1. Sig Figs

2. 5.23 cm Significant Digits (Sig Digs) 5.230 cm
Significant Digits include:
measured certain digits
last estimated digit
(uncertain)
5.23 cm
do not overstate the precision
5.230 cm

3. Significant Digits 0.0003700400 m All nonzero digits are significant.
Captive Zeroes between two significant digits are significant.
Leading Zeroes at the beginning of a number are never significant.
Trailing Zeroes are significant at the end of a number IF there is a decimal. 2. 3. 4.
Captive
0’s
Leading
Exact numbers are infinitely significant. How many boy students in here? Plus girls? How many sig figs?
Trailing
How many sig digs?
200
(1)
200.
(3)

4. 5. Counting numbers (counting things) and defined constants (like Pi) have an infinite number of significant figures. (also numbers involving conversions)

5. + & – x & ÷ Significant Digits 3.48 g + 2.2 g = 5.68 5.7
round answers to keep the fewest decimal places
round answers to keep the fewest sig digs
3.48 g g =
5.68
5.7
x & ÷
6.40 cm x 2.0 cm =
12.8 13

6. Quick Quiz!
1. How many sig digs are in each number?
250.0 mL
4.7 x 10–5 kg mg m 4 2 2 4
2. Round the answer to the correct sig digs.
(i) m x m
(ii) g ÷ 3 mL
(iii) g g
(iv) g – 2.0 g ÷ 4 cm3
809 m2
40 g/mL
35.1 g
0.3 g/cm3
1.0 g