This is my first question in this site. I am referring to this question.The linked question what is the advantage of filling nitrogen in bike tubes over air and I got some answers such as:

The biggest advantage to filling your tires with Nitrogen is consistency.

Air pressure fluctuates based on temperature, whereas Nitrogen fluctuates to a much much lower degree


Nitrogen changes pressure with temperature slightly less than water does

But I want to know the reason. Please help me understand this scientifically.

  • $\begingroup$ I've tidied up your formatting and grammar and subtly changed the title so is poses the question rather than assuming the answer. I hope I haven't blurred your intent. $\endgroup$
    – matt_black
    Jan 3 '14 at 17:24

There can be no scientific explanation, because the argument itself is incorrect.

For the most part air is nitrogen. To be specific, about 80% of dry air is made up from nitrogen. In fact both nitrogen and oxygen, the second major components of air that takes up almost all the other 20%, behave extremely like ideal gas. Pressures of dry air and pure nitrogen gas at different temperatures, from far below freezing point to above boiling point, have indeed been measured to incredibly high accuracy. The difference between these two gases is below 0.1%. In fact, near room temperature, many types of gas are close to ideal gas and have very similar temperature profiles.

I am not sure why people are comparing nitrogen with water in that question thread you mentioned. Water is a minor component of air and its concentration varies so dramatically across places. However, even in a summer day, at the maximum humidity of 100%, the amount of water in the air is only 10% of that of oxygen.

Basically, pressure of nitrogen gas do not fluctuate less with change of temperature compared to normal air.


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