Modifications are presented for the iodine clock reaction to introduce the concept of activity and to help students better appreciate molecular aspects of chemical equilibrium. The addition of an unreactive salt affects the activity of the reactants in the iodine clock reaction. The difference in activity affects how long the iodine clock reaction…

Spectroscopy is an integral part of chemical research, and the operation of any spectroscopic instrument is critical in chemical education. This study presents a low-cost, do-it-yourself (DIY) style spectrophotometer system that can be adapted for UV--vis spectrophotometry, fluorimetry, and atomic emission spectroscopy applications. The DIY system…

The dissolution of cobalt­(II) chloride in an appropriate binary alcohol solvent yields an equilibrium mixture, consisting of the differently colored octahedral (pink in color) and tetrahedral (blue in color) cobalt­(II) coordination complexes, which can exhibit a brilliant and reversible pink-to-blue color transition over a ~10 °C window - i.e.,…

A major challenge when designing new experiments for the general chemistry laboratory is introducing students to the necessary techniques while keeping the experiment engaging and accessible. This work presents a new multiweek activity designed to introduce students to advanced instrumentation in the form of high-performance liquid chromatography…

This research paper aims to propose a novel didactic sequence inspired by an historical/epistemological study of the evolution of spectroscopy and in particular of colorimetry. The working principles of the historical color comparators and the visual color matching method, first proposed by Duboscq, stimulated us in the development of a five-step…

A chemistry laboratory experiment is described to introduce undergraduate college students to membrane separation technology. This experiment combines a simple nanowire membrane fabrication and visually indicated molecule separation. The membrane is produced via coprecipitation synthesis followed by a filtration assembly process, which can be…

The amount of protein in complex matrices such as food products is an important characteristic, at both a nutritional and a pedagogical level. There are several methods available for protein quantification, from simple UV absorption to mass spectrometry. The most common are based on the interaction of the proteins with colored compounds followed…

Conventional mobile phone colorimetry usually utilizes the RGB color mode to measure concentration of solutions, but the paper entitled "Determining the Amount of Copper(II) Ions in a Solution Using a Smartphone" proposes the use of hue ("H") to measure the concentration. It is pointed out that the "H" value increases…

Quinacridone red and violet are visually different colors, an observation confirmed by their visible reflectance spectra and CIE L*a*b* coordinates. However, their IR spectra are extremely similar. Though chemically identical, the two quinacridones are polymorphs. In this experiment, designed for and tested by nonscience majors, the pigments are…

Photochemical reactions are the reactions that are induced by light. Many of these reactions are found in natural processes, including photosynthesis and the formation and decomposition of ozone in the atmosphere. Classroom demonstrations are effective in enhancing students' learning and retention. Herein, we have developed a simple demonstration…

A simple demonstration adaptable to classroom conditions is presented, which involves the preparation of raffle tickets using filter paper and the solution of selected fluorophores. With an appropriate dilution, the text written on the tickets is not visible to the naked eye; however, it becomes readable once put under a UV lamp. Besides being a…

Practical experiments enhance students' understanding of basic concepts and promote deep learning experiences in chemistry. The smartphone application of Lab4Chemistry was utilized to replace colorimeters with smartphone camera sensors. Low-cost and readily available materials, including anthocyanin (fresh red cabbage) and common kitchen…

The following activity was developed to allow students to actively participate in and measure the kinetics of a multistep process. Each group of students is given a stack of blank coloring pages, each with a rainbow design printed on it. Each student in a group is given a different color crayon and colors in their portion of the picture before…

The "Golden Penny" demonstration is a popular experiment that involves treating copper coins with chemical reagents to form brass, an alloy of copper and zinc that has a golden color. Reported here is a very simple modification for forming golden color on copper coins that does not require the use of chemical reagents. Instead, golden…

A mixture of salt water and isopropyl alcohol is immiscible, forming two separate liquids with the organic layer on top and aqueous layer on bottom. When universal indicator is added to such a mixture, all of the indicator compounds in the universal indicator preferentially dissolve in the alcohol--except for phenolphthalein at high pH. Mixtures…