CHEMISTRY STUDY GUIDE

Students can learn how to read the periodic table and carry out some rudimentary chemical reactions with this primer.

Gebhart, who has a bachelor’s degree in chemistry and a master’s in science education, covers a narrow range of chemistry topics in this slender volume. He starts by displaying several partial versions of the periodic table of the elements, each introducing a new piece of data, including chemical symbols, atomic number, atomic weight, and valence electrons. He then offers a brief history of chemistry, touching on ancient concepts of the four elements and atomistic philosophy, medieval alchemy, the dawn of modern chemistry in the recognition that elements combine into compounds in fixed ratios, the rise and fall of phlogiston, Dmitri Mendeleyev’s creation of the periodic table, J.J. Thomson and Ernest Rutherford’s discovery of the atomic nucleus, and Niels Bohr’s detection of quantized energy levels in electron orbitals. With these few scraps of theoretical background recapped, the author then presents problem sets on the basics of stoichiometry, the accounting system that spells out the amount of substances that will go into and come out of a chemical reaction. These straightforward quantitative problems—“How many grams of Cu will react with 200 grams of AgNO3 in a chemical reaction with the balanced equation: Cu + 2AgNO3 = 2Ag + Cu(NO3)2?”—involve reading numbers off of the periodic table and performing simple calculations with them. The book’s second part consists of 15 experiments that are about as elementary as laboratory chemistry gets, requiring students to mix a few ingredients in a water solution and see what happens. Gebhart gives detailed instructions on weighing the various reagents, measuring the temperature and pH of solutions, and ascertaining the amount of the resulting product to see how it tallies against theoretical predictions.

Gebhart’s well-written historical introduction to chemistry ably conveys the excitement of the field to neophytes. (“Rutherford described his amazement at this discovery as being the same as if he had fired a cannon at a tissue and the cannon ball bounced back at him off the tissue.”) The author’s problem sets will give students a good workout, albeit in a very limited repertoire of calculations. Unfortunately, there are typos and errors in the text—the atomic weight of argon is listed in Gebhart’s periodic tables as 83.90 instead of its correct value of 39.948—and the laboratory exercises have major methodological flaws. In one experiment, students are asked to measure the pH of 10-molar hydrochloric acid, but acid that concentrated is beyond the measurement range of standard pH meters. In others, students are told to dry and weigh an insoluble precipitate to determine the percentage yield of a reaction, but not to wash the precipitate first. As a result, other compounds from the solution will cling to the precipitate and increase its final dry weight. And in a third set of experiments, students are invited to weigh a reaction solution to gauge the percentage yield of a reaction, but that instruction is nonsensical because all the reagents and products are together in the solution and the weight cannot change regardless of the yield. Some students may want to look for a more comprehensive guide.

A lively but sometimes-confused introduction to chemistry theory and practice.