Chemistry For Dummies
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In chemistry, you often use exponential notation, which is simply using exponents to express a number. Scientific notation is a specific form of exponential notation that uses a power of 10 and a number between 1 and 10. Here's the format, where A is between 1 and 10 and B is an integer:

A × 10B

When you do calculations with measurements, you must make sure that your answer suggests no greater precision than was present in the original measurements. Here are some guidelines for writing your answers in scientific notation:

  • For addition and subtraction: Use exponential notation to express both numbers using the same power of 10, and then do the math. Round the sum or difference to the same number of decimal places as held by the measurement with the fewest decimal places. If your answer isn't in scientific notation (the first number in your answer isn't between 1 and 10), convert as needed.

  • For multiplication and division: Express both numbers in scientific notation so you can clearly see how many significant figures each number has. Round the product or quotient to the same number of significant figures as held by the measurement with the fewest significant figures.

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John T. Moore, EdD, is Regents Professor of Chemistry Emeritus and Coordinator of STEM Activities at Stephen F. Austin State University. He is the author of Chemistry For Dummies and coauthor of Biochemistry For Dummies.

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