# Many question about water(condensation evaporation)

• kevin_tee
In summary, when high pressure was applied to water, it reduced to lower pressure and caused water vapor to condense.
kevin_tee
Why water condense when high pressure was applied and reduce to lower pressure?(I observe this when I play with water rocket, when I pump air inside there are no vapor, but after I shoot it, there is vapor coming out.)
Does water condense at 100%< humidity?
Does water vapor condense easier when it is heated? (When I boil water, it seems to condense easier)
Are there water vapor semipermeable membrane? (let air pass through, but water vapor can't.)
How many possible ways to condense water?(cooling etc)

Some of the processes you observed are easy to explain by temperature changes.

So does water vapor condense when it was pressurize and then depressurize?

Because of temperature changes. When you compress the air, it heats up ans starts to cool. When it expands it cools down, but as it lost some of the heat to the surroundings, it now cools down to the temperature that is lower than the initial one - and water vapor becomes saturated. Quite possible in the meantime the air - which, if I understand correctly the situation, was all the time in the contact with water - became saturated to a higher degree, which means condensation even easier.

Thanks for your reply, but I didn't understand "Quite possible in the meantime the air - which, if I understand correctly the situation, was all the time in the contact with water - became saturated to a higher degree, which means condensation even easier." what does that mean? Thanks again.

In a closed vessel air that is above water sooner or later becomes saturated. Even if you don't wait long enough to have the air saturated (relative humidity 100%), it still becomes closer to saturation than the air you started with.

Thank you so much

## 1. What is the difference between evaporation and condensation?

Evaporation is the process in which liquid water turns into water vapor due to heat energy, while condensation is the process in which water vapor turns back into liquid water due to a decrease in temperature.

## 2. Why does condensation occur on some surfaces but not others?

Condensation occurs when the surface temperature is lower than the dew point temperature of the surrounding air. This means that the surface is able to cool the air around it, causing water vapor to turn into liquid water on the surface.

## 3. Can condensation occur without evaporation?

No, evaporation is necessary for condensation to occur. Without evaporation, there would be no water vapor in the air for condensation to take place.

## 4. How does humidity affect the rate of evaporation and condensation?

High humidity levels make it harder for water to evaporate, as the air already contains a lot of water vapor. Low humidity levels, on the other hand, promote evaporation as there is less water vapor in the air to begin with. In terms of condensation, high humidity levels make it easier for water vapor to turn back into liquid water, while low humidity levels make it harder.

## 5. What factors can affect the rate of evaporation and condensation?

The rate of evaporation and condensation can be affected by temperature, humidity, wind speed, and surface area. Higher temperatures, lower humidity, and stronger winds can increase the rate of evaporation, while lower temperatures, higher humidity, and stagnant air can decrease the rate. A larger surface area also allows for more water to be exposed to the air, promoting faster evaporation and condensation.

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