• The student will use a calculator-based laboratory (CBL) with a graphing calculator in the single point mode  to collect data with a pH probe. 
• The student will use a CBL and graphing calculator in the monitor input mode to collect data with a conductivity probe.
• The student will construct tables of their data (both pH and conductivity).
• The student will construct histograms of their data (both pH and conductivity).
• The student will define the term electrolyte.
• The student will give examples of electrolytes.
• The student will classify solutions as electrolytes or non-electrolytes using data gathered in class.
• The student will classify substances as acids, bases, or neutral after measuring the pH using data gathered in class.

Extension/Exploration Objectives:

• The student will explain the importance of electrolyte balance in homeostasis.
• The student will identify the health dangers associated with electrolyte loss.

• SI-H-B3, SI-H-B4, SI-H-A3
• LS-H-G1, LS-H-F2
• PS-H-D2, PS-H-C2
• D-7-H, P-2-H

• one 90-minute class period or two 50-minute class periods

• proper measuring techniques 
• pH (acid, neutral, base) 
• conductivity
• CBL, graphing calculator, pH probe usage, conductivity probe usage 
• interpretation of data
• developing descriptions, explanations, and graphs 
• predicting outcomes 
• lab safety 
• correct use of lab equipment
• lab reports
• scientific method

• CBL (computer based laboratory) 
• TI-83 Plus graphing calculator 
• pH probe 
• conductivity probe
• TI adapter cable
• DIN adapter 
• 6 fifty (50) mL beakers 
• waste beaker
• 40mL each of tap water, bottled water, orange juice, Gatorade, Powerade, and Kool-aid
• DI water 
• goggles 
• apron 
• kimwipes 
• paper 
• pen
• ruler
• graph paper
• label stickers

• medical application
• research and development
• chemical industry 
• health and wellness
• personal knowledge
• decision-making

• Cooperative groups of 3 students (Captain, Recorder, and Materials Manager).  The responsibilities of each student are outlined in the procedure.

• lack of knowledge of equipment 
• incorrect data collection procedures 
• lack of accuracy in measurement techniques
• incorrect laboratory technique 
• breaking safety contract
• graphing and labeling errors
• lack of knowledge and understanding of pH and conductivity

• Group or individual lab report: Students complete a formal lab report which includes data tables, graphs of results and analysis questions. 
• Performance based practicum: Students demonstrate proper usage of the CBL, graphing calculator, pH probe, and conductivity probe by successfully completing related experiments at lab stations. 
• Research project: Have students complete a research project on any of the topics listed in the connections section of Exploration and Extension. 

Laboratory Safety

• Safety concerns
• Teacher will reiterate to students that they signed a safety contract at the beginning of the semester. 
• Specific safety reminders for this lab include: 
• Goggles and lab aprons must be worn at all times.
• Acids burn the skin and eyes.
• Do not taste any of the solutions.
• Probes should only be placed in the approved solutions.
• Assign cooperative group roles
• Remind students that they are to work with their group ONLY.
• Inform students of lab material locations.
• Hand out the laboratory procedure and direct students to read and follow lab procedures within their cooperative groups. 
• Check that students have changed the position of the toggle switch on the conductivity probe according to the lab procedure instructions.

1.   All group members obtain and wear goggles. 

2.   Materials Manager will obtain six (6) 50mL beakers and label one of each:  tap water, bottled water, orange juice, Gatorade, Powerade, and Kool-Aid. 

3.   Materials Manager will fill each of the beakers with approximately 40 mL of each specified solution. 
 

Part I--pH 

4.   The Captain will prepare the CBL for pH measurements 

A. Prepare the pH Electrode for data collection. 

1. Plug the pH Amplifier into the adapter cable in Channel of the CBL System.  Connect the pH  Electrode to the pH amplifier. 
2. Use the link cable to connect the CBL System to the TI Graphing Calculator.  Firmly press in the cable ends.

B. Turn on the CBL unit and the calculator.  Start the CHEMBIO program and proceed to the MAIN MENU. 

1. Select SET UP PROBES from the MAIN MENU. 
2. Enter "1" as the number of probes. 
3. Select pH from the SELECT PROBE menu.
4. Enter "1" for the  channel number.

C. Prepare the CBL and calculator for calibration. 

1. Select USE STORED from the CALIBRATION menu. 
2. Select COLLECT DATA from the MAIN MENU. 
3. Select SINGLE POINT from the DATA COLLECTION menu.

A.  Remove the pH Electrode from the storage bottle.  Rinse the tip of the electrode thoroughly with the DI water. 
B.  Place the tip of the electrode into the first liquid.  Submerge the electrode tip in the liquid to a depth of 3-4 cm. 
C.  When the reading displayed on the CBL screen stabilizes, press ENTER to begin sampling. 
D.  After 25 seconds, the pH value will appear on the calculator screen.  The Recorder will record this value in the first data table--Data Table 1 (round to the nearest 0.01 pH unit). Clean the probe with DI water after placing in each liquid.
E.  Press ENTER, then select YES to repeat the measurement. 
F.  Press ENTER, then select YES to repeat the measurement for all other liquids being tested. 
G.  When all of the liquids have been tested, select NO to return to the MAIN MENU. 
H.  Select QUIT to exit the CHEMBIO program.

Part II--Conductivity

7.  The Captain will prepare the CBL for conductivity measurements: 

A. Prepare the Conductivity Probe for data collection. 

1. Plug the Conductivity Probe into the adapter cable in Channel 1 of the CBL System.  Set the selector switch on the Conductivity Probe to 0-20,000 microsiemens. 
2. Use the link cable to connect the CBL System to the TI Graphing Calculator.  Firmly press in the cable ends.

B. Turn on the CBL unit and the calculator.  Start the CHEMBIO program and proceed to the MAIN MENU. 

1. Select SET UP PROBES from the MAIN MENU. 
2. Enter "1" as the number of probes. 
3. Select Conductivity from the SELECT PROBE menu.
4. Enter "1" as the channel number.

C. Prepare the CBL and calculator for calibration. 

1. Select USE STORED from the CALIBRATION menu. 
2. Select H 0-20000 MICS from the CONDUCTIVITY menu. 
3. Select COLLECT DATA from the MAIN MENU. 
4. Select MONITOR INPUT from the DATA COLLECTION menu.  Follow the directions on the calculator screen to allow the system to warm up, then press ENTER.  The conductivity reading (in microsiemens) is displayed on the screen of the TI calculator.  No readings are stored when using the MONITOR INPUT mode.

A.  Rinse the tip of the probe thoroughly with the DI water. 
B.  Place the tip of the conductivity probe into the first liquid.  Submerge the probe tip in the liquid so that the hole in the tip is completely submerged in the liquid. 
C.  Once the conductivity reading has stabilized (stops moving), the Recorder will record the reading from the calculator in your second data table--Data Table 2  (record the conductivity in whole numbers). 
      **Note:  CBL has only three digit display.  Do not record data from the CBL in your table. 
D.  To avoid contaminating the solutions, rinse the probe with clean, distilled water after each test.  Blot the outside of the probe end dry with a tissue or paper towel.  It is not necessary to dry the inside of the hole near the probe end. 
E.  When all of the solutions have been tested, press the + button on the calculator to return to the MAIN MENU.  Select QUIT to exit the CHEMBIO program.

10.  Materials Manager will dispose of the tested solutions in an appropriate manner. 
 

Analysis

11.  When all of your measurements have been taken and recorded in your Data Tables, the Recorder will ensure that all group members have written the pH and conductivity readings in their individual Data Tables.  Each group member will individually construct a histogram of the data in each table on a separate sheet of graph paper.  The pH histogram should be labeled Figure 1 and the Conductivity histogram should be labeled Figure 2. 

12.  Using the Data Tables and Figures, each student should answer the analysis questions for the lab on an individual basis.

1.  Define the term "electrolyte" and give at least 2 examples of chemical elements that would be found in an electrolytic solution.

2.  Which of the solutions tested were electrolytes?

3.  Which solution has the greatest conductivity?  Which solution has the least conductivity?  Explain your answers.

4.  Based on the CONDUCTIVITY measurements that you obtained in this lab, which drink would be the most beneficial to you to replace electrolytes after working out?

5.  Which solutions were acids?  Which solutions were bases? Which solutions were neutral?

6.  Which solution was the most acidic?  Which solution was the most basic?

7.  Based on the CONDUCTIVITY and pH measurements that you obtained in this lab, which drink would be the most beneficial to you to replace electrolytes after working out?

8.  Pedialtye, an electrolyte replacement solution marketed to treat small children suffering from diarrhea and vomiting, has a conductivity reading of 5685 microsiemens.  Without reading the product information labels,  to what would you attribute this increase in conductivity?
 
 

Scoring Rubric:  That Deep Down Body Thirst
 

Criterion 1:  Laboratory Safety  __________ x 2 = ____________

0 :  Laboratory safety policies and procedures were not followed at all times.
|
X
|
X
|
3 :  All laboratory safety policies and procedures were followed.
 

Criterion 2:  Laboratory Technique  __________  x 1 = ____________

0 :  Lab equipment was not used properly or cleaned after experiment.
|
1 :  Lab equipment was used incorrectly, but lab station was cleaned.
|
2 :  All equipment was used correctly, but lab station was not cleaned.
|
3 :  All equipment was used correctly and lab station was cleaned after the experiment.
 

Criterion 3: Lab Report--Data Tables  __________  x 3 = ____________

0 : No Data Tables 
|
1 : One Data Table 
|
2 : Two Data Tables recorded, but incorrectly (missing one or more components)
|
3 : Data Tables  recorded correctly (titles, units, headings) 
 

Criterion 4:  Lab Report--Figures  __________  x 3 = ____________

0 :  No Figures
|
1 : One Figure drawn 
|
2 :  Two Figures drawn, but incorrectly (missing one or more components)
|
3 :  Figures drawn correctly (titles, units, labels, x and y values correct, accurate)
 

Criterion 5:  Lab Report--Analysis Questions   ___________  x 2 = ____________

0 :  No Analysis Questions Answered
|
1 :  Two or more analysis questions answered incorrectly
|
2 :  All analysis questions answered correctly but questions not written
|
3 :  All analysis questions copied and answered correctly
 

Criterion 6:  Lab Report--Overall Appearance  __________  x 2 = ____________

0 :  More than two components missing
|
1 :  Two components missing
|
2 :  One component missing
|
3 :  Headings, objectives, procedure, data and calculations, conclusions
 

Criterion 7:  Cooperative Group Effort  __________  x 3 = ____________

0 :  Two or more group members not cooperating and not performing specified tasks
||
1 :  Group members working independently and not together
|
2 :  One group member not cooperating or performing his task
|
3 :  All group members working together and performing their specified tasks
 

Criterion 8:  Timeliness   __________  x 1 = ____________
 

0 :  Turn in after school begins one or more days late
|
1 :  Turned in following day before school begins
|
2 :  Turned in after class on due date
|
3 :  Turned in on time on due date
 
 

Subtotal = ________________   / 50 (one bonus point given)

Johnson, Robyn L., Holman, Scott and Holmquist, Dan D.  Water Quality with CBL.  Vernier, 1999. 

Holman, Scott and Masterman, David.  Biology with CBL. Vernier, 1998.