Equipment:
* pH Sensor
PASPORT (PS-2102)
6507A)
|
ScienceWorkshop (CI-
* Computer Interface:
PASPORT: Xplorer GLX (PS-2002) | Xplorer
(PS-2000) | USB Link (PS-2100A) | PowerLink (PS2001)
ScienceWorkshop: 500 Interface (CI-6400)
|
750 Interface - SCSI (CI-6450)
|
750 Interface USB (CI-7650)
* 5 dixie cups (small beakers or plastic cups may
also be used) and a Test Tube Rack.
* Wash bottle filled with distilled water and large
beaker (or use a sink), to rinse off the pH sensor
between measurements.
* Solutions: gatorade, Coca-cola black, Full
Throtle, Sobe lean, milk, and Distilled Water.
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Equipment Setup:
1. Label each of the dixie cups with the names of
the various solutions.
2. Pour approxiamtely 10 ml of each solution into
the respective, labeled test tube.
3. Set wash bottle and waste beaker close by so that
the pH Sensor can be easily rinsed between readings.
Software Setup:
1.
Click on one of the links below to download a
pre-configured DataStudio file for this pH experiment,
and then open the file.
PASPORT users: Windows (.zip file) or Macintosh
(.sit file)
ScienceWorkshop 500 users: Windows (.zip file) or
Macintosh (.sit file)
2.
Connect the pH sensor to the USB link or Xplorer
(PASPORT users), or to the 500 interface
(ScienceWorkshop 500 users).
Additionally, for ScienceWorkshop 500 users –
associate the pH sensor with the interface in the
Experiment Setup window (double-click or drag).
3.
The PASPORT pH sensor typically does not need to
be calibrated; its accuracy is approximately ± 0.5 pH
units. If better accuracy is needed, or to calibrate
the CI-6507A pH Sensor, refer to DataStudio’s online
help menu for specific calibration instructions.
Data Collection Procedure:
1.
Place the pH Sensor into the first test tube
(solution #1) so that the solution just covers the tip
of the probe.
2.
Click the Start button ( ) to begin collecting
data. Because the preconfigured DataStudio file has
been prepared for manual sampling, the Start button
will change to a Keep ( ) button.
3.
Watch the digits display for the pH reading to
stabilize, then click the left side of the Keep button.
4.
A dialog box like the one shown below will appear
and allow you to enter a value for solution #. Enter
"1" and click OK. Notice the graph and table will
update automatically.
5.
Remove the pH Sensor from the test tube and
thoroughly rinse it with distilled water before
measuring the next solution.
6.
Place the pH Sensor into the second test tube
(solution #2) and repeat the steps described above to
record the second pH measurement. Continue in this
manner until all ten solutions have been measured, then
click the right side ("Stop" ) of the Keep button.
Data Analysis:
1.
Scale the axes to fit the data using the Scale to
Fit button ( ) in the Graph toolbar.
2.
Observe how many substances registered below 7 on
the pH scale, at or near 7, or above 7. Use the data to
classify the substances as acidic, basic, or neutral.
Record these observations in a data table like the one
shown below.
Data Table:
Name of
substance
Sobe Lean
Distilled
water
Coca-cola
black
Full
throttle
Gatorade
Milk
Solution
color
Pink
Clear
pH
3.30
7.05
Acid, base,
or neutral
acid
Neutral
Brown
3.64
Acid
Yellow
3.43
Acid
Orange
White
3.24
6.95
Acid
Neutral
Conclusions and Extensions:
1. Were more of the test substances acidic or basic?
How can you tell?
2. Does the color of the solution determine its pH
level?
3. What was the pH of distilled water? Why is this
value significant?
4. A local pond had a pH reading of 6 but then it
measured 4 after a recent rain storm. By what factor
did its acidity increase? What likely caused the pH
level change?
5. In order to increase the pH of a solution, what
kind of substance (acidic, basice, neutral) must be
added?
6. Why is pH important to all living things?
7. Explain the role of a buffer in a living system.