NCERT 5th Class (CBSE) Science: Air and Water

Question: Describe the different ways by which insoluble impurities can be removed from water.

Answer: the different ways by which insoluble impurities can be removed from water are the following:

1. Filtration
2. Sedimentation and Decantation
3. Loading

Floating:

In this process insoluble impurities are removed from water by passing the impure water through a filter paper. A circular piece of filter paper is taken and folded twice to make a cone and this is kept inside a funnel. A flask is kept below the funnel and the mixture is houred into the flask through the funnel. Sand is retained on the filter paper and clean water is obtained in the flask.

Sedimentation and Decantation:

1. The mixture of insoluble impurities for example, (mud ) and water is allowed to stand undisturbed in a beakker.
2. After some time the mud settles down at the bottom of the container as sediments. This process is called sedimentation.
3. Clean water can then be poured out into a seperate container without disturbing the sediments. This process is called decantation.

Question: Describe the different ways by which soluble impurities can be removed from water.

Answer: The different ways by which soluble impurities can be removed from water are:

1. Evaporation: In this process a solution containing soluble impurities like common salt or sugar is heated. After some time water will change into steam and the soluble impurity will be left behind in the container.
2. Distillation: This process involves the following steps:
   (i) Impure water is taken in a round bottomed flask and heated.
   (ii) On heating, water changes into steam and the impurities are left behind. Whwn the steam through the condenser, it cools and turns into water (liquid).
   (iii)Pure water is collected in a flask.