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# Chem Book Ch 2 (98% on the test)

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Louisiana State University

Chemistry

CHEM 1001

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Winter

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Ch 2 Notes from Book Global warming the gradual increase of global temperatures oGlobal temperatures affect everything from agriculture to weather and ocean levels Unit a standard agreedon quantity by which other quantities are measured extremely important in reporting and working with scientific measurements must always be includedScientific notation used to write very big or very small numbers often containing many zeros more compactly and precisely each number consists of a decimal part and an exponential partoDecimal part a number that is usually between 1 and 10oExponential part 10 raised to an exponent n To express a number in scientific notationStep 1Move the decimal point to obtain a number between 1 and 10Step 2Write the result multiplied by 10 raised to the number of places you moved the decimal pointif moved to the left the exponent is positiveif moved to the right the exponent is negativeScientific numbers reported so that every digit is certain except the last which is estimated Significant figures or digits the nonplaceholding digits in a reported measurement represent the precision of a measured the greater the number of sigfigs the greater the precision of the measurement To determine the number of significant figures in a number follow these rules1All nonzero digits are significant1Interior zeros zeros between two numbers are significant1Trailing zeros zeros after a decimal point are significant1Leading zeros zeros to the left of the first nonzero number are not significant1Zeros at the end of a number but before a decimal point are ambiguous and should be avoided by scientific notation Exact numbers have an unlimited number of significant figures Defined quantities some conversion factors such as 100 cm in 1 m In multiplication or division the result carries the same number of significant figures as the factor with the fewest significant figures we focus on significant figures Round down if the last or leftmost digit dropped is 4 or less Round up if the last or leftmost digit dropped is 5 or more

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