The purest form of water is distilled water. Distilled water is water that has been boiled and then condensed back into a liquid. This process removes all impurities, including minerals, salts, and other chemicals. Tap water, rainwater, and groundwater all contain impurities, so they are not as pure as distilled water.
Tap water is water that comes from a municipal water supply. It is treated to remove harmful bacteria and other contaminants, but it still contains some minerals and other impurities. Rainwater is water that falls from the sky. It is naturally filtered by the atmosphere, but it can still contain pollutants from the air, such as dust and pollen. Groundwater is water that is found underground. It is filtered by the soil and rocks, but it can still contain minerals and other impurities.
Distilled water is the purest form of water because it has been through a process of distillation. Distillation is a process of heating a liquid until it turns into a gas, and then cooling the gas back into a liquid. This process removes all impurities from the liquid, leaving behind only pure water.
Distilled water is often used in laboratories and other settings where pure water is required. It is also used in some medical procedures and in some types of water filters.