You think you’re doing something nice for yourself by leaving a cool glass of water on your nightstand. But come morning, you take a sip and — “Wait, I poured this last night?” Why does your water taste so funky after sitting on your bedside table for mere hours? There’s a pretty scientific reason for the staleness, so get your thinking caps on, kids.
According to an April 2016 episode of SciShow, your nightstand water’s strange new flavor has to do with the compounds within the water itself. Water isn’t just comprised of H2O. It has a bunch of other molecules and ions floating around in it, too, and those ions and molecules can change throughout the night as they affect the water’s taste.
Water is also a solvent, which means it can dissolve other substances including gasses like carbon dioxide (the stuff we exhale). When carbon dioxide, or CO2, reacts with H2O, carbonic acid forms and slightly acidifies the water. No one likes acid-y water — even if it’s just ~slightly~ acidic.
But just as gas entering the water can affect the taste, so can gasses leaving it. Tap water oftentimes contains chlorine, a substance used by water treatment facilities to purify and cleanse the water.
If you’re used to drinking water from the tap, then you’ve probably grown accustomed to the slight taste of chlorine. But as we let that glass of water sit out on our nightstand, the chlorine gas leaves the water and is absorbed into the air. Not tasting that normal level of chlorine could make us think that the water tastes mustier than usual.
But as SciShow explains, temperature is probably the biggest culprit of gross-ifying our water. Colder temperatures suppress our ability to taste. So when we drink cold water, we’re probably glossing over a lot of its naturally occurring flavors — flavors that we pick up when the water warms.
[fm_youtube url="https://www.youtube.com/watch?v=iF6MS9_sdzg"]Even though it might taste a bit less than gourmet, your nightstand water is perfectly fine to drink. Oh, the struggles we go through to stay hydrated!
