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16 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
2
Significant figures The number of digits reported in a measurement indicates how precise the measurement is. The more digits
reported, the more precise the measurement. The digits reported in a
measurement are called significant figures. Significant figures
include all known digits plus one estimated digit.
These rules will help you recognize significant figures.
1. Nonzero numbers are always significant.
45.893421 min has eight significant figures
2. Zeros between nonzero numbers are always significant.
2001.5 km has five significant figures
3. All final zeros to the right of the decimal place are significant.
6.00 g has three significant figures
4. Zeros that act as placeholders are not significant. You can
convert quantities to scientific notation to remove placeholder
zeros.
0.0089 g and 290 g each have two significant figures
5. Counting numbers and defined constants have an infinite number of significant figures.
Example Problem 2-9
Counting Significant Figures
How many significant figures are in the following measurements?
a. 0.002849 kg
b. 40,030 kg
Apply rules 1–4 from above. Check your answers by writing the
quantities in scientific notation.
a. 0.002849 kg has four significant figures; 2.849 ϫ 10 Ϫ3
b. 40,030 kg has four significant figures; 4.003 ϫ 10 4
Practice Problems
23. Determine the number of significant figures in each
measurement.
a. 0.000010 L
c. 2.4050 ϫ 10 Ϫ4 kg
b. 907.0 km
d. 300,100,000 g
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