Publish On: 2019-05-15

Andy More

Total Post: 752

Question: Describe the superiority of gas as thermometric substance

Reply On: 2013-10-19

lala singh

Total Post: 22

ANS: Describe the superiority of gas as thermometric substance

A gas possesses following natural advantages over a liquid as a thermometric substance:

(i) The so-called permanent gases (like hydrogen, oxygen, nitrogen and helium) can all be obtained in the pure form and preserve their state of aggregation over an extremely wide range of temperature.

(ii) The expansion of gases is far greater than that of mercury, coefficients of expansion of the principal permanent gases being about 20 times that of mercury. This greatly increases the sensitiveness of the instrument by minimizing, almost eliminating the error due to the expansion of the containing vessel.

(iii) The expansion of all gases is regular so that their behavior is similar at both high and low temperatures. This is surely not the case with mercury or any other liquid.

(iv) Gases are far more sensitive to small changes of temperature in view of their much lower thermal capacity compared to that of liquids.

(v) All gases have the same, or very nearly the same, coefficient of expansion and thus expand equally under similar conditions, leading to an identical scale of temperature over all gas thermometers.

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