How is rainwater classified in terms of mineral content?

Rainwater is classified as soft water due to its low mineral content. The process of rain formation involves the evaporation of water, which leaves behind minerals and impurities. As rain falls, it can dissolve certain gases from the atmosphere, like carbon dioxide, resulting in slightly acidic water, but it does not typically carry a high concentration of minerals or salts that would classify it as hard water.

Soft water is characterized by low concentrations of calcium and magnesium, which are the two primary minerals found in hard water. Since rainwater is essentially distilled from its original source, it has very little of these minerals, making it soft. This property makes rainwater particularly useful for various applications such as irrigation and washing, where the presence of hard minerals could lead to scaling or soap scum.

In contrast, tap water is treated and may contain various minerals, while groundwater is often mineral-rich, typically classified as hard due to the dissolution of minerals as it moves through soil and rock.