Significant Figures 1.All non-zero digits are significant (2.45 has 3 SF) 2.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 ( has 2 SF and has 3 SF) 4.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 has 5 SF)

5.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 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 cm cm cm = 15.5 cm

Practice m m m g g g ml ml 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 kg x 2.1 kg kg = 16 kg

g 12.4 cm 3 = g /cm 3 = 2.23 g/ cm 3

Practice ( m) (21.4 m) = m 2 = m 2 = 1.58 x 10 6 m 2 (691 g / cm 3 ) = g / cm 3 = g / cm 3 = 1.73 x 10 6 g / cm 3

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

Practice to4SF to 3SF x to3SF 7831to2SF (7.054 x 10 2 ) (6.38 x ) 6.04 x (7.8 x 10 3 )