1. Significant Figures Homework: Working with Numbers handout # 1 – 13 Significant Figures handout # 1 - 10

2. What is the length of the following?

3. Significant Figures Definition: all the known values from a measurement including a last estimated digit

4. Determining the # of Sig Figs in a measurement 1.Is the decimal present or absent? 2.Begin at the appropriate ocean side of the measurement 3.Move to the first non- zero digit 4.Count all digits moving across

5. Recall the measured value from earlier: How many significant digits are there in our measured value?

6. Do Now: Indicate the number of significant figures in the following measurements: 0.00734 cm 3 _____ 510 mL_____ 510. mL_____ Homework: Significant figures worksheet # 11 - 32

7. Addition and subtraction with Sig Figs The answer has only as many decimal places as the measurement having the least number of decimal places. Procedure: 1. line up all measurements by decimal points 2. perform the calculation on your calculator 3. draw a line down next to the least decimal place 4. round your answer off the answer to the digit to the left of the line

8. Example: Given: 2 H 2 + O 2 → 2H 2 O If 4.0318 g of H 2 are combined with 32.0 g of O 2, how many grams of H 2 O are formed? 4.0318 + 32.0____

9. Example Given: 2 H 2 + O 2 → 2H 2 O How many grams of hydrogen are consumed when 108.2 g of H 2 O are formed form the reaction of 96.00 g of O 2 ?

10. Multiplication and Division Rule: The solution to a multiplication or division problem can only have as many significant figures as the starting measurement with the least number of significant figures. Procedure: 1. perform the calculation on your calculator 2. count the number of significant figures in the starting measurements 3. round your answer off the answer to the least number of significant figures

11. Example: A student found the mass of an object to be 50.11 grams and the volume of the object to be 22.0 mL. What is the density of the object?

12. Example: Gold has a density of 19.320 g/mL. If a piece of gold has a volume of 14.8 mL, what is the mass of the object

13. Example: What is the mass of 75.2 mL of mercury? (density of mercury is 13.546 g/cm 3 )