We all know that 70% of the earth’s surface is covered with water, and rainwater is the only freshwater source. Water evaporates from the sea, ponds, and lakes due to the heat of the sun. It rises above and forms clouds and cloud moves with the wind, and we get rain from clouds. Rainwater gets collected in rivers and flows to the seas and ocean. It is a continuous process that goes on every second, and it is called the Water Cycle.
Apart from seas and ocean water is contained in the soil, atmosphere and all living things. More than half of our body consists of water.
Rainwater seeps through the ground and gets collected below the rocks present under the soil’s surface. It seeps in deeper till it reaches the solid surface, and it remains there. This water is called underground water. However, the overuse of groundwater is causing scarcity.
Impurities in water
The water that we get has certain impurities, though they may not be visible to the naked eyes. There are many ailments of using impure water for more extended periods like dysentery, Cholera, water pollution, Typhoid, and jaundice. Therefore, it is essential to make sure that the water we use is clean and free from impurities.
Soluble impurities are that dissolved in water like microorganism, Biomolecules, Dissolved Gases, Dissolved Organic Compounds, Suspended particles, and Dissolved Inorganic Compounds. They are all microscopic and not visible to the naked eye. The salt present in seawater is an example of soluble impurity. Some impurities such as Mud particles, leaves are not soluble in water. They are called insoluble impurities. Impure water is unfit of consumption. It is, therefore, essential to purify water to remove soluble as well as insoluble impurities.
We can use different methods to remove impurities.
Water present in nature often contains insoluble impurities like Soil particle, twigs, and Animal Excreta, making it unclean and unfit for use. Sedimentation is the method of removing such impurities straightforwardly. If the mixture of soil and water is stirred and left undisturbed for a few hours, the soil particles start settling down slowly at the vessel’s bottom. It is only when the water is clear that the process of sedimentation is complete. The solid impurities that settle down at the bottom of the vessel are called the sediments.
The water collected over the impurities formed during sedimentation can be separated by draining it into another beaker by decantation. The process of draining off the transparent liquid particles after sedimentation is called decantation. During decantation, it is essential to leave behind a small amount of liquid in the container to prevent the sediment from flowing out of the container and getting mixed with the clear liquid.
The perfect example of this method of removing insoluble impurities is when we strain the tea into a cup using a tea strainer. Filteration is the physical process of separating insoluble substances from liquids using a fine cloth, filter paper, and a steel strainer. The liquid containing insoluble impurities are poured into a funnel lined on the inside with a filter paper or fine cloth. The clean water passes through the filter, leaving all the insoluble impurities behind, as is collected in a jar kept below the funnel. The filtered water does not contain any insoluble impurities and is called a filtrate. The insoluble impurities left on the filter paper is called the residue. Boiling the Filterate kills the microscopic impurities in it, such as germs and microbes.
Water turns into vapor when it is heated. This process is called evaporation.
Distillation is a method of purifying a liquid. In this process, the liquid is vaporized, condensed, and collected separately. When is saltwater is heated in a Flask, the water slowing starts evaporating into water vapor due to heat. The water vapors, when cooled, give pure water with salt left behind in the flask. The substance that’s left in the flask is salt.
When water is boiled for about 20 minutes, the germs present in it are killed. The boiled water then must be stored in clean vessels and bottles.
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