1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Inflating objects by evaporating urine

  1. Nov 24, 2011 #1
    Hi there,

    Im conducting an experiment in which i am boiling a pot of urine that is covered with a plastic sheet.

    As the water evaporates from the urine the steam causes the plastic sheet to inflate creating a domed shape.

    The steam then condenses on the domed plastic sheet and drips down to the edges of the pot, collecting in a separate recepticle.

    I am wondering for a given amount of water/urine, say 100ml, how much does the amount of air within the pot increase as it evaporates.

    Thanks for any help.

  2. jcsd
  3. Nov 24, 2011 #2
    What do you mean by "air"?
  4. Nov 25, 2011 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    During the boiling process you constantly have evaporation and condensation, so there is no simple answer. The faster you boil it the more steam will exist at one time inside the container.
  5. Nov 25, 2011 #4
    Hi, thanks for the reply, ive attached a picture which hopefully makes the experiment i was talking about a bit clearer.

    The urine only fills a few millimeters of the pot. A container is then placed in the centre of the pot and the pot is covered with cling film. The pot is heated, water evaporates and condenses on the cling film and drips down into the central container.

    The more the pot is heated, the more the cling film inflates due to the increased temperature of the air trapped inside of the pot at the start, and the steam that results from the heating. I was wondering if this rate of expansion is measurable.

    Attached Files:

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook