Why does my bottled water have an expiration date? Does this stuff actually go bad?
Hi everyone, Julian here for DNews. Have you ever left a glass of water out overnight.
And the next day, taking a drink, and noticed it tasted funny?
Does that mean the water is going bad, or what's happening here?
Well the water itself doesn't have any sugars or proteins like food, so microbes aren't consuming it and rotting it.
However, that's not to say the chemistry of the water hasn't changed.
By being exposed to air, the water absorbs some CO2, and a tiny portion of that, about 0.13%, is converted into carbonic acid.
Some carbonic acid will then lose a proton or two, forming bicarbonate or carbonate respectively.
This lowers the pH of water, making it slightly acidic and changing the taste.
So does that mean it's unsafe? Probably not, no. Unless you are a shellfish.
