Absolute Zero Lab

IRL Lab:

The rationale for this lab is that as you decrease temperature, the pressure will decrease.  Absolute zero is the temperature at which the pressure is zero.  We will determine this by extrapolating from some data points.

Directions:

1. Set up your graph in Landscape, and make every square be 10 oC in the x direction, and the vertical scale, every square is 25 Torr.

2. Your  x-axis will go from -390 oC to 110 oC if one of your temps is above 100 oC, or you can go -400 oC to +100 oC if not.  Your y axis goes from 0 to 1000 Torr.

3. Plot your points

4. Add error bars with a straight edge.  Use a piece of folded paper, and mark where the top and the bottom and the middle is so you can be consistent.

5. Add an extrapolation to the x-axis through the points that is a best fit line.

6. Add the steepest extrapolation line to the x-axis that goes through all of the error bars, and doesn't miss any.  Typically, but not always, this goes through the lowest error bar on the lowest temp point, and the highest error bar on the highest temp point.  Just make sure you are not missing any error bars in the middle.

7. Do the same for the least steep extrapolation to the x-axis.

8. Read and record the x-intercepts of all three lines, to give you a lowest extrapolation, best guess extrapolation, and a highest extrapolation.

9. Write a conclusion citing data that does two things:

   1. State your results.  (Lowest, best guess, and highest)

   2. State Lord Kelvin's value (and if this were your IA, you would actually give a citation - a bibliographic reference) and citing data, prove that it either does fall in the range of your extrapolation, or does not fall within that range.

Your completed lab will include the following:

1. A proper data table with units and uncertainties.  (See below)  All the numbers for a particular variable have the same precision.  (Decimal place)

2. A proper graph - points and error bars - titled with axes labeled.

3. Your three extrapolations

4. Your conclusion

(Lame) Pandemic Lab:

The rationale for this lab is that as you decrease temperature, the pressure will decrease.  Absolute zero is the temperature at which the gas exerts no pressure on the walls of its container.  We will determine this by extrapolating from some data points.

Directions:

1. Click Here to run the Gas Properties PhET

2. Click on "Ideal".  Above the thermometer pull the menu down to make it read oC.  Below the pressure gauge, pull it down to read kPa.

3. Initially there are no particles present, so below the pump click the right button, and drag the pump up and down three times to inject three pumpfulls of light particles.  

4. Cool it to about 0 oC by sliding the slider on the bucket below the sim down.  Record the temperature in a data table.  Notice how the pressure jumps around a bit.  This is because there are only about 145 particles in the whole sim.  If there were a mole of particles, it would be rock steady.  This is OK, let's use these natural fluctuations in pressure to generate trial to trial uncertainty.  

5. To take a data point of  pressure, hit the pause button in the lower left, record the pressure, un-pause for a second, and pause again, record the pressure.  Do this to create data for five trials.  If this were an IA, we might want more trials, but five is enough for now.

6. Now you have one temperature, and five pressure data points.  Click the play button, and use the slider below the sim to heat it up to about 30 oC.  Gather five trials of pressure the same way we did before.  Then do the same for about 60 oC, 90 oC, and 120 oC.  You now have five temperatures and for each temperature you have five trials of pressure.  The temperatures don't have to be exact, just within maybe 5 oC of the target temperature.  (I.e. 32 oC is fine for the 30 oC data point.)  Whatever the temperature actually is, record it in your data table.

7. In your data table, create a column that contains the average of the trials, and the uncertainty of the trials.  ((high-low)/2)  Left to right, the columns could be "Temperature oC", "Average Pressure kPa", "Pressure Uncertainty kPa", "Trial 1", "Trial 2", "Trial 3", "Trial 4", "Trial 5" - as long as you indicate somewhere that the trials are pressures in kPa.

8. Notice that the uncertainty bubbles about, but there is no real trend.  Because Google Sheets does not make it easy to make different sized error bars for each point, let's just average the uncertainties (no real basis for doing this, we just need error bars, and I don't want you to hate me too much)

9. Create a scatter graph of pressure vs temperature.  Make the x axis go from -350 oC to 150 oC with major gridlines every 25 oC and minor every 5 oC.  Add a trendline to the points.  (The X-intercept is what?)  Make the points 1 point in size, and give them error bars that are constant and the size of the average uncertainties in the trials.

10. Copy and paste your data table into the Google Doc you are going to submit, and resize your graph to take up the whole area of the spreadsheet, covering up the numbers.  (Make it as big as possible, leaving room for the edit menu on the right...)  Make sure at this point that it has a title, and the axes are labeled with units and quantities.  

11. Add a steepest and least steep line to your graph using the draw tool.  These lines are the steepest and least steep lines that you can make that stay inside all the error bars.  They need to go entirely across the plot frame, intersecting the X axis.  Screenshot this into your Goooogle Doc that you are turning in.  Keep in mind that if you click on the graph behind the lines, it will move the graph in front of the lines and they will be hidden.  For this reason it is prudent to have the lines stick over the edge of the graph somewhere, so you can bring them to the foreground again.  This is why we screenshot them.  Someday, Google sheets will let you directly order layers, but it doesn't yet as I write this.

Screen shots to clipboard:

11. 1. Chromebook:  ctl-shift-screenshot (The key above the 6) This brings up a window, then click "copy to clipboard", and paste it into your doc with ctl-v

    2. Mac: ctl-shift-command 4 - paste with command-v into your doc

    3. PC: shift-windows-s, paste with ctl-v into your doc

12. Read where the trendline meets the X-axis, and where the highest extrapolation (steepest line) hits the X-axis, and the lowest extrapolation (least steep line) hits the X-axis.  Estimate these down to the nearest degree.  It helps to Zoom in on the picture or the graph by changing the Zoom% to 200%

13. Answer these questions in your own words:  What were your results.  Cite your best fit line's X-intercept, and the highest and lowest extrapolations.  Cite what absolute zero is in oC, and do two things, 1. Compare it to the value you got for the best fit line, and 2. State whether it falls within your max and min extrapolations.

Videos: