Relationship between humidity and evaporation rate

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relationship between humidity and evaporation rate

Explain the relationship between vapor pressure of water and the capacity of air enough vapor density for the condensation rate to equal the evaporation rate. An inverse relationship between relative humidity and evaporation was eastern wind is dry, thus the change in daily evaporation rate was. The rate of evaporation at a given place is always dependent on the humidity of that So,the pressure difference between the gaseous phase and liquid phase.

In the last section, I asserted something that may have been surprising: Obvious phase changes occur when there's either "net" condensation or "net" evaporation assuming you have some liquid water to begin with.

relationship between humidity and evaporation rate

On the other hand, assuming you have some liquid water present to begin with, "net" evaporation, which means that the evaporation rate exceeds the condensation rate, causes liquid water droplets to shrink or disappear altogetheror puddles on the ground to dry up, etc.

The states of net evaporation and net condensation are extremely important to weather forecasters, because they have implications for cloud and precipitation formation, as well as evaporation of precipitation and subsequent evaporational cooling among other things.

To better understand how net evaporation and net condensation are achieved, we need to understand a bit more about what controls the evaporation rate the number of water molecules evaporating in a given area over a given time period and the condensation rate the number of water vapor molecules condensing into liquid water in a given area over a given time period.

For starters, the bonds that loosely connect water molecules in the liquid phase aren't all that strong, so occasionally, the natural vibration of water molecules breaks these bonds, resulting in evaporation. Of course, as you know, the vibration of molecules depends on temperature: So, that means water temperature is a major controller of the evaporation rate.

Lower water temperatures yield lower evaporation rates, while higher water temperature yield higher evaporation rates. What about the condensation rate? To explore the controllers of the condensation rate, let's perform a little experiment, starting with a closed, empty container filled with dry air no water vapor molecules. Now, let's pour some water into the container and see what happens.

In time, the most energetic water molecules break the molecular bonds with their neighbors and evaporate into the space above the water, gradually increasing the number of water vapor molecules there.

Why Does Humidity & Wind Speed Affect Evaporation? | Sciencing

As time passes and as and more water molecules enter the vapor phase in the space above the water, some water vapor molecules condense back into liquid as they come in contact by chance with the interface between the liquid water and the air above.

An experiment that begins with a container free of water molecules left. In the second step of the experiment water is added to the container, and the water begins to evaporate. At the same time, water molecules in the gas phase are free to condense back into the liquid.

At first, the evaporation rate far exceeds the condensation rate. David Babb Initially, the condensation rate is small because only few water vapor molecules are present, and the probability that any one of them will come in contact with the interface between air and water is low.

In fact, the evaporation rate far exceeds the condensation rate early on net evaporation occurs. But, as time goes on, and net evaporation continues, the air above the water contains an increasing number of water vapor molecules. As the number of water vapor molecules increases, the chance of a water vapor molecule contacting the interface between air and water and condensing back into liquid also increases, which translates to an increase in the condensation rate.

So, as the number of water vapor molecules increases in the air above the water, the condensation rate increases, too. The condensation rate will continue to increase until it matches the evaporation rate, which is a state called equilibrium, meaning the condensation rate equals the evaporation rate. At equilibrium, the temperature of the remaining water on the bottom of the container is lower than the temperature of the water that was present at the start of the experiment.

That's because the most energetic water molecules evaporated, thereby lowering the average kinetic energy in other words, the temperature of the water left behind.

Moreover, the temperature of the remaining water equals the temperature of the "air" above the water. This state of equilibrium, where the condensation rate equals the evaporation rate, is depicted on the left below. In the second phase of the experiment, a container at equilibrium left is heated. When water temperature increases rightthe rate of evaporation also increases. In turn, the amount of water vapor in the "air space" above the water increases.

Eventually, the condensation rate increases and balances the accelerated evaporation rate, reaching a new equilibrium. David Babb If we take our container in equilibrium and increase the temperature depicted on the right abovewhat happens?

relationship between humidity and evaporation rate

The increase in water temperature causes the evaporation rate to increase and, for a time, net evaporation occurs. The amount of humidity in the air directly affects the speed at which water will evaporate.

Water vapor in the air therefore varies significantly by location. Sciencing Video Vault Partial Pressure Partial pressure influences the effects of wind speed and relative humidity on evaporation.

The partial pressure of water in the air relates to the amount of water that is contained in the air. When a water molecule that returned to water replaces a water molecule that evaporated, evaporation stops, regardless of wind or relative humidity. Surface Area and Temperature Temperature and the surface area of the water also influence the effects of wind speed and relative humidity.

How Does Relative Humidity Affect Evaporation?

Water molecules are more exposed to air and more influenced by wind speed and relative humidity, the more a body of water is spread out. Water temperature affects how quickly the water particles move.

A water molecule that is moving very quickly is more likely to burst from the water surface into the air.

  • Evaporation Rates, Condensation Rates, and Relative Humidity

Air, being a gas, expands at higher temperatures.