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1. Show how evaporation and condensation takes places
Ans. Evaporation is the process where some of a liquid becomes a gas at temperatures below the boiling point. In other words, its molecules escape the body of the liquid and move freely away, as a gas. An example is when water in a pan evaporates until there is no liquid left in the pan. The reason this happens is because some molecules have high enough energy to escape the surface tension of the liquid. Evaporation results in the liquid becoming cooler. Blowing on the liquid increases the evaporation.
Condensation is the opposite of evaporation. It takes place when water vapor in the air condenses from a gas, back into a liquid form, and leaves the atmosphere, returning to the surface of the Earth.
2. Show that how air contains water vapor.
Ans. Water vapor is the gas phase of water. Water vapor is produced from the vaporization
(evaporation or boiling) or from the sublimation of ice. Under normal atmospheric
Conditions, water vapor is continuously evaporating and condensing.
The amount of water vapor in the air is very low in extremely arid areas and at places where the temperatures are very low. Temperature determines the maximum amount of water vapor that can exist in the air.
Experiment: Place the clear glass container or smooth shiny can on a firm flat surface. Fill the container about three-fourths full of water. Place one of the thermometers in the container of water and place the other thermometer on the surface beside the container. Immediately observe and record the temperatures of both thermometers. Add ice to the container of water and use a stirring rod to stir the ice and water. Carefully observe the outside surface of the container and look for any changes in the appearance of the surface. As soon as you observe changes on the surface of the container, carefully record the temperature of the water and the temperature of the surface...
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