In this paper we describe the construction of a simple spectrophotometer intended for use as a capstone circuit for an electronics laboratory exercise. Students in the undergraduate laboratory have learned basic circuitry and are now able to read a schematic and construct an instrument that has practical applications in chemical analysis. A simple LED is used as the source and is easily changed to correspond to different species being studied. Detection is accomplished through the use of one of three signal transducers (a photoresistor, a photodiode, or a photodarlington) and a current-to-voltage converter. A box lined with black felt is used to shield the spectrophotometer from ambient light. This spectrophotometer shows excellent Beer-Lambert law linearity over a large concentration range and has been used in the laboratory to determine the concentration of a metal cation in solution on the basis of a calibration curve. Of the transducers used, the photoresistor showed the best response at multiple wavelengths with error in concentration determination not greater than 6%. Through the building and testing of this circuit, the students can visualize applications of electronic circuitry.

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This article describes an approach to general chemistry that involves teaching chemical concepts in the context of two thematic laboratory modules: environmental remediation and the fate of pharmaceuticals in the environment. These modules were designed based on active-learning pedagogies and involve multiple-week projects that dictate what content is taught and in which order the content is presented. Students were expected to design experimental procedures, analyze data, and communicate their results. A description of the two laboratory modules is included along with a week-by-week description of the student experience.

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