1. Not finding help here? Sign up for a free 30min 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!

Please check my work energy required to raise temp by 10degthanks

  1. Feb 20, 2011 #1
    1. The problem statement, all variables and given/known data

    You want to heat 1 L of water by 10 ºC, and so you heat it with a mechanical egg beater that is powered by a 1 kg mass on a rope over a pulley. How far does the mass have to descend to supply enough work for heating the water?

    2. Relevant equations
    |work| = mg(x_f - x_0)
    C_P (liquid water) = 75.3JK^-1mol^1


    3. The attempt at a solution
    I first asked myself how much energy does it take to increase the temp of 1kg of water by 10degC.
    Heat capacity of water (above) is the energy required to heat 1 mol of water by 1deg.
    So I first determined how many moles of water i have:

    1L = 1kg = 1000g * (1mol/18.01g) = 55.5mol of liquid water

    Therefore 55.5mol *75.3JK^-1mol^1 = 4179.15J/K * 10K = 417915.0J

    So it requires 417915.0J to raise the temp of 1kg water by 10degC.

    This is the work required also because work is also in joules, --energy.

    Then i used the formula for mechanical work to determine the value for delta x.

    |work| = mg(x_f - x_0)

    417915.0J(1kJ/10000J) = 1kg(9.81m/s/s)(x_f) (i got ride of x_0 because I set scale so that x_0 = 0)

    x_f = 42.6m

    So the mass has to descend through 42.6m in order to heat 1kg of liquid water by 10 degC.

    Is this correct or if not please help..thanks alot. I also have some other questions about the problem but i dont want to ask until i know if my answer is correct...thank you again
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted
Similar Discussions: Please check my work energy required to raise temp by 10degthanks
  1. Check my work (Replies: 1)

Loading...