Freezing and Boiling water at the same time

In summary, when water is placed in a vacuum and the pressure is decreased, the vapor pressure increases and causes the water to boil. This leads to evaporation, which cools the remaining water. With continued evaporation, the water temperature will drop and eventually reach a temperature suitable for freezing. The cause of the increased vapor pressure is the lowered atmospheric pressure, which allows the water's vapor pressure to "win" and create bubbles at the boiling point. This is possible because at a particular temperature, the vapor pressure is fixed, and by lowering the atmospheric pressure, the vapor pressure is able to overcome it and cause boiling faster.
  • #1
AbsoluteZer0
125
1
Hi,

As I understand, by placing water in a vacuum and decreasing pressure, vapor pressure will subsequently be increased causing the water to boil. The water will then evaporate, which will cool the water that is left behind. Further evaporation over a period of time will drop the water temperature to a level suitable for freezing, and the water will then freeze at the top.

It seems pretty clear-cut, but I am struggling to understand how decreasing atmospheric pressure increases vapor pressure. What is the cause of this?

Thanks,
 
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  • #2
I would not say "decreasing pressure increases pressure". If anything, low pressure means there is a "place" for water vapor, so water will happily boil. This boiling will increase the pressure at the expense of the water internal energy - that's why the water temperature drops down. But: this increased pressure is lower than the initial pressure.
 
  • #3
Hi AbsoluteZer0! :smile:
AbsoluteZer0 said:
… I am struggling to understand how decreasing atmospheric pressure increases vapor pressure.

No it doesn't, the vapour pressure depends only on the temperature of the water …

at a particular temperature, the vapour pressure is fixed.

Lowering the atmospheric pressure simply enables the vapour pressure to "win", see http://en.wikipedia.org/wiki/Boiling
While below the boiling point a liquid evaporates from its surface, at the boiling point vapor bubbles come from the bulk of the liquid. For this to be possible, the vapor pressure must be sufficiently high to win the atmospheric pressure, so that the bubbles can be "inflated".​
 
  • #4
So essentially, when their is less atmospheric pressure it lowers the boiling point of water, so vapor pressure is able to cause boiling faster?
 
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  • #5
AbsoluteZer0 said:
So essentially, when their is less atmospheric pressure it lowers the boiling point of water, so vapor pressure is able to cause boiling faster?

Yes. :smile:
 

What is the phenomenon of freezing and boiling water at the same time?

Freezing and boiling water at the same time is a rare phenomenon in which water exists in both its solid (ice) and gaseous (steam) states simultaneously. This is usually only possible under specific conditions.

What are the conditions necessary for freezing and boiling water at the same time?

The conditions necessary for freezing and boiling water at the same time include a high enough pressure and a low enough temperature. This typically occurs at high altitudes where the atmospheric pressure is lower and the temperature is below freezing.

Is it possible for freezing and boiling water at the same time to occur at sea level?

No, it is not possible for freezing and boiling water at the same time to occur at sea level. The atmospheric pressure at sea level is too high for this phenomenon to occur. However, it is possible to recreate this phenomenon in a laboratory setting using specialized equipment.

How does the water maintain both its solid and gaseous states at the same time?

The water maintains both its solid and gaseous states at the same time due to the balance between the energy needed for boiling and the energy released during freezing. The water molecules on the surface of the ice absorb enough energy from the surrounding environment to change into a gas, while the water molecules on the surface of the gas release enough energy to change into a solid.

What other factors can contribute to the occurrence of freezing and boiling water at the same time?

In addition to high altitude, other factors that can contribute to the occurrence of freezing and boiling water at the same time include a strong heat source, such as a flame, and a container with a small surface area to volume ratio. These factors can help maintain the delicate balance of energy needed for this phenomenon to occur.

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