Volume 4, Issue 2

An Exercise in Sampling: The Effect of Sample Size and Number of Samples on Sampling Error
Original Research
A simple and fast exercise is outlined to show science students the importance of determining the size of a sample and also the quantity of sample in order to minimize sampling error and improve accuracy, and to achieve a desired error.
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World Journal of Chemical Education. 2016, 4(2), 45-48. DOI: 10.12691/wjce-4-2-3
Pub. Date: June 18, 2016
14227 Views3488 Downloads1 Likes
Practical Chemistry of Long-Lasting Bubbles
Original Research
In this report, an experiment is described in which high school students investigate long-lasting bubbles of their own design. The features of the soap bubbles change depending on their chemical composition. To investigate the students’ original bubbles, the chemical structures and features of the ingredients are considered when choosing the detergent, polymer, and other chemical components. Soap bubble containing sucrose, sodium alkyl ether sulfate (AES)-detergent and poly(vinyl alcohol) (PVA) (or partially hydrolyzed poly(vinyl alcohol) (PVAAc)) often maintains a spherical shape on various solid surfaces, including concrete, asphalt, tile, and grass after landing. Students hypothesize that the low surface tension of the long-lasting bubble is not the sole reason for its long lifetime on various solid surface. The mechanism behind the extended lifetime is discussed through experiments involving the surface tension and lifetimes of the bubbles under various humidity conditions. Students encounter basic chemistry through the experiment, which can be adopted into the chemistry curriculum.
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World Journal of Chemical Education. 2016, 4(2), 32-44. DOI: 10.12691/wjce-4-2-2
Pub. Date: May 18, 2016
52924 Views10511 Downloads1 Likes
Quantitative Analysis of Copolymers and Blends of Polyvinyl Acetate (PVAc) Using Fourier Transform Infrared Spectroscopy (FTIR) and Elemental Analysis (EA)
Original Research
Fourier transform infrared spectroscopy (FTIR) is one of the most important instrumental techniques used to study the molecular structure of organic polymers. As part of our efforts to increase instrumental use in the undergraduate chemistry laboratory we have developed a quantitative FTIR experiment for use in our quantitative and instrumental analysis courses. The objective of the experiment is to determine the percent composition of PVAc in copolymers and blends with polyethylene (PE) and n-vinyl pyrrolidone (PVP). We report on the experimental methods used and the results obtained on examining the quantitative FTIR and elemental analysis of a series of ethylene-vinyl acetate (EVAc) copolymers. The EVAc copolymers ranged from 10% to 70% PVAc. Copolymers and blends of n-vinyl pyrrolidone-polyvinyl acetate (PVP/PVAc) ranging from 20% to 80% PVAc were also analyzed.
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World Journal of Chemical Education. 2016, 4(2), 25-31. DOI: 10.12691/wjce-4-2-1
Pub. Date: May 17, 2016
55642 Views9198 Downloads5 Likes1 Citations