Final answer:
Blowing into water does not significantly change the pH. The pH of water depends on dissolved ions, and adding chlorine can lower the pH. Dissolved carbon dioxide can also make water slightly acidic.
Step-by-step explanation:
Blowing into water does not significantly change the pH of the water. The pH of water depends on what ions are dissolved in the water. Adding chlorine to water often lowers the pH. The pH of water can become slightly acidic due to dissolved carbon dioxide gas, which forms carbonic acid.