edited by
RONALDDELORENZO Maddle GeMgia College Cochran. GA 31014
A Specific Heat Analogy
Brother Thomas MeCullough CSC St. Edward's University Austin, TX 78704
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When first introduced into the classroom or laboratory, the concept of specific heat and its use in solving heat transfer problems can be troublesome tomany students. For one thing, there are three words needed to adequately describe specific heat: calories, degrees, and grams. Individually, none of these words offers any great difficulty. Most students have an intuitive insight and have had experiential contact with these concepts. For example, most students are aware that certain foods have a higher caloric value than others and that 100 g of hot water contain more calories than 100 g of cold water. The following analogy may offer some assistance. If you want to send a package to a friend in a distant city, the postage required will depend upon the weight of the package and the distance the package will travel. However, knowing both the. weight and the distance is not enough to enahle you to determine the postage; you must also have a postal rate which
896 1 Journal of Chemical Education
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is expressed in dollars per pound per mile. dollars (pounds)(miles) . = dollars pound mde We do a similar calculatioi when we determine the number of calories of heat that are required to raise the temperature of a water sample. ~
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=calories (grams) PC) gram "C In the United States, one postal rate covers the entire spectrum of third class mail. On the other hand, different countries have different postal rates. Likewise, different substances have different specific beats (rates). The higher the postal rate, the higher the cost to send one pound of package contents one mile. The higher the specific heat, the higher the energy requirement in calories to raise the temperature of one gram of substance one degree Celsius. Thi feature presents a collection of descriptive applications and analogies designed to help students understand some of the difficult concepts frequently encountered in chemistry. Contributions that will produce a greater appreciation and knowledge of political, religious, economic, historical and seientificaspects of life are encouraged.
