Here is a link to the data sheet. Actual numbers and a discussion of correct precision and significant figures foR this lab, with general APPlIcationS, will be posted soon.

Objective---To measure pressure as a function of temperature and to extrapolate to absolute zero. 

reference---Ch. 13. See section 13-6.  See the Gay-Lussac’s Law, page 363, which assumes volume V is constant. See figure 13-13 (a), but assume the vertical axis is pressure P instead and that the volume is constant. In other words, assume the straight line is a graph of P vs T. Check out the T intercept !
Computations---You should be able to find the slope and the x or y intercept of a line from  two data points. You should also be able to make a simple chart in Excel.

Equipment:
Bucket                                                                                   Table clamp

Pressure gauge                                                                   Long and short rod

2 Thermometers                                                                 Rod clamps

Electric range

 

Procedure:

  1. Fill the bucket with water so the bulb of the pressure gauge can be completely
    submerged .Place the bucket on the electric range and submerge the bulb under the water; secure the pressure gauge with rods and clamps as in the demonstration set-up.   
  2. Submerge the thermometer probe under the water. The probe should not be  in direct contact with the bottom of the bucket. You may have to tape the thermometer to the gauge rod.
  3. Take note of the temperature, that of the water.  A single  temperature measurement has error equal to  be LC/4, where LC is the thermometer’s   smallest division, which you will record. LC = 1 degree Celsius. Note : Your first measured temperature will be at room temperature, defined  as T1 in the graph discussed  below.   After the initial  set up is complete, get a second thermometer and measure room temperature, holding the glass column by the end opposite the bulb.  Below, after you turn the range to high, you will measure the pressure as soon as the temperature reaches pre-measured room temperature.
  4. ROOM TEMPERATURE MEASUREMENT ANDS CALIBRATION:     With another  

                 thermometer, measure the temperature of the room. Turn on the electric range

        to high. Observe the rise in the temperature of the water.  When the temperatures reaches

        room temperature,  record T1 and P1.  In  the pressure measurement, your error in a single
        measurement would be L.C./4, where L.C. = smallest division on the pressure gauge. Please look

        closely at the gauge to record the least count.

        Note that the pressure may be offset from the  true value at the room temperature of the water.

        Thus you must subtract or add the  magnitude of the difference between the room temperature

        reading T1  ands   reading and   atmospheric pressure PATM, in  PSI   (pounds per square inch.) .  If

        the initial reading is above PATM ,  then you must subtract;  if  the initial reading is below PATM , 

        you must add.

        The error will be  enlarged by this extra step involving the offset. . Since you are subtracting two
         pressures directly  to  get the offset , we may  use  formulas  from   previous labs for  difference or 
         sum errors. That  formula  is ·LC/4,. Thus  the total  error can be written as (1 +   )·LC/4,
         where LC = the  smallest division on the pressure   gauge.  These will be the  vertical error bars for
         the graphs  discussed below. Using LC = 0.5   psi, we  get a total error for a   single pressure

         measurement of  0.3  psi.

  1. Record the pressure  at the intermediate points of  40 0C ,  60 0C,  and 80 0C. Record the exact values of the pressure and temperature. Remember, each  single  temperature measurement has an error equal to  be LC/4, where LC is the thermometer’s   smallest division, which you will record.  LC = 1 degree on the thermometers we used.
  2. Record the pressure at the maximum water temperature which should be about 100 0C. determining  the error as discussed in 7.
  3. Calculate the slope m from all 5 data points. Graphing methods discussed in class and hand outs  will guide you through the process of computing m = rise/run. Then write the equation for the line in point slope form 
    P - P1 = m*(T - T1).  Find the T intercept by setting P = 0.   Note that P is the y-axis and T is the x-axis in this case.  Calculate the T intercept in     in degrees oC.    Find the error  in your final temperature value according to this formula:  


    ΔT1



    Note the first term,  ΔT1,  is equal to LC/4 = ¼ degrees = 0.25 = 0.3 degrees rounded off. The error Δm  =  (mMAX – mMIN) /2 is discussed in the graphing handouts.  Refer to step 4 for ΔP1. Also note  mBEST and (P1)BEST are the values of the graphed slope lying   somewhere between mMAX  and  mMIN  and the single “best” measurement of P1, respectively.  Compute the percent error between your computed Tbest and the theoretical value- 273 oC.  Compare this percent error with the error ΔT. Which is larger?
  1. Plot the best-fit line of T vs. P in Excel using the data points. Note that T is the y-axis and P is the x-axis in this case. (Be careful !) Calculate the percent error between the T-intercept and the theoretical value. 
    9.   FInally,  can you think of a way to get better agreement between the hand computation and excel ? Is there a better choice for t1 and P1 that is  not necessarily a data point?  Check back soon for a hint to the answer!

Questions (4 points each.) Short answers.
1. What would happen to the kinetic energy, theoretically,  if the molecules of a gas if its temperature could reach 0 K? Why is this a theoretical impossibility according to Quantum Physics? Explain in a paragraph and site your source. 

2. What is the lowest achieved temperature in Kelvin ? The answer is not zero. Please site your internet reference and explain in a paragraph how the lowest achieved temperature was achieved, using known concepts from our studies to date.

3. Compute the  product of the numerical answer to the last question and the temperature of the interior of the sun? (i.e. What answer do you get when you multiply them together?) Please site sources for additional data used.

4. You have a sample of H2Ohat happens at the triple point of water in terms of the first three phases of matter, solid, liquid and gas  ? If you increase the pressure from the pressure value of the triple point, which phase increases its presence in the H2O sample, solid, liquid or gas?  

5. What is the approximate value of the triple point temperature in 0C to the nearest hundredth place?

6. What is the letter of the correct answer? The temperature of 1 cup of water is 25 0C.  The temperature of  30 gallons of water is 25 0C. The average kinetic energy of the molecules in the cup is
(a) less than those in the  30 gallons container (b) more than those in the 30 gallon container
(c) the same