bottle

The bottle is the main part of the thermos and contains the liquid after filling it. It is made up of stainless steel.

3. Outer Chamber

The outer chamber has a concave shape and it is the body of the thermos to be precise. The double-walled construction makes this chamber airtight and it does not allow any transfer of heat or cold to take place into or out of this chamber.

4. Inner Chamber

The inner chamber or the interior is located in the middle of the thermos and it has a concave shape. The liquid placed in this chamber will meet no direct contact with the outer chamber. The inner chamber is made up of stainless steel, which provides durability too.

5. Cap

The cap is attached to the mouthpiece of the thermos and it helps in sealing the mouthpiece when not in use. It is used for preventing external disturbances like leakage when there is no liquid present inside. 

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A thermos is a vacuum insulated container used as a vessel for keeping drinks and food hot or cold. It is widely used as an accessory for taking drinks, food and medicines during travels, camping and many other outdoor activities. As far as its mechanism is concerned, its works with vacuum and pressure changes.

Frequently Asked Questions

Q. How long does a thermos keep things hot?

A. Thermoses are a good source to keep the hotness and coldness of food. They are a must for people who like to travel with a cup of coffee or those who like to take food from home to school or office. The average time to which thermos keeps the food or beverage warm or cold is 6 hours. 

Q. Why do thermos flasks stop working?

A. The only reason which thermos flasks stop working is their breakage. Also, they stop their functioning when air gets filled between the two walls of their container. Air eliminates the insulation or heat retention. 

Q. What is the difference between a vacuum flask and a thermos?

A. The main difference between a vacuum flask and a thermos is that a vacuum flask is not completely airtight, while the thermos maintains its air-sealing even when there is no liquid in it. Also, the thermos is small enough to fit in one’s hand, while a vacuum flask looks large.