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04CHM114_handout_nutshell

04CHM114_handout_nutshell - CHEM 114 FALL 2000 C A Angell...

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CHEM 114, FALL 2000 C. A. Angell Chemistry in a Nutshell About chemistry and science Chemistry is a science, the central science according to many. This means that every discipline whether more mathematical than chemistry or less so, needs to have some of chemistry to be understandable. Chemistry is deeply involved in many of the major problems that threaten the present civilization , and some appreciation of this chemistry by the general public will be needed if the problems are going to be resolved. Chemistry deals mostly with changing one form of matter into other forms. Chemistry has a long history, most of it unscientific, driven by the desire to change cheap things into gold. In producing the changes of matter by chemistry, energy is often used. Take for example the conversion of ores into metals using furnaces. On the other hand, in our production of power on a large scale (power stations) or small scale (batteries) we use the changes in matter forms (like combustion reactions) to produce energy. The search for understanding by Science uses the Scientific Method, which itself needs to be understood. It usually "works well", but rarely produces gold. Measuring things Science is different from other human activities because it deals with precise ideas that can be checked out and proven or disproven, eventually to everyone's satisfaction (though it sometimes takes a very long time). One proves things in science by measuring things and showing that the measured properties are the ones predicted by the idea (theory). Theories are produced by men to explain laws of nature in terms more fundamental than those used to describe the laws. Laws of nature are what we call it when the results of many measurements show the same thing happening every time. To measure things one needs measuring standards . These are agreed-upon units of measurement. International Science has settled on S. I. (Science Internationale - it's in French) units. These deal with the fundamental dimensions of length, mass and time. Students need to know what are the units in the SI system and how to convert them to other units. Things to be measured in science go from the miniscule to the humongous, i.e. from extremely small to extremely large. We need to use scientific notation in numbers to deal with this problem. In measurements, there is accuracy , on the one hand, and precision on the other. We want you to know the difference, and how to express it. While you may not be sure of the accuracy of a measurement, you find out quickly whether it is precise or not, by repeating it a few times. The significant figures in the measurement are the ones in the answer that come up every time, plus the last one which fluctuates. Learn the rules for combining significant figures in a calculation.
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Properties like density are obtained by combining measurements of different type, here mass and volume. The density is sort of conversion factor . You use it to convert mass to volume. Each substance has a characterisitic density at room temperature, and it is different for the different states of matter. Likewise, the property
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