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

Homework Help: Boiling water - oscillation; when oxygen needs more room

  1. Jul 5, 2006 #1
    I understand that when the oxygen molecules are heated up in a pot of water, they will vibrate increasingly as they get hotter. I guess that's what those little bubbles are at the bottom of the pot.

    At some point, they will suddenly release. Is there a name for this threshold and a way to measure it? And am I correct in thinking that they are pushed up once they reach that certain point (that threshold)?

    Finally, does this mean that the water is now saturated with (or has excess of) hydrogen?
  2. jcsd
  3. Jul 5, 2006 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    The bubbles are water vapour, not oxygen.

    It is called boiling. It occurs when the vapour pressure of a liquid is equal to the ambient pressure.

    The water is not chemically altered by boiling. The bubbles release saturated water vapour. That is why a boiling kettle steams.

  4. Jul 5, 2006 #3
    If only releasing the hydrogen from water was that easy, we'd have hydrogen cars on the roads already. ;)
  5. Jul 5, 2006 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    An interesting point to note however, is that when water is heated it becomes more acidic. This is due to the auto-dissociation of water (which can be attributed to the fact the water is amphoretic). Slightly off point but what the hey.:smile:
  6. Jul 5, 2006 #5
    Okay, thanks. Much appreciated.

    But I don't understand how the vapor can linger on the bottom and suddenly release or pop up. I guess that point is the threshold I am trying to figure out. Any input, or better yet, a direction to point me to study further? I don't even know if this is chemistry or physics.

    I also am curious why these bubbles are isolated. Why isn't this occurrence more evenly distributed? I mean, there is area on that surface where there aren't any bubbles. As I look into the pot, there are points where the bubbles form rapidly, creating a line of released bubbles.
  7. Jul 5, 2006 #6


    User Avatar
    Gold Member

    The bubble of vapour is held in place by surface tension of water. Once the bubble gets large enough, its bouyancy will overcome this adhesion.

    The bubbles cannot form just anywhere, they have to form at http://en.wikipedia.org/wiki/Nucleation" [Broken].
    Last edited by a moderator: May 2, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook