If the density of lead is about 10 and the volume was

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Unformatted text preview: a regular solid the volume is: V = length × width × height We note that the dimensions are all in cm except the 62 mm. Convert this to centimeters. 62 mm × 1 cm = 6.2 cm 10 mm The volume is V = 20.5 cm × 9.7 cm × 6.2 cm = 1233 cm3 V = 1.2 × 10 3 cm3 (two significant figures) Substituting into the equation for mass m=d×V 11.4 g m= × 1 .2 × 10 3 cm3 = 1.4 × 10 3 g cm3 The last step in solving the problem is checking the answer. Is it reasonable in size and units. One way to check an answer is to estimate it in your head with rounded numbers. If the density of lead is about 10 and the volume was 1200 cm 3 , then the answer should be close to 12,000 g, which it is. Also the units of grams are correct for mass. •Comment When solving problems, based on an equation such as this example was, notice that we followed three steps. 1. Rearrange the equation so that the unknown quantity is by itself on one side. 2. Substitute in known quantities including their units. 3. Calculate the answer including its units. _______________________________________________________________________________ EXAMPLE 1.14 A Conversion of Volume Units How many cubic centimeters are equal to 5 m3 ? •Method of Solution The desired unit is cm3 . ? cm3 = 5 m3 Ro...
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This note was uploaded on 09/15/2009 for the course CHEM 102 taught by Professor Bastos during the Spring '08 term at Adelphi.

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