Preliminary Evaluation of a Video Program on pH Calculations The success of any approach to learning in chemistry ultimately Lie4 in the ability of students to synthesize mathematical skills with chemical concepts. This paper evaluated the 35-min program, "Acids and BasesIpH Calculations,"' which is designed for students who have little or no understanding of p H calculations. This production differs from most video programs by incorporating (1) "in-house quizzes" for positive reinforcement of newly learned skills, (2) flashing symbols and numbers to emphasize subject matter, (3) direction for reviewing specific aections if students fail to answer questions correctly, (4)systematic rest periods to reduce learning fatigue, (5) a general conceptualization of acids and bases, and (6) detailed demonstrations an writing scientific notation, calculating log and antilog values, and calculating pH and hydrogen ion concentrations. A successful method for teaching conversions of pH to hydrogen ion concentrations is shown in Example One. The viewer is presented with one line a t a time until helshe see8 the entire example. Example One
Video Screen pH = 6.50 -log Hf = 6.50 +log HC = -6.50 = (-6.00) (-0.50)
Narrative Topic stating the problem. converting the syrnhol "p" to words. obtaining the proper sign for the term "log." separating values into integer and decimal parts.
+
(-6.00)
+ (-0.50)
antilog (+log H t ) = antilog [(-7.00)
mantissa must he positive and characteristic may he negative. T o obtain positive mantissa while keeping the value of the expression constant, add and subtract one.
+ (0.50)] using antilogs to obtain numerical values. rewriting into standard reporting f o m .
While deviring a method of evaluation, we became aware that studems accumulate knowledge from pre- nnd wt-testing, talking with peers, and viewing this video tape. In the table, the n,w "Attempts" is defined as any written statement or mathematical calculation. The row "Correct" denotes a positive trend between problems attempted and competence to obtain correct answers, which indicates learning by a majority of students. Surprisingly, during past-testing, students were observed to spend more time and effort working with newly learned skills than with older ones;2this is supported by the small percentage difference in pre- and post-testing attempts for identifying acid and base solutions. The row "correct" also suggests this video program is a successful education tool.
Number of Questions Population PreRost Test Attempts Problems Attempted in Pre-Tests Problems Attempted in Post-Tests Correct Correct Answers in Pre-Tests Correct Answers in Post-Tests
Calculating PH
Calculating Hydrogen Ion Concentrations
Identifying Acid and Base Solutions
Calculating Log Values
59%
38%
89%
86%
This program is available for viewing and discussion by those interested in producing and evnlunting learning effectiveness of video progiarnr designed for traditionally drffirult learning areas for students.
'This program is produced and owned by the author and Media One, Belmont, Calif. 94002. 2
Observations performed by proctors. Author interviewed students after post-testing.
Indian Valley Colleges Novato, California 94947
316 / Journal of Chemical Education
Manus B. Monroe
