YouTube: https://youtube.com/watch?v=iF6MS9_sdzg
Previous: Aphids: Weird Poop, Weirder Babies
Next: SciShow Talk Show: Crash Course Physics Host Dr. Shini Somara & Sydney the Brush-Tailed Bettong

Categories

Statistics

View count:1,383,388
Likes:26,896
Dislikes:575
Comments:2,283
Duration:02:26
Uploaded:2016-04-12
Last sync:2018-05-02 16:50
You’re going to bed, and you take a sip of cool delicious water, and it’s so refreshing. But, when you wake up and take a swig, that water now tastes like bleh. What’s going on here? Watch this SciShow Quick Question to find out!

Hosted by: Michael Aranda
----------
Support SciShow by becoming a patron on Patreon: https://www.patreon.com/scishow
----------
Dooblydoo thanks go to the following Patreon supporters -- we couldn't make SciShow without them! Shout out to Justin Ove, Coda Buchanan, Lucy McGlasson, Accalia Elementia, Mark Terrio-Cameron, Saul, Kathy & Tim Philip, Kevin Bealer, Christopher Collins, Thomas J., charles george, Andreas Heydeck, Patrick D. Ashmore, Justin Lentz, Will and Sonja Marple, Ed Shelley, Chris Peters, Tim Curwick, Philippe von Bergen, Fatima Iqbal.
----------
Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records: http://dftba.com/scishow
----------
Looking for SciShow elsewhere on the internet?
Facebook: http://www.facebook.com/scishow
Twitter: http://www.twitter.com/scishow
Tumblr: http://scishow.tumblr.com
Instagram: http://instagram.com/thescishow
----------
Sources:
http://www.chemistry.wustl.edu/~edudev/LabTutorials/Water/PublicWaterSupply/PublicWaterSupply.html
http://www.wired.com/2015/08/big-question-tap-water-go-stale-overnight/
http://www.smithsonianmag.com/smart-news/whats-stale-glass-water-180955926/#3qFa1RQ4heTzzcXQ.99
http://www.epa.gov/your-drinking-water/table-regulated-drinking-water-contaminants#one
http://time.com/3104999/old-water-sick/
(Intro)

Michael: Have you ever poured yourself a nice, cool drink of water before bed and woken up to a glass of blehhhh? In just a couple of hours, your refreshing water turned tepid and kind of musty. But why?

Well, we have a couple guesses about why water goes stale, and it's all about the chemistry. Your drinking water isn't just a pure collection of H2O molecules. It has a lot of other ions and molecules in it too, which can change over time and affect how the water tastes.

So let's first start with carbon dioxide. It's the stuff you exhale, the stuff in soda that makes it fizzy, and that pesky gas that's making the oceans more acidic. And your cup of water is to some extent like a tiny ocean. Water is an excellent solvent, which means it's really good at dissolving lots of other substances, including gases, until it reaches equilibrium with the atmosphere. So as water sits in your room, it gradually absorbs some carbon dioxide from the air. The water molecules and carbon dioxide molecules can then react to each other to form carbonic acid, which lowers the pH of the water, making it slightly acidic. And a little less tasty.

So gas entering the water can affect its flavor. But gas leaving the water can too. Before tap water makes its way to your faucet, water treatment centers sometimes add compounds containing chlorine, up to 4 milligrams per liter, in order to purify it. Chlorine is really good at killing  any bacteria or viruses that might be floating around, which is why we also chlorinate swimming pools. But if you've ever accidentally swallowed any pool water, you know it's kinda gross. So then why does a cool glass of tap water taste good? Well, if you're used to drinking slightly chlorinated water, you might associate a tiny bit of chlorination with a cleaner, crisper taste, and when you let a glass of water sit out, the chlorine will dissipate back into the air as a gas, which could change the taste of your water and make it seem less refreshing.

These chemical factors aside, the main reason for the stale taste could be the most obvious: temperature. Basically, cold temperatures suppress taste. Warmer water has faster-moving molecules, which in turn amplify the flavors you can detect with your taste buds. So when you drink a cold glass of water, you might not be tasting all of the subtle flavors it already has inside, kind of like the subtle flavors in a glass of wine.

The good news? Leaving your glass of water out overnight won't hurt you. Even if it tastes a little gross. So: drink up.

Thanks to Patreon Patron Carston from Switzerland for asking this question. Thanks to all of our Patrons, who keep these answers coming. If you'd like to submit a question to be answered, just go to patreon.com/scishow, and don't forget to go to youtube.com/scishow and subscribe.

(Outro)
 
He noticed that the ice cream mixture made with hot milk froze faster than the mixture made with cold milk.