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# Pressure, Temperature and Absolute Zero Calculations

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Procedure

1. Take a gas piston from the Glassware shelf and place it on the workbench.

2. Take a balance from the Tools shelf and drop it directly onto the gas piston. Record the mass of the empty piston.
Mass of empty piston 111.420 g

3. Select one of the gases from the Chemicals shelf and fill the gas piston with 100 mL of the gas. Record the mass of the piston plus gas.
Chose CH4 Methane new mass is 111.486 g

4. Remove the gas piston from the balance.

5. Open the Data window and click on the gas piston. Click the Pushpin icon on the blue bar of the Data window to lock its display to the gas piston.

6. Take a thermometer and pressure gauge from the Tools shelf and drop them on the gas piston.

7. Take a heating plate from the Tools shelf and drop it on the gas piston.

8. Open the Properties window and click on the heating plate. In the Properties window turn the heating plate on and turn the dial to set the heat to around 200 watts.

9. Watch the temperature of the gas in the piston increase and the gas volume in the piston rise.

10. Once the temperature of the gas has reached nearly 200C, remove the piston from the heating plate.

11. The temperature will begin to fall and the gas volume displayed in the Data window will decrease. Record pairs of temperature and volume data every 10 degrees C or so, until the temperature has returned to room temperature.

Temperatures Gas Volume
190 157.32
180 153.91
170 150.39
160 146.78
150 143.21
140 139.89
130 136.66
120 133.90
110 129.43
100 126.18
90 123.49
80 120.19
70 116.63
60 113.53
50 110.15
40 106.47
30 103.08
21 100.00

NOTE: This is best accomplished by working in pairs, with one person calling out the data values and the other writing them down.

12. Next, take a constant temperature bath from the Tools shelf and place it on the workbench.

13. Using the Properties window, set the bath to dry ice.

14. Drag the bath and drop it onto the gas piston.

15. When the temperature of the gas falls to nearly -70C, Remove the gas piston from the constant temperature bath.

16. Record the temperature and volume of the gas in the piston at every 10C increment or so as it warms back up to room temperature.

Temperature Gas Volume
-70 68.91
-60 72.66
-50 75.85
-40 79.14
-30 82.65
-20 85.83
-10 89.46
0.02 92.85
10 96.25
21 100.00

Assignment

1. Record the formula of the gas you selected to run the experiment.
CH4 Methane

2. What is the constant pressure at which this experiment was run?

3. The molecular weight of the gas is shown in the Data window. Calculate the number of moles of gas from the measured masses of the empty piston and the piston plus gas.

4. Use a spreadsheet to construct a graph of the recorded data with the temperature, in degrees C, on the x-axis and the volume, in mL, on the y-axis.

5. Find the slope and intercept of the straight line fit to the data points. In Excel, the slope is given by the function SLOPE (y values, x values) and the intercept is given by the function INTERCEPT (y values, x values). Record these values.

6. Calculate the value for absolute zero, in degrees Celsius, from the equation developed in the background section of the lab manual:

T0 = -(intercept / slope)

7. The accepted value for absolute zero is -273.15C. Calculate the percent error of your results according to:

%error = |T(experimental) - T(accepted)| / |T(accepted)| * 100

8. In designing the experimental procedure, should you aim to use a large or small initial volume of air? Explain why.

9. In designing the experimental procedure, should you try to control the heating/cooling rate of the apparatus to be slow or fast? Explain why.

10. This experiment extrapolates the behavior of an ideal gas down to coldest possible range. In reality, the gas would condense into a liquid as it approaches absolute zero. Does this affect the conclusion reached regarding the value of absolute zero?

11. Amazingly enough, researchers have recently been able to cool a low-density gas of sodium to nano-Kelvin temperatures, and -273.15C is indeed the limit that is approached. At these low temperatures, the gas is dominated by quantum mechanical effects.

https://brainmass.com/physics/temperature/pressure-temperature-and-absolute-zero-calculations-227322

#### Solution Summary

Experimental Data obtained from a real practical lab is manipulated and used in order to extract key information about absolute zero. Other questions are also answered regarding ideal gases and absolute zero.

\$2.19

## Simulation Investigating Isobaric, Isochoric, & Isothermal Processes

Perform a simulation investigating three special processes - isobaric (constant pressure), isochoric (constant volume), and isothermal (constant temperature) - that can be derived from the ideal gas law. The simulation is found at Background Info 1. The simulation allows you to vary the pressure for an isobaric process, the volume for an isochoric process, and the temperature for an isothermal process. The simulation shows how the system goes from one equilibrium state to another and the work that is done on or by the system, and how heat flows into or out of the system.

The variables are:
V1 = initial volume, dm3 (dm = decimeter = 10 cm)
V2 = final volume, dm3
P1 = initial pressure, kPa (absolute; that is, measured against vacuum)
P2 = final pressure, kPa
T1 = initial temperature, K
T2 = final temperature, K

Heat flow: into system (red arrow points right)
out of system (red arrow points left)

Work done: on system (blue arrow points up)
by system (blue arrow points down)

Experiment 1:
Isobaric (constant pressure) Process
P1 = P2 = 100 kPa

Experiment 2:
Isochoric (constant volume) process
V1 = V2 = 1.00 dm3
Following a procedure similar to the one in Experiment 1, show how these results illustrate the Ideal Gas Law for the special case of constant volume.

Experiment 3:
Isothermal (constant temperature) p
Following a procedure similar to the one in Experiment 1, show how these results illustrate the Ideal Gas Law for the special case of constant temperature.

The isothermal case deserves a special mention, because at first glance it seems to be just plain wrong. Everybody knows that when you squeeze a quantity of gas, the volume goes down and the pressure goes up; but the temperature ALSO goes up. Ask any diesel mechanic! So what's going on here?

Answer: Either the volume is decreased (pressure increased) so slowly that the heat can escape, and the temperature remains a constant, OR the system is compressed to its new, smaller volume, and allowed to cool to its original temperature, before the new pressure is measured. Which is definitely a lab experiment, and not an industrial process.

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