1. Significant Digits Unit 1 – pp 56 – 59 of your book Mrs. Callender

2. Significant Digit Rules 1. All nonzero numbers are significant. 1.345 g has 4 significant digits. 2. Zeros between nonzero numbers are significant. 1.05 g has 3 significant digits.

3. Significant Digit Rules 3. Zeros before nonzero numbers but after the decimal place are NOT significant. 0.0033 g has 2 significant digits. 0.00 33 g the zeros are PLACEHOLDERS 4. Zeros after the decimal AND after nonzero numbers are significant. 1.500 g has 4 significant digits. 1.5 00 g the zeros are significant.

4. Significant Digit Rules 5.Zeros both at the end of a number but to the left of a decimal points is NOT significant. 1,000 L has 1 significant digit 1,000 L the zeros are PLACEHOLDERS

5. What about 200 red cars? Is there a measuring device for cars? Counting numbers have an infinite number (∞) of significant digits. Conversion factors are exact: 1 inch = 2.54 cm This has ∞ number of significant digits

6. Rounding rules for number 5. Math: when rounding with a 5 the number would get “rounded up”. 4.5 rounds to 5 In Science…… Odd numbers: 1,3,5,7,9 Round up with 5 Even numbers: 0,2,4,6,8 No rounding with 5 Round 1.35 cm to 2 significant digits. Round 1.45 cm to 2 significant digits. 1.4 cm

7. Addition and Subtraction Add/Subtract then round to the data with the fewest number of DECIMAL places. 24.5001 cm 123.45 cm + 0.378 cm 148.3281 cm 3 decimal places 2 decimal places 4 decimal places Answer can only have 2 decimal places. Round 148.3281cm to 148.33 cm * *

8. Multiplication and Division Multiply/Divide then round to the data with the fewest number of Significant Digits. 24.5001 cm X 0.378 cm 9.2610378 cm 2 3 sig. digs 6 sig. digs. Answer can only have 3 significant digits. Round 9.2610378 cm 2 to 9.26 cm 2 * *