1. Unit 2 MATH OF CHEMISTRY 2.6 Are scientists always 100% correct? AIM: How do we calculate percent error ? DO NOW: Please answer the following question Find the volume that 35.2g of carbon Tetrachloride (CCl 4) will occupy if it Has a density of 1.60 g/mL. Density = mass volume 1.60g/mL = 35.2g ? V= 22mL

2. WHAT IS PERCENT ERROR? Allows us to measure how far off we are from the theoretical (accepted) value Formula %Error = Theoretical – Experimental x 100 Theoretical Theoretical  accepted, actual, known

3. Another way you may see the formula….. Formula %Error = Actual– Measured x 100 Actual

4. ACTIVITY Directions: Use the M&M Activity worksheet to complete this part of the lesson. 1.Record your MEASURED VALUE (experimental) 2.Record the ACTUAL VALUE (theoretical) 3.Calculate the percent error.

5. LET’S TRY SOME Working in the laboratory, a student finds the density of a piece of pure aluminum to be 2.85g/mL. The accepted value for the density of aluminum is 2.699g/mL. What is the student’s percent error? Step 1. Locate theoretical and experimental values Theoretical = 2.699g/mL Experimetal = 2.85g/mL Step 2. Plug into the formula and solve %Error = 2.699g/mL- 2.85g/mL 2.699g/mL X 100

6. NEXT Complete the Percent Error Worksheet When you are done, you may work on the following: CHEMISTRY VOCABULARY JOURNAL - you will be allowed to use this on your quizzes and (some of) your exams