OBJECTIVE: The student shall demonstrate an understanding of dilution and their ability to problem solve by accurately determining an unknown concentration that will require (unknown to the students), a serial dilution.
PURPOSE: Serial dilution, though encountered rarely in daily life, is frequently encountered in biology and chemistry. This lesson gives students an understanding of serial dilution, which will be used in the Sperm Dilution lesson and can be used in other lessons using sea urchin fertilization.
SET: Yesterday, we saw how a simple spectrophotometer can be used to help us determine the unknown concentration of a substance. I also asked a more complicated question of how accuracy could be improved. Today you will be on your own to solve a concentration problem.
MODEL: 1) Review yesterday's lesson. 2) Show list of available materials to solve their problem.
STRUCTURED PRACTICE: Go over answers to yesterday's unknowns. Did they get the correct answer? Answer any questions they have about the assignment.
GUIDED PRACTICE: Use the Socratic method to help lead students to an answer.
CLOSURE: We worked with colored dye today, but this could just as easily have been a new miracle drug or a poisonous substance. How do you think this new skill could be useful to the researcher?
NOTES: This is a difficult lesson that many adults would have trouble with. Once they learn it though, they have a very powerful research tool at their disposal.