Boiled water often tastes different from raw water due to several factors:

1. Dissolved Gases: Boiling water expels dissolved gases, like oxygen and carbon dioxide. These gases can affect the taste and smell of water. When they are removed, the taste might seem flat or less fresh.
2. Mineral Concentration: As water boils, some of its volume is lost to evaporation, which can concentrate the minerals and impurities left behind. This change can alter the taste.
3. Chemical Reactions: Boiling can cause chemical reactions in the water or in any impurities present, which might change its flavor. For instance, certain minerals might interact with each other under high heat, affecting taste.
4. Container Effects: The taste of boiled water can also be influenced by the container used for boiling. For instance, a metal kettle might impart a slight metallic taste if it’s not well-maintained.
5. Temperature Sensitivity: Cold or room temperature water often tastes fresher and more crisp, while boiled water, once it cools down, can taste different because it’s no longer chilled and its volatile components have changed.

So, the difference in taste mainly comes from the changes in dissolved gases, mineral concentration, and potential chemical reactions that occur during boiling.