Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The taste of hot water vs. cold water

  1. Feb 23, 2012 #1
    In my chemistry class today we learned about equilibrium and how temperature affects the equilibrium constant. An example that was cited was this chemical equation:

    H2O <--> H3O+ + OH-

    I learned that increasing the heat of the water will drive the equilibrium toward the right side, increasing the concentration of hydronium and hydroxide ions.

    I raised my hand in class and asked "is that why hot water tastes bad? you know, because of all the hydronium, perhaps it reacts with the ions in our mouths or something and creates a bad taste in our mouth? maybe?"

    I figure it cant be JUST because it's hot. Even water that you've left in your hot car all day tastes like ****, even if you can tolerate the temperature. It's just awful tasting. I know that the ratio of hydronium to hydroxide would remain constant and wouldn't necessarily change the pH of the solution, but its more complicated because of equilibrium yada yada yada, right?

    My teacher did not have an answer.

    So.... yes? no? maybe?
  2. jcsd
  3. Feb 24, 2012 #2
    hello coitus,
    This may be not the good answer but i will try to explain your question with what i think a logical answer. Water we drinks is not 100% pure H20; It contains dissolved gases and organic matters. When we are heating the water the dissolved gases escapes and organic matters denatures.This may be the reason why taste of water changes when heating
  4. Feb 24, 2012 #3


    User Avatar

    Staff: Mentor

    To add to what newbe wrote, pH of the water we drink is never exactly 7, because of the dissolved salts (mostly carbonates) present.
  5. Feb 24, 2012 #4
    Agreed on the dissolved gasses...

    FWIW, 'utility-supplied' water may have dissolved chlorine, too. I find our tap water is barely drinkable unless I slosh in 5~~10% of 'sparkling water' to flush the chlorine, replenish the CO2 and lower the pH a bit...

    Uh, there was a superb short story by, IIRC, A C Clarke, about Lunar base astronauts who found their water supply gradually tasted too 'wrong' to drink. They could only stomach the recycler's limited output, eventually expired of heat exhaustion and thirst. Flavour turned out to be a surfeit of dissolved oxygen which they could have removed in minutes using an improvised 'boiling stone' and the vacuum outside the base...
    Last edited: Feb 24, 2012
  6. Feb 25, 2012 #5
    Now, THAT's what I call a magnificent story... Thanks for sharing :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook