Water Vapour Pressure

Water vapour pressure is the pressure where vapours of water are in equilibrium pressure with the solid-state. When you raise or keep the pressure the water will be condensed. Water is always in an evaporating state and condensing too. When the surface tension is high at that time you will see that water is sticking to it and does not want to evaporate as well. It is a sign of low pressure of vapour in water.

The water vapour you have already seen at your home too and there is a complete science behind which you will observe mostly during the stored water and boiling water. When small bubbles are stored at a constant state that means it is in equilibrium with the vapour pressure of water.

How things work with vapour pressure

When there is a condensed state at that time the vapour pressure of water is always on dynamic change means due to change in temperature, the water will always have some kind of pressure inside. If you have observed when you leave the water at a normal temperature on the next day you will see a bubble inside the contained water. It means that the vapour pressure is trying to move up and water is losing its quantity as well.

In a solid container when a liquid like water is stored and the container is completely closed at that time molecules are formed in gaseous form or phase. Remember when the container is closed at that time the vapour pressure of water will not affect much. If you raise the temperature of the container and it is completely packed then water may try to fade but it won’t lose its quantity. When you see packed water you will understand that even in sunlight it doesn’t dissolve any water amount because those molecules or gas phase does not let the water fade off.

There is always the movement in phases and when water is at the equilibrium molecule movement between the gas and water does not stop.

At the equilibrium

In equilibrium, there is always the concentration of the molecules when they are in the gaseous phase and the pressure which gas Is building is the vapour pressure of water. When the temperature is high in a solid-state or container you will see those high temperatures will give energy to the liquid and giving the energy to the liquid means giving energy to molecules as well. Here you will understand that Molecules are always having energy but when it is heated they will have more energy to escape the water and turn into a gaseous form.

During humidity, the vapour pressure of water will be at a constant vibrating state and the molecules will collide with each other as per the pressure of the surroundings. This vibration is formed by thermal energy and that energy totally depends on the temperature of the vapour which it is getting from the solid-state as well.

How mathematically water vapour pressure works

Since we know the vapour of water is always in an energetic state it is just that it needs some energy to either charge up the molecule so it can make a gaseous form to leave the medium or it will simply lower the energy according to lower temperature if it is there.

The water Vapour formula is H2O which we have already studied at school. To understand what the Water vapour pressure formula is we have got some different types of formulas:-

According to 

• August equation

P = exp (20.386 – 5132/T)

• Antoine equation,

log 10 P = A – B/C+T

• August-Roche-Magnus equation,

P = 0.61094 (17.625T/T+243.04)

• Tetens equation

P = 0.61078 exp (17.27T / T+ 237.3)

• Buck equation

P = 0.61121 exp ((18.678 – T/234.5) (T/257.14 + T))

Now there are many Water vapour pressure formulas that are available for the use but the thing is understanding the concept that we have already discussed above.  

If you want to know about the Saturation water vapour pressure formula then there is the formula for this too.

RH=pw/ps.

RH means Relative Humidity

pw means Pressure in water

ps means saturation water vapour pressure

The above-given formulas are proven but there is always an error in any formula that can’t always show you accurate results so even if you are using them for your work or research you can surely mention that you have used which formula to justify your result.

Conclusion

Water vapour we are hearing from the past already and how things work we have already discussed above. The complete brief about the water vaporising pressure we have understood already where we got the result that there is water always depended on something to keep its molecule if you say temperature, yes and if you say solid medium then yes.  If you are looking at the result for your research then as per your choice of formula you will surely get the result but accuracy will be in question.