Percent Error and Density What does Percent Error Sound Like? Measuring and calculating Percent Error tells us how well something was done. (ie how well you did your experiment….) Measured Value - Accepted Value Accepted value X 100 = percent Error Lets Try This Together! Measured=40.35 g Calculated= 39.25g 40.35g -39.25g 39.25g = 0.02802 x 100 = 2.8% Try on your own Measured: 25.55 g Calculated: 26.33g What do you do when it’s Negative! Measured Value - Accepted Value Accepted value X 100 = Present Error 25.55g- 26.33g x100 = -2.962% 26.33 Take absolute Value of the answer = 2.962% Ratio What are some examples of ratio’s? Density • Mass: Volume D= M V Mass Volume M D V Unit Density = g/ml Mass = g Volume = ml or cm3 Lets try this Mass: 22.6g Volume: 25 ml What is the density? Mass: 22.6g Volume: 25 ml 22.6g 25 ml Don’t Forget! 2 Sig Fig = 0.90 g/ml On your own Density: 62 g/cm3 Mass: 12.33 g 12.33g 62 g/cm3 0.19887 ~ 0.20 cm3 Division it gets flipped Unit Math: g 1 cm3 g = cm3 1 • Density = 1.869g/cm3 • Volume = 23.6cm3 (1.869g/cm3)(23.6cm3) = 44.1084 ~ 44.1 g