Hypothesis: The temperature of the cup of water drops to 20°C.
The mass of water is 0.2 kilograms
According to the caloric formula Q=Cm·△T
Q =4.2×10^3×0.2×(100-20)
=6.72×10^4 (J)
In other words, a cup of water at 100°C has about 67,200 joules of heat
100°C the vapor of wateris warmer. Because when water vapor at 100°C meets the skin, it first liquefies into water at 100°C, and then continues to cool and release heat, since a large amount of heat is released during the previous liquefaction process, it is better than 100°C. Water CThe burnmust be severe.
A gasification process that occurs only on the surface of a liquid. Evaporation can occur at any temperature. The evaporation process absorbs heat and evaporates to produce cooling.
Factors that affect speedevaporation: temperature, humidity, surface of the liquid, air flow over the surface of the liquid, etc.
The process by which water changes from a liquid or solid to a gas and escapes into the atmosphere is called evaporation. This means that water turns into water vapor when it comes into contact with air at normal temperature. Evaporation refers to the amount of water evaporated and dispersed into the air over a certain period of time.
Generally expressed in millimeters of thickness of the evaporated water layer. The amount of water evaporated from the water surface or soil is measured using different evaporators. Generally, the higher the temperature, the lower the humidity, the greater the wind speed, and the lower the air pressure, the greater the evaporation; conversely, the greater the evaporation. weak ;
Measuring soil evaporation and water surface evaporation is veryimportant in agricultural production and hydrological works. Areas with little precipitation, groundwater sources, and little runoff are prone to drought if evaporation is significant.
And it can evaporate at any temperature. From a microscopic point of view, evaporation is the process by which liquid molecules leave the liquid surface. Since the molecules in the liquid are constantly moving irregularly, their average kinetic energy corresponds to the temperature of the liquid itself.
Due to the irregular motion and collisions of molecules, some molecules always have greater kinetic energy than the average kinetic energy at any time. These molecules have sufficient kinetic energy.
If they are close to 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 detach from the surface of the liquid and fly away, becoming this kind of vapor liquid, this is the phenomenon of evaporation.
Molecules that fly away can 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.
During the evaporation process, molecules with higher than average kinetic energy fly away from the surface of the liquid, while the average kinetic energy of molecules remaining inside the liquid decreases. Therefore, during the evaporation process, if the outside world does not replenish the energy of the liquid, the temperature of the liquid will drop.