Here's why:

* pH Scale: The pH scale measures acidity and alkalinity. A pH of 7 is neutral. Values below 7 are acidic, and values above 7 are alkaline (also called basic).

* Soda Water's pH: Soda water has a slightly acidic pH, typically around 3-4. This is due to the dissolved carbon dioxide (CO2), which forms carbonic acid in water.

* Alkaline Water: Alkaline water, on the other hand, has a pH of 8 or higher. It's usually produced by adding minerals like calcium, magnesium, or potassium to water.

Therefore, while soda water is carbonated, it's not alkaline. It's actually slightly acidic.