Significant Digits
Name __________________
Damon Patterson
4
Period ______
Chem Worksheet 1-6
A measuring device is only able to give a limited amount of information about the object being
measured. For example, a balance may only tell the mass of an object to the nearest 0.1 g. Limitations
in a measurement are reflected by the number of digits present in the measurement. These digits are
known as significant digits. In the example above, an objects mass may be measured as 125.2 g. The
measurement has 4 significant digits.
It can be difficult to determine the number of significant digits in a measurement when there are
zeros, so we will
employ a method for
ATLANTIC – PACIFIC RULE
counting significant
1. Start on correct side – Atlantic (decimal Absent) or Pacific (decimal Present)
digits known as the
2. Count digits starting with the first non-zero
Atlantic-Pacific rule.
3. Count all digits to the end
These rules are outlined
in the box to the right.
Example
How many significant digits are in the numbers 54,000 and
0.000420?
54,000
54,000 has 2
significant digits.
We start counting on the Atlantic side (the
decimal is absent). We start counting at the
first non-zero digit (the four) and count all
digits until the end (the five).
0.000720 has 3
significant digits
We start counting from the Pacific side (the
decimal is present). We start counting at the
first non-zero digit (the seven) and count all
digits until the end (the last zero).
0.000720
Present
Absent
Write the number of significant digits present in each of the following measurements.
1. 240 s(2 significant digits)
5. 8520. Pa(4 significant digits)
9. 2.0 g(2 significant digits)
2. 0.003 m(1 significant digits)
6. 8520 Pa(3 significant digits)
10. 75.60 L(4 significant digits)
3. 65.00 mL(4 significant digits)
7. 70 100 kg(3 significant digits)
4. 0.0480(3 significant digits)
8. 0.3006 mol(4 significant
digits)
11. 0.000 002 0 km(2 significant
digits)
12. 4.20 × 108 mg(3 significant
digits)
Do the following calculations and round the answer to the correct number of significant digits.
13. 2.15 × (3 significant digits)
14. 0.51 ÷ 0.20(3 significant digits)
15. 15 640 × 3.40(5 significant
digits)
16. 0.02 ÷ 0.01568(3 significant
digits)
19. 0.0071 + 0.015 + 1.24(4 significant
digits)
17. 6520 × 3.45 × 8.1(6 significant 20. 641.1 + 129.34 + 18.154(3
significant digits)
digits)
18. 52.18 + 1.7252( 4 significant
digits)
21. 5.15 × 103 – 1.2 × 103
(3 significant digits.)