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Rain – Definition, Causes, Importance, Acid Rain

Last Updated : 20 May, 2022
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Rain is made up of water droplets that have condensed due to evaporation. Cloud formation occurs during the water cycle. Precipitation is another word for rain. Water is absorbed from various bodies of water, with a major portion of it vaporizing and entering the atmosphere. Water evaporates as a result of a variety of biological activities. As the hot air with water molecules rises above ground level, it expands and cools after reaching a proper height. When water vapor cools, it condenses into droplets of water. This process is known as condensation.

It is aided by elements suspended in the air, such as dust and other particles, which speed up the process and form the nucleus for these droplets. A cluster of such droplets joins together to generate massive water masses that we see as clouds. When they become large and heavy, they fall to the ground as rain. As a result, they are precipitations. If the temperature is low, these precipitations may take the form of snow, hail, or sleet.

Rain Formation


Cloud Formation

Clouds occur as a result of water molecules evaporating from the earth’s surface due to their lower weight. When these water vapors reach higher altitudes, they cool down and stop escalating once they hit saturation, also known as the frost point. Droplets now float in the air, forming clusters with other droplets before combining to form massive water masses that we see as clouds.

Classification of Precipitation

  • Raindrop: Coalescence occurs when water droplets merge to produce larger water droplets, and when water droplets freeze onto a crystal of ice. The rate of descent is thought to be negligible, which explains why clouds do not fall from the sky. Precipitation is only feasible when those droplets coalesce into larger drops due to turbulence, in which water droplets clash, forming even larger droplets. Droplets eventually descend and grow heavy with coalescence and resistance, eventually falling as rain.
  • Snowflakes: When the temperature freezes the tiny cloud droplets, the crystals can expand in size at the expense of the droplets when they evaporate due to water vapor. Because of their bulk, these drops descend from the atmosphere as snowflakes.
  • Hail: When super cooled droplets collide with dust and grit in storm clouds, hail occurs. The storm’s updraft lifts the hailstones, which are then lifted again as the updraft subsides.

Precipitation is defined in meteorology as any outcome of atmospheric water vapor condensation that falls under the influence of cloud gravity. Drizzle, rain, sleet, snow, ice pellets etc. are the most common types of precipitation. Precipitation occurs when water vapor saturates a section of the atmosphere, causing the water to condensate and fall. Because water vapor does not condense sufficiently to precipitate, fog and mist are colloids rather than precipitation. Cooling the air or adding water vapor to the air are two methods that may lead to air saturation.

Importance of Rain

  1. Rain showers aid in the growth of plants. No plant will be able to develop without rainwater.
  2. Rain is a crucial component of the water cycle that contributes to the deposit of the majority of freshwater on Earth. It supports a variety of ecosystems and aids in survival.
  3. It supplies water to hydroelectric facilities, which use it to generate energy.
  4. It is particularly beneficial to crop growth since it is a method of crop irrigation on huge fields.
  5. It aids in the maintenance of groundwater levels.
  6. Humans collect rainwater to conserve it for later use in bathing, cooking, cleaning, and drinking. It is known as rain harvesting. This approach aids in the reduction of water bills by providing an alternate supply of water during water restrictions while also maintaining a healthy and clean garden.
  7. Rain serves to cool the atmosphere and reduces the Earth’s extreme temperatures. As a result, it is a huge relief when it rains throughout the summer.

Acid Rain

Acid rain is composed of highly acidic water droplets that form as a result of air pollutants, notably the disproportionate levels of sulfur and nitrogen produced by cars and manufacturing operations. It is commonly referred to as acid rain, since it encompasses a wide range of acidic precipitation. Acidic deposition occurs in two forms: wet and dry. 

Conceptual Questions

Question 1: What causes precipitation reactions?


When a solution containing a certain cation is mixed with another solution containing a specific anion, an insoluble compound is frequently formed. A precipitate is defined as a solid that divides.

Question 2: Is precipitation an indication of a chemical reaction?


Precipitation can also be a sign of a chemical reaction. A chemical reaction happens when a silver nitrate solution is put into a sodium chloride solution, generating a white silver chloride precipitate.

Question 3: What is an example of precipitate formation?


A chemical reaction happens when a silver nitrate solution is put into a sodium chloride solution, generating a white silver chloride precipitate. A yellow lead(II) iodide precipitate is formed when the potassium iodide solution reacts with the lead(II) nitrate solution.

Question 4: Is Salt a precipitate?


The precipitate is the insoluble salt that precipitates out of the solution, thus the reaction’s name. Precipitation reactions in solution can aid in determining the identity of various ions.

Question 5: What influences precipitation?


The three important elements that determine precipitation are prevailing waves, the existence of mountains, and seasonal waves. Mountain ranges are groups of mountains linked together by high soil. A mountain range in the direction of the prevailing winds can also impact where precipitation occurs.

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