Heat Evolution and Electrical Work of Batteries as a Function of Discharge Rate: Spontaneous and Reversible Processes and Maximum Work
Robert J. Noll and Jason M. Hughes; J. Chem. Educ., 2018, 95, pp 852−857.
This article describes an experiment in which students compare the enthalpy change of the useful electrical work to the heat lost from the electrochemical reaction in batteries. AA alkaline batteries are installed in a battery holder and connected to a heater resistor and sensors. The apparatus is suspended in a Dewar flask and the water is stirred gently at 200 rpm. The potential, current, and temperature are measured over a period of 30 minutes. The students use a Current Probe and a Voltage Probe connected to a computer running through a LabQuest Mini to measure the work output of the battery. The waste heat produced is measured calorimetrically using a Stainless Steel Temperature Probe. This activity combines concepts from electricity, electrochemistry, and thermodynamics in one experiment.
Measuring the Force between Magnets as an Analogy for Coulomb’s Law
Samuel P. Hendrix and Stephen G. Prilliman; J. Chem. Educ., 2018, 95, pp 833−836.
The authors describe a simple demonstration to illustrate the relationship between charged particles as described by Coulomb’s law. They use a Dual-Range Force Sensor mounted on a LEGO® platform. The sensor is connected to a computer with a Go!Link and monitored with our free Logger Lite software. A neodymium magnet is attached to the end of a screw. It is installed where the hook or bumper would normally go in the sensor. A second neodymium magnet is mounted to another LEGO® piece that is mounted on the same LEGO® platform. Attractive and repulsive forces can be demonstrated by switching the orientation of one of the magnets. The force between the magnets is plotted as a function of distance using the Events with Entry mode of data collection. This plot represents a Coulomb’s law force between charged particles and would be useful when teaching ionization, bonding, intermolecular forces, lattice energy, and PES (photoelectron spectroscopy).
Using Open-Source, 3D Printable Optical Hardware To Enhance Student Learning in the Instrumental Analysis Laboratory
Eric J. Davis, Michael Jones, D. Alex Thiel, and Steve Paul; J. Chem. Educ., 2018, 95, pp 672−677.
The authors describe the ability to use 3D printing technology to construct analytical instruments. They also discuss how to make the components of an absorbance spectrometer. Various mounts, posts, and slits are printed on a 3D printer are mounted on a platform with lenses and diffraction gratings with light sources and detectors. Even cuvette holders are fabricated. Common full-absorption spectra and Beer’s law plots are done with copper (II) sulfate solution. The results are compared to those from a Go Direct® SpectroVis® Plus Spectrophotometer. The plots of absorbance vs. wavelength and absorbance vs. concentration from the 3D-printed spectrometer compare favorably with those produced by the SpectroVis Plus.
Flexible Experiment Introducing Factorial Experimental Design
Penny Snetsinger and Eid Alkhatib; J. Chem. Educ., 2018, 95, pp 636−640.
The goal of this activity is to provide students with the opportunity to design an experiment that studies the effect of activated carbon on dyes. Students select dyes to study as well as conditions to vary such as pH, salinity, water hardness, and time of contact between the dye and the carbon. The experiment lasts multiple weeks to provide ample time for the students to vary experiment conditions and to analyze their results. Additionally, students use various analytical statistics and techniques to evaluate the outcome of their experiments. They also employ a factorial experiment design that allows them to simultaneously vary more than one variable. They used a Beer-Lambert plot to spectrophotometrically determine the concentration of dye left in the solution after exposure to the activated carbon. Students use a Go Direct® SpectroVis® Plus Spectrophotometer in this experiment.
Physicians as the First Analytical Chemists: Gall Nut Extract Determination of Iron Ion (Fe2+) Concentration
Mary T. van Opstal, Philip Nahlik, Patrick L. Daubenmire, and Alanah Fitch; J. Chem. Educ., 2018, 95, pp 456−462.
This article describes a guided inquiry activity that measures the iron in drinking water, using oak gall nut extract. This activity is geared toward students who are interested in medical careers. The idea is to use a naturally occurring substance to react with the iron ion in a solution and to form a colored solution from which the iron concentration can be determined. The students create standard Beer-Lambert plots of absorbance vs. concentration, then measure the absorbance of the gall-iron solution to determine the concentration of the iron ion. In this experiment students use a Go Direct® SpectroVis® Plus Spectrophotometer.
Measuring Yeast Fermentation Kinetics with a Homemade Water Displacement Volumetric Gasometer
Richard B. Weinberg; J. Chem. Educ., 2018, 95, pp 828−832.
This article describes how to build a volumetric gasometer from simple equipment such as plastic bottles and tubing. The students then use the device to measure the volume of carbon dioxide produced while sugar is metabolized by yeast. As the CO2 is produced the water in one bottle is displaced into a second bottle. The rate of metabolism is measured by timing the amount of water displaced. The activity is appropriate for students from middle school well into college and describes how to use the experiment with different age groups. Some of the inspiration for this activity came from Experiment 12A, “Respiration of Sugars by Yeast” from our Biology with Vernier lab book and “Sugar Metabolism with Yeast” from our lab book Investigating Biology through Inquiry.