# Is Vaporization against Archimedes' principle and Newton's laws ?

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Vapor is a is a substance in the gas phase at a temperature lower than its critical temperature. Which means in case of water: small particles of water ( lets say a collection of molecules held together having a mass ) leaves the water surface in to the air.

Archimedes' principle states that the upward buoyant force =  weight of the fluid that the body displaces

So the upward buoyant force on the water particle ( Which is vapor ) = weight of the air it displaces

We know that density of water > density of air.

So weight of the water particle > weight of the air it displaces

Which means weight of the water particle > upward buoyant force on it

So when  you consider the equilibrium of the water particle; it going upwards is against Newton's laws.

Can someone please enlighten me on this ?

Thanks a lot.

Closed as per community consensus as the post is Not graduate-level
asked Aug 1, 2019 1 flag
recategorized Dec 22, 2019

not graduate+ level. Users with 500+ reputation may vote here to close.

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A hot gas is less dense than a cold gas; for example in an ideal gas : $\frac{P}{k_b T}= \rho$ with $\rho$ the density, $P$ the pressure and $T$ the temperature, $k_b$ the Boltzmann constant. That's why even if an undercooled gas of $H_2 0$ particle were to have a lower density, there is still no contradiction between evaporation and gravity.

And this is from wikipedia (https://en.wikipedia.org/wiki/Water_vapor) : "Water vapor is lighter or less dense than dry air. At equivalent temperatures it is buoyant with respect to dry air, whereby the density of dry air at standard temperature and pressure (273.15 K, 101.325 kPa) is 1.27 g/L and water vapor at standard temperature has a vapor pressure of 0.6 kPa and the much lower density of 4.85 mg/L. " And they explain how to get it.

answered Aug 1, 2019 by (20 points)
edited Aug 2, 2019 by JA