MHS Chemistry
Thermometer Calibration
Introduction
In this activity we will be determining the correction factor for a
spirit thermometer. We will base this correction on the original
basis for the centigrade temperature scale.
Temperature scales should be based on two temperatures that are easily
reproducible in any lab. The fahrenheit scale is based on the lowest
temperature that can be reached with a mixture of snow, ammonium chloride,
and alcohol (called 0 degrees), and average human body temperature (called
100 degrees). According to legend, Mr. Fahrenheit did not sample
the temperature of many people (he used his wife!), so his 100 degree mark
is a little high. More likely, the 100 degree mark was adjusted to
make the melting point of ice an even 32 degrees F, and the boiling point
of water was 212 degrees F.
The centigrade scale was designed to be more easily repeatable by people
in other labs (eventually, Mrs. Fahrenheit died, and became unavailable
for checking the accuracy of thermometers). The freezing point of
pure water was set at 0 degrees C, and the boiling point of pure water
(at standard atmospheric pressure) was set at 100 degrees C. These
two conditions are relatively easy to reproduce in our chemistry lab.
It is recognized the "C" as a label means "degrees Centigrade."
Thermometer Notes: Never rest a thermometer on it's bulb.
Never lay a thermometer flat. Never let a thermometer roll.
Never leave a thermometer leaning in a beaker. Always use rubber
stoppers and glycerin.
Procedure
-
Obtain a thermometer from the rack in front of the class. Make sure
that the column of fluid has not separated.
-
Place the thermometer in a split rubber stopper as demonstrated, then immerse
the bottom inch or so in slushy ice water. When the temperature has
steadied, record it in the data table below.
-
Immerse the thermometer in a beaker of boiling water. When the temperature
has steadied, record it in the table below. Don't put your thermometer
away until after analysis part 1.
Data
|
Reading |
Actual Temperature |
|
Freezing Point |
_______________ |
_______________ |
C |
Boiling Point |
_______________ |
_______________ |
C |
Analysis - part 1
-
Plot a graph of "Actual Temperature" vs. "Readings." Make the scales
big enough to cover the entire range of the thermometer. This should
be a proper graph.
-
Draw a straight line going through both points.
-
Determine the equation for the line, with the form A = mR + b.
"A" is the actual temperature, "R" is the reading, "m" is the slope of
the line, and "b" is the A-intercept.
-
Attach a label to your thermometer that has the two points you graphed
(R, A), or the equation from #3. Use a sharpie pen so this label
lasts all year (ask your teacher to borrow a sharpie pen).
-
What is the actual temperature when your thermometer reads 55.1 C?
-
What is the actual temperature when your thermometer reads 119.3 C?
-
What is the actual temperature when your thermometer reads -26.4 C?
Analysis - part 2
-
Plot a graph of "Degrees F" vs. "Degrees C." Use the freezing point
and boiling point of water in each scale for your points. This should
be a proper graph, with "F" on the y-axis and "C" on the x-axis.
-
Draw a straight line going through both points.
-
Determine the equation for the line, with the form F = mC + b.
"F" is the Farenheit temperature, "C" is the centigrade temperature, "m"
is the slope of the line, and "b" is the F-intercept.
-
What is the Farenheit temperature when the actual temperature is 55.1 C?
-
What is the Farenheit temperature when the actual temperature is 119.3
C?
-
What is the Farenheit temperature when the actual temperature is -40.0
C?
What to Pass In
-
This sheet.
-
The graph, completed as described in "Analysis - part 1."
-
A sheet of paper with your work and answers to 3, 5, 6, & 7 in "Analysis
- part 1." For the equation of the line, you may chose to show the
work on the graph.
-
The graph, completed as described in "Analysis - part 2."
-
A sheet of paper with your work and answers to 3 - 6 in "Analysis - part
2." For the equation of the line, you may chose to show the work
on the graph.
-
Of course, remember the usual title stuff and neatness requirements.
[Thermometer Calibration score sheet][Chapter
2 Notes][MHS Chem page]