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Lecture Free Teaching: Properties of Solutions 2010 KSTA Conference Lisa Devillez Marshall County High School
Lecture Free Teaching (LFT) • Note-making as “homework” / Vodcasting foundational lectures • improves textbook reading skills • classroom discussion focused on student questions • more class time for labs • more time for "advanced" problems • Active Learning!
Lecture Free Teaching (LFT) • Clear and concise objectives • Notes • Homework • Tests • Mastery learning & standards-based grading are complementary LFT
Lecture Free Teaching (LFT) • Class time • Opportunity for student feedback • Collection of active learning activities • Limit “lectures” (ie., passive instruction) in both frequency and time
Solutions • The perfect “unit” for LFT and developing lab skills • Narrowed scope of objectives based on difficulties of former students • Selected / modified labs to address all of the objectives
Objectives • 5.1 Define units of concentration, mass percent, ppm, mole fraction, molarity, and molality, and be able to calculate each from appropriate data. • 5.2 Be able to convert a concentration from one unit to the other. • 5.3 Be able to calculate solution concentration for single and serial dilutions. • 5.4 Describe the effect of solute (or solvent) concentration on boiling point and freezing point. Be able to calculate any of these effects from concentration data for nonelectrolyte solutes.
The Labs: General Format • Prepare a solution of the assigned concentration. • Measure property for 5 standard solutions (teacher-prepared) and student solution. • Graph property vs. concentration for the standards • Use equation for trend line and measurement for student solution to verify its concentration
The Labs: Documentation • Data Tables • Standards graphs • Trend line • Correlation value (R2) • Calculations • Verification of student solution concentration • % error
Refractometry: Snell’s Law “The determination of the concentrations of sugar solutions by Laser Refractometry” Hughes & Jelks JCE November 1988
Colligative Properties: Freezing point • Assigned 2.0M 100mL • Standards in molalities
Spectroscopy: Beer’s Law • 5mL glucose solution & 5mL Benedict’s • Spec 20; 730nm; distilled water blank