To obtain common salt from seawater, a process of evaporation and crystallization is used. Here’s a detailed explanation of the process:

1. Collection of Seawater
- Seawater, which contains about 3.5% salt, is collected from oceans or seas.
- This water contains various minerals along with sodium chloride (common salt).

2. Evaporation Process
- The collected seawater is placed in shallow ponds or basins.
- Sunlight is the primary source of heat, which helps in the evaporation of water.
- As the water evaporates, the concentration of salt increases.

3. Crystallization of Salt
- Once the water has evaporated significantly, salt begins to crystallize.
- These salt crystals form on the bottom of the evaporation ponds.
- The remaining water is drained off, leaving behind the salt.

4. Harvesting the Salt
- The crystallized salt is then carefully harvested by hand or with machinery.
- It may contain impurities, so it is washed to remove any remaining minerals and debris.

5. Drying and Packaging
- The washed salt is dried in the sun or using mechanical dryers.
- Once dried, it is packaged for sale and distribution.

6. Uses of Common Salt
- Common salt obtained from seawater is used in cooking, food preservation, and various industrial applications.
- It is also essential for human health and is used in many chemical processes.
This process highlights how seawater, a resource abundant in nature, can be transformed into common salt through simple yet effective methods.