The rate of evaporation in an open system is related to the vapor pressure found in a closed system. When the speed is low, a thin layer, which is almost saturated forms above the earth surface. Water evaporating from lakes, rivers and oceans remains in the atmosphere as vapor, which affects humidity. So the if you measuring the rate at which the mass of water changes over time which is the same as measuring the rate of evaporation , it will be slowed down if fluid is surrounded by more water molecules in the gas state. This lowers the pan evaporation rate.
The amount of minerals dissolved in the liquid Inter-molecular forces The stronger the forces keeping the molecules together in the liquid state, the more energy one must get to escape. As the temperature rises, the kinetic energy of the molecules rises as well. It is a common experience that evaporation is greater in summer and at mid-day than in winter and at night. Because the molecules need a place to escape evaporation can only occur at the surfaces of the fluid that are not in contact with a container, e. Would lowering the pressure or increasing the temperature change the evaporation rate significantly? The exposed surface area is important at determining the rate. At a lower energy only a few molecules possess enough energy to escape from the liquid surface by overcoming molecular attractions.
If you want to speed up the investigation, groups can be assigned different aspects of the investigation and then share their results and conclusions. Allow 2 minutes for evaporation to occur and observe. Three key parts to evaporation are heat, determines the percent humidity , and air movement. As the water evaporates, the partial pressure of water in the gas right over the water will be nearly equal to the vapor pressure, and then it will drop as you go away from the surface, and how steeply this drops which depends on the airflow rate and how long the water has been there evaporating determines the rate at which water will diffuse away. The sun has a major affect on the water cycle. I live at 6000' in a semi-arid climate and would like to know if there is an additive that will slow the rate of evaporation of water.
The equation should work fine for water below the boiling point. However, in using this equation there's one thing you have to be very careful about. Heart rate increasesat high temperatures. This effect will slow the evaporation down quite a a lot because the evaporation rate is proportional to the difference between the vapor pressure and the partial pressure of the substance, and diffusion can only take water away so fast. As the temperature of air is increased, its capacity to hold moisture also increases.
Students, hopefully, will come up with wind, heat, humidity, and the nature of the liquid that is being evaporated. The best way to determine the answer is to perform a simple experiment. Energy is needed to raise water vapor to the clouds and move it by winds. This is because the faster the air moves across the surface of water, the more molecules escape from the liquid so the evaporation rate increases. .
Evaporation depends on how much water or liquid is exposed to the heat. Students will then share their findings with the rest of the class and formulate a hypothesis on conditions affecting evaporation. Add about 250 ml of water to the beaker and place it on a hot plate over medium heat. As water condenses, that leaves a depleted layer behind with less water vapor. Is evaporation only created by heat? Generally, high rates of evaporation occur when the atmosphere is dry, implying low humidity.
If this is the case, then as the temperature increases the mass loss rate decreases. The rate of evaporation is determined daily by recording the depth of water. Only the temperate, and amount of surface area of water will effect the water evaporation rate. What the fluid is comprised of will influence the rate of evaporation as well. Evaporation also depends on relative humidity. Since the kinetic energy of a molecule is proportional to its temperature, evaporation proceeds more quickly at higher temperatures.
On average, only a fraction of the molecules in a liquid have enough heat energy to escape from the liquid. There is a higher capacity to evaporate moisture into the air as the air dries. If the vapor pressure is less than 0. Some time is needed to comprise testable questions regarding evaporation, and then additional time to perform each aspect of the investigations. When water vapor condenses into liquid water it releases energy. The answer depends on a number of parameters: surface area, temperature, wind speed, humidity, etc. High pressure on a water surface reduces the rate of evaporation.
If the intermolecular forces in a liquid are weak, molecules can escape easily from its surface and the rate of evaporation is high. Best on this explanation, it is evident that evaporation rates are high during summer and daytime, as opposed to winter and nighttime. If you are not very careful to replace the lost heat energy during the evaporation, the temperature will go down. D wind speed and turbulent diffusion Atmospheric water vapor vertical transport and horizontal diffusion can speed up the evaporation rate. But I have that book 7th edition and cannot find the equation or derivation.