Process of Evaporation

Our Objective

To understand the process of evaporation.

 

Theory 

Evaporation is the process by which water changes from a liquid to a gaseous state. While the boiling temperature of water is 100 degrees Celsius, it evaporates very slowly at 0 degrees Celsius. When the temperature rises, the rate of evaporation increases with it. However, the rate at which water evaporates varies depending on the temperature and the amount of water that needs to be evaporated. Hence, the phenomenon of change of a liquid into vapours (gases) at any temperature below its boiling point is called evaporation. The preparation of common salt, drying wet clothes, hair in the sun, and ironing of cloth are examples of evaporation. Evaporation is a basic purification method used in our day-to-day life. Condensation is the process by which the vapour or gaseous state of water is converted to a liquid state; it is the opposite of evaporation. 

 Process of Evaporation 

When a liquid is heated, it evaporates. This implies that the molecules in the liquid should acquire kinetic energy. When the kinetic energy is gained, the molecules of a liquid vibrate more rapidly. As a result, the liquid changes its state of matter from liquid to gas. 

At all temperatures, including room temperature, all liquids undergo evaporation. Nevertheless, the evaporation of liquids with higher boiling points occurs at a significantly slower pace and may not be readily observable. Conversely, liquids with lower boiling points experience rapid evaporation. 

Another thing to keep in mind is that evaporation is a slow process that can be increased or slow down by external factors. The various factors that affect the rate of evaporation are temperature, surface area, wind speed and humidity.

                                                                                        

Factors affecting evaporation 

Temperature: 

  • As the temperature rises, the rate of evaporation rises as well. 
  • At higher temperatures, the molecules are moving faster; therefore, it is more likely for a molecule to have enough energy to break away from the liquid to become a gas. 

Surface area:

  • As the surface area increases, the rate of evaporation also increases. 
  • As more surface area is exposed to air, water molecules can absorb more heat energy from their surroundings. 

  Wind speed:

  • The rate of evaporation is directly proportional to wind speed. As the wind speed increases, the rate of evaporation also increases. 
  • Higher wind speed leads to increased airflow over the liquid’s surface, reducing the formation of a humid air layer.

  Humidity:

  • The rate of evaporation is inversely proportional to humidity. As the humidity decreases, the rate of evaporation increases and vice versa.
  • Higher humidity means less evaporation because the air already holds a lot of moisture content, so there is less room for more water to evaporate into the air. On the other hand, lower humidity leads to faster evaporation because air can take in more water vapour. 

 

Learning Outcomes 

  • Students understand the term “Evaporation”. 
  • Students understand the process of evaporation as the state of matter changes from liquid to gaseous state. 
  • Students are now better prepared to perform the experiment in the real lab after experiencing it in the virtual lab.