Significant Figures All non-zero digits are significant (2.45 has 3 SF) Zeros between (sandwiched)non-zero digits are significant (303 has 3 SF)

3. Zeros to the left of all non-zero digits are NEVER significant. (0 3. Zeros to the left of all non-zero digits are NEVER significant (0.000025 has 2 SF and 0.0000125 has 3 SF) Zeros to the right of all non-zero digits are only significant if they are also to the right of the decimal (250 has 2 SF and 250.00 has 5 SF)

Counting numbers have infinite significant figures (21 students has infinite SF) 6. Exactly defined quantities have infinite significant figures (100 cm = 1 m -both terms have infinite SF)

Practice 0.00400 1000 681.000 404.0040 3 SF 1 SF 6 SF 7 SF

Adding and Subtracting with Significant Figures The answer should have no more decimal places than the number in the problem with the least decimal places. 10.21 cm + 5.3 cm 15.51 cm = 15.5 cm

Practice 721.493 m - 508.2 m 213.293 m 7.516 g + 2.1 g 9.616 g 0.00307 ml + 0.406 ml 0.40907 ml

Multiplying and Dividing The answer must be rounded to the same number of significant figures as the number in the problem with the least significant figures. 7.83 kg x 2.1 kg 16.443 kg = 16 kg

27.634 g 12.4 cm3 = 2.228548387 g /cm3 = 2.23 g/ cm3

Practice (73814.69 m) (21.4 m) = 1579634.366 m2 = 1580000 m2 = 1.58 x 106 m2 (691 g / 0.0004000cm3) = 1727500 g / cm3 = 1730000 g / cm3 = 1.73 x 106 g / cm3

Rounding Select the place you want to round to: 26.3495 Look at the place after the one you want to round to: 26.3495 If < 5 round down If ≥ 5 round up 26.35

Practice 705.3998 to 4SF 0.00638114 to 3SF 6.037 x 10-8 to 3SF 705.4 (7.054 x 102) 0.00638 (6.38 x 10-3) 6.04 x 10-8 7800 (7.8 x 103)