The factors that cause water to evaporate are:
1. Solar radiation
Solar radiation directly provides the energy necessary for evaporation, in particular for the evaporation of water. used for evaporation. Therefore, solar radiation is the main factor affecting evaporation. Solar radiation undergoes diurnal, seasonal and interannual changes, and water evaporation will also change accordingly with these changes.
2. Temperature
As the temperature of water increases, the speed at which water molecules move increases, making it easier for water to escape. The surface area will increase as the water surface temperature increases. The main factor that directly affects water temperature is air temperature, so changes in air temperature will affect changes in evaporation from the water surface. However, due toComplex factors that affect water surface evaporation, temperature changes are sometimes not very consistent with water surface evaporation patterns.
3. Humidity
The humidity of the atmosphere above the water surface increases, the number of water vapor molecules in it increases, and the vapor pressure difference of saturated water decreases. difference in water vapor pressure between the water surface and the atmosphere, the smaller the difference in water vapor pressure between the water surface and the atmosphere, the slower it escapes from the water surface. Thus, under the same conditions, the lower the air humidity, the greater the evaporation from the water surface. At the same time, changes in humidity are also closely related to temperature.
4. Water vapor pressure difference
Water vapor pressure difference refers to the ddifference between the water vapor pressure at the water surface and the atmospheric water vapor pressure at a certain height above the water surface. Generally speaking, the higher the air density, the higher the number of water vapor molecules per unit volume and, conversely, the lower the water vapor pressure. . The higher the water vapor pressure of the atmosphere, the lower the difference in water vapor pressure between the water surface and the atmosphere and the lower the evaporation from the water surface is basically consistent with the impact of humidity changes on evaporation.
5. Wind speed
Wind can strengthen convection and exchange between air, so that water vapor molecules above the water surface are continuously carried away, ensuring as well as a certain amount of water vapor is always held between the evaporating surface and the sky above. The pressure difference allows evaporation to continue. Within a certain range, the greater the wind speed and the faster the airflow, the more convection and exchange of water vapor in the air, thereby increasing the pressure difference of water vapor at the water vapor interface, which is more conducive to evaporation from the water surface.
But when the wind speed reaches a certain level, the water surface evaporation tends to be stable, and the impact is relatively small at that time. At the same time, when cold air arrives, the increase in wind speed not only will not promote the evaporation of the water surface, but will also reduce evaporation and even cause condensation.
Detailed information:
The principle of evaporation:
Becausethat the molecules in the liquid are constantly The earth is moving irregularly and their average kinetic energy is matched to the temperature of the liquid itself. Due to the irregular motion and collisions of molecules, some molecules always have a higher kinetic energy than the average kinetic energy at any time.
These have sufficient If molecules with sufficiently large kinetic energy are found near the surface of the liquid and their kinetic energy is greater than the work required to overcome the gravitational force between the molecules of the liquid when they fly away, these molecules can break away from the surface of the liquid and fly. outside, becoming the liquid. Molecules that fly away may return to the surface of the liquid or enter the liquid after colliding with other molecules. If more molecules fly out than return, the liquid evaporates.
DifferentAll liquids with the same other conditions evaporate at different rates. This is due to the different cohesive forces between liquid molecules. For example, the cohesive force between mercury molecules is very strong and only a very small number of molecules with sufficient kinetic energy can escape from the liquid surface. This type of liquid evaporates extremely slowly. In other liquids, such as ether, the cohesive force between molecules is very weak and the number of molecules that can escape from the surface of the liquid is greater, so they evaporate quickly.
Baidu Encyclopedia - Evaporation from the water surface
Baidu Encyclopedia - Evaporation (atmospheric physics terms)
Please explain the essential difference between the following changes from the point of view of molecules and atoms: water is broken down by electricity and l'water evaporates when heated
The principle of water evaporation is that the water molecules are at different temperatures (i.e. the energy average molecular kinetics is different). The kinetic energy of individual molecules is different, which constitutes a distribution. The speed can be high or low. If high-speed molecules are on the surface, they can break apart. away from the intermolecular force and run outward, forming evaporation. This evaporation occurs very quickly, but the higher the temperature, the higher the average kinetic energy of the molecules and the higher the ratio of high-velocity molecules. Thus, evaporation becomes more and more evident. When the boiling point is reached, a large number of bubbles that evaporate the internal molecules can race to the surface to evaporate. This forms violent evaporation - boiling.
Whatis the electronic formula for water?
Evaporation of water is a physical change and is the result of the movement of water molecules themselves. The water molecules themselves do not change, but. the distance between water molecules changes.
The electrolysis of water is a chemical change. The molecules themselves change. Water molecules split into hydrogen atoms and oxygen atoms, and then the hydrogen atoms and oxygen atoms recombine to form hydrogen molecules and oxygen molecules. a large number of The fact that hydrogen molecules and oxygen molecules aggregate into hydrogen gas and oxygen gas, respectively, shows that the molecules can be subdivided.
So the answer is: when water evaporates, the water molecules themselves do not change, but the distance between the molecules increases, which is a physical change; when water is electrolyzed, the moleculesof water become hydrogen molecules; and oxygen molecules, which are a chemical change.
The electronic formula of H?O is shown in the figure below:
Water (chemical formula: H?O) is an inorganic substance composed of two elements: hydrogen. and oxygen. It is a colorless and odorless transparent liquid at normal temperature and pressure.
The thermal stability of water is very strong. When water vapor is heated above 2000 K, only a very small amount of water dissociates into hydrogen and oxygen. However, water dissociates into hydrogen under the effect of electricity (electrolysis) and oxygen.
The density of water is maximum at 3.98 ℃, or 1 × 10?kg/m?. When the temperature is above 3.98℃, the density of water decreases as the temperature increases. At 0~3.98℃, the density increases with increasing temperature.
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Importance and impact
1 On the climate
Water has a regulating effect on climate. Water vapor in the atmosphere can absorb 60% of the ground's radiation and then return to the ground as reverse atmospheric radiation, thereby insulating the ground.
Water has a high specific heat capacity. Oceans and land water bodies can absorb and store heat in summer to keep the temperature from being too high; in winter, they can slowly release heat to keep the temperature from being too high; too low. Due to different conditions, water may also appear as hail, fog, dew, frost, etc. and affect the climate and human activities.
2. Landforms
71% of the Earth's surface is covered in water. Seen from the air, Earth is a blue planet. Water erodes rocky soils, silts up river channels, carries silt, creates plains and modifies morphologyof the earth's surface.
3. For living things
Water is an important component of all living organisms. Water makes up 70% of the human body and 98% of jellyfish are water. Water facilitates certain biochemical reactions, such as digestion in animals and photosynthesis in plants. Because water can reduce temperature through evaporation, water plays an important role in maintaining the temperature stability of living organisms, such as animal sweat and plant transpiration.
4. For human society
Water is an important resource for human life. It is necessary to consume 2 to 3 liters of water per day and it provides water for people's daily lives. and industrial and agricultural production, particularly agriculture which requires large quantities of water for irrigation.
With the development of science and technology, people have built projects ofwater conservation to combat natural disasters such as waterlogging and flooding. As a result, some research areas specifically related to water have been established, such as hydraulics, hydrology, water treatment, etc., and even the industrial aquaculture industry which depends on water for its survival came into being.
Baidu Encyclopedia - Water