It is essential that chemists develop strong oral communication skills. At the undergraduate level, this requires students to build confidence in their ability to speak without a script and to utilize graphics effectively. We have developed a short activity that helps address common presentation issues such as overuse of text and reading verbatim off slides. The three-minute slide activity is an engaging exercise for the students and is easy for instructors to implement.

In place of traditional cookbook laboratory exercises, a nonmajors' chemistry course uses a demonstration-focused laboratory to understand basic chemical theories. Each student spends the lab session preparing, practicing, and learning the chemistry of two unique demonstrations. By selecting demonstrations of different concepts, the students cover the same breadth and type of themes as a traditional laboratory in a new and exciting format. Twice during the semester, students from the course prepare and present two demonstration shows as an outreach program to 3rd–5th graders at local elementary schools. The demonstration format provides the college nonscience students an active-learning experience that is able to provide motivation and generate interest. Overall, the students felt that the demonstration-focused laboratory succeeded in increasing their level of understanding of material, strengthened their interest in science, and held their interest. This pedagogy also provides purpose for studying chemical concepts and direction as students strive to explain concepts to younger children.

An inexpensive, field-portable sensor for direct, aggregate determination of aqueous petroleum hydrocarbons (PH) down to sub-ppm levels was developed. The basis of this sensor was an unusual, highly nongravimetric frequency response of 10 MHz (series fundamental) AT-cut quartz crystals when coated with rubbery silicone films. The response depended linearly and reliably on the total concentration of dissolved hydrocarbons over a range of 0.01-100 mg x L(-1) or up to aqueous solubility limits. Calibration sensitivities were measured individually for laboratory-prepared solutions of BTEX (benzene, toluene, ethylbenzene, and xylene isomers) and C6-C8 aliphatic components. Each component demonstrated a method detection limit (MDL) in the low-to sub-ppm range (benzene 10 mg x L(-1), n-hexane 0.54 mg x L(-1)) for light coatings of a commercially available poly-(dimethylsiloxane) gum (OV-1, > 10(6) g x mol(-1)) and lower MDLs for heavier coatings. Pairwise responses for the aliphatic and benzenoid standards were additive, indicating that aggregate determinations of mixtures (especially light fuels) were possible. Natural matrix interferences caused by sample turbidity and ionic strength were overcome by simple preparative methods. Fuel-spiked natural waters were determined with respect to standards and verified by gas chromatography. A 0.19 mg x L(-1) MDL for gasoline was obtained for heavy OV-1 films. Field determinations of groundwater surrounding a leaking underground fuel tank demonstrated that the sensor and method were useful for on-site PH screening. Large differences between the equilibration times of aliphatic and benzenoid components also indicated one avenue for BTEX speciation with the device.

Present methods for the determination of sulfide in wastewater are hindered by poor detection limits and extensive sample pretreatment. A less problematic method has been developed with a method detection limit of 2.5 μg L-1. With this technique, sparged hydrogen sulfide is precipitated in an acetate-supporting electrolyte by electrogenerated silver ions. Analysis of base-preserved samples was performed with no pretreatment other than volumetric dilution. Metals, halides, and nitrogen-base salts were studied as possible interferences to the method. Direct comparisons with the standard methylene blue method were made for both municipal and industrial wastewaters. The present method was found to be far less inhibited by sample turbidity.

No abstract