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12 Chapter One Chemical Foundations A measurement always has some degree of uncertainty. the tenths of a pound place; in the second case, the uncertainty occurs in the thousandths of a pound place. Suppose we weigh two similar grapefruits on the two devices and obtain the following results: Bathroom Scale Balance Grapefruit 1 Grapefruit 2 1.51b 1.51b 1.476 Ib 1.518 Ib Uncertainty in measurement is discussed in more detail in Appendix 1.5. Do the two grapefruits have the same mass? The answer depends on which set of results you consider. Thus a conclusion based on a series of measurements depends on the cer- tainty of those measurements. For this reason, it is important to indicate the uncertainty in any measurement. This is done by always recording the certain digits and the first un- certain digit (the estimated number). These numbers are called the significant figures of a measurement. The convention
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This note was uploaded on 12/13/2010 for the course CHEM 2301 taught by Professor Bill during the Spring '10 term at South Texas College.

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