1. Do Now: 1.How many significant figures are in the following: a)12.001 b)0.000379 c)0.0003790 d)30100 2.Convert the following to scientific notation: a)67000 b)67001 c)0.0067 d)0.0067001

2. Rationale – In general, a calculated answer can NOT be more precise than the least precise measurement it was calculated from. Calculations with significant figures Significant Figures in addition and subtraction: Rule- The answer should be rounded to the same number of decimal places as the measurement with the LEAST number of decimal places.

3. Example – 7.85 mL +88.1 mL + 0.995 mL Step 4 – Evaluate if the answer makes sense – Double check the number of your answer has the same decimal place as the least number of decimal places of any of the numbers used in the addition and/or subtraction problem Method 1 Step 1 – Circle the measurement with the least number of decimal places. (88.1 mL) Step 2 – Add up all of the values: 7.85 mL + 88.1 mL + 0.995 mL = 96.945 mL Step 3 – Round the answer to the decimal place in the circles number: 96.9 mL

4. Example – 7.85 mL +88.1 mL + 0.995 mL Method 2 Step 1 – Setup the numbers above each other with the decimal places aligned: 7.85 mL 88.1 mL + 0.995 mL Step 2 – Perform the math 7.85 mL 88.1 mL + 0.995 mL 96.945 mL Step 3 – Look at the math problem and round the answer to rightmost decimal place that has a number in EVERY column (you can circle the column if that helps visualize it). Round to 96.9 mL (final answer) Step 4 – Evaluate if the answer makes sense – Double check the number of your answer has the same decimal place as the least number of decimal places of any of the numbers used in the addition and/or subtraction problem

5. 1.6.12 g + 1.7 g + 19.1 g 2.22 g – 3.6 g 3.12.01 g +1.0079 g + 12.01 g +1.0079 g Practice Problems

6. Rule – In calculations involving multiplication and division, you need to round the answer to the same number of significant figures as the measurement with the least number of significant figures. Significant Figures in Multiplication and Division

7. Example – 11.5 x 2.9 Step 1 – Circle the number with the fewest number of significant figures used in the multiplication and/or division. (2.9) Step 2 – Write the number of significant figures next to the circled number. (2.9) 2 sig figs Step 3 – Perform the math operation(s) 11.5 x 2.9 = 33.35 Step 4 – Round answer to the correct number of significant figures. 33 Step 5 – Evaluate the answer. Double check your final answer with the numbers used in the problem. Does the final answer have the same number of significant figures as the fewest number of significant figures used in any of the numbers in the calculation (compare again with your circled number from Step 1).

8. Practice Problems 1.15 ÷ 3 2.15 ÷ 3.0 3.112 x 33.55 x 1.7 4.6.75 x 110.2 ÷ 0.33 5.11 x 9 = 5 = 5.0 = 6400 = 2300 = 100

9. Conversion Factors A Conversion Factor is a ratio of equivalent measurements. Creating a conversion factor Step 1 – Setup an equation of two equal measurements. 1 dollar = 4 quarters Step 2 – Divide both sides of the equation by the right hand side 1 dollar = 4 quarters 4 quarters = 4 quarters Step 3 – Simplify the equation 1 dollar = 1 4 quarters Step 4 – Flip the equation if needed (the same thing as having divided both sides of the equation by the left hand side instead of the right hand side). 4 quarters = 1 1 dollar

10. Setup a conversion factor for the following: 1.Seconds in a minute 2.Milliliters in a liter 3.Kilograms in a gram Practice Problems