2. measured certain digits. last digit is estimated, but IS significant. do not overstate the precision 5.23 cm 5.230 cm Significant Figures (Sig Figs) (uncertain)

3. 1.All nonzero digits are significant. 2.Captive Zeroes between two significant figures are significant. 3.Leading Zeroes at the beginning of a number are never significant. 4.Trailing Zeroes are significant at the end of a number IF there is a decimal. 0.0003700400 m Significant Figures 0’s

4. round answers to keep the fewest decimal places round answers to keep the fewest significant figures Significant Figures + or – x or ÷ 3.48 g + 2.2 g = 6.40 cm x 2.0 cm = 5.68 5.7 12.8 13

5. 1. How many sig figs are in each number? (i) 250.0 mL (ii) 4.7 x 10 –5 kg (iii) 34000000 mg (iv) 0.03400 m 2. Round the answer to the correct sig figs. (i) 34.5 m x 23.46 m (ii) 123 g ÷ 3 mL (iii) 23.888897 g + 11.2 g (iv) 3.00g – 2.0 g ÷ 4 cm 3 4 2 2 4 809 m 2 40 g/mL 35.1 g 0.3 g/cm 3 Quick Quiz! 1.0 g