1. PF Insights is off to a great start! Fresh and interesting articles on all things science and math. Here: PF Insights

Pressure and Temperature - Quick Concept Check

  1. Pressure and Temperature -- Quick Concept Check

    1. The problem statement, all variables and given/known data

    A fixed amount of ideal gas is held in a rigid container that expands negligibly when heated. At 20°C the gas pressure is p. If we add enough heat to increase the temperature from 20°C to 40°C, the pressure will be less than 2p.

    2. Relevant equations

    pV=nRT

    p_1/T_1=p_2/T_2

    3. The attempt at a solution

    Initially I thought the solution was simple. Solving for p_2, we have (p_1*T_2)/T_1. Plugging in 40 for T_2, and 20 for T_1 gives us 2p. Because volume, number of moles, and R are all constant, I thought it just came down to the relation between pressure and temperature, but it turns out the pressure is less than 2p, which I do not understand. Just looking for some clarification....

    Thank you!
     
  2. jcsd
  3. jedishrfu

    Staff: Mentor

    Re: Pressure and Temperature -- Quick Concept Check

    shouldnt T be in Kelvins ie absolute temperature?
     
  4. Re: Pressure and Temperature -- Quick Concept Check

    You're right, but I guess I was thinking since 1 celsius degree is equivalent to 1 kelvin, that it shouldn't matter. Essentially, I was thinking if volume is constant, then doubling the temperature should double the pressure, no?

    Or does is it significant that we use kelvins, in which case it does turn out to be less than 2p?
     
  5. Re: Pressure and Temperature -- Quick Concept Check

    Mathematically, think of Celsius as (kelvin -273)
    if you double Celsius, you get (2k - 546) so essentially you double both the difference between Kelvin and Celsius as well as the change in kelvin. You ALWAYS should use Kelvin, It helps.
     
  6. Re: Pressure and Temperature -- Quick Concept Check

    Ok, should have caught that. Thanks guys.
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?
Similar discussions for: Pressure and Temperature - Quick Concept Check
Loading...