Question

How do you know if a gas, based on temperature, is saturated or superheated?

Is it when the given temperature at some point is greater than critical temperature(Tc) its superheated and below it is saturated?

Please use methane properties as an example.

Answer 1

Saturated means a situation in which somethings holding the maximum or threshold quantitity of other thing. In this case, we can say saturation is a point at which methane gas is holding maximum water it can hold at a particular temperature. At this point relative humidity is 100%. But, when temperature is increased the absorption capacity of air will increase. It can now take/hold more water.

The saturated condition can be expressed in terms of the pressure exerted by the water vapour.Water vapour,being a gas exerts its own pressure and thereby contributes to the total pressure of air. In saturated condition, the saturation vapour pressure is identical with the actual pressure of the vapour in the air for a particular temperature.

So, let us asume methane can take maximum x amount of water at 100C. So, when x is achieved at 100C, it is called saturated methane. But, if the temperature is increased to 150C, then it can take 2x amount of maximum water(assume). So at 150C at 2x water, we can call it saturated.

Therefore, solubilty at particular temperature, 100% Humidity and saturated pressure can tell us if a gas is saturated or nott. Temperature alone cannot tell us anything about it.