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Understand uncertainty, accuracy, and precision in measurements. Learn about percent error, significant figures, and calculations with significant figures. Boost your scientific measurement skills!
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Uncertainty in Measurements All measurements have uncertainty. • Measurements involve estimation by the person making the measurement. • Measuring devices are limited in their precision
Accuracy and Precision Accuracy – the closeness of measured values to the true or accepted value Precision – the closeness of repeated measurements of the same quantity
Percent Error • Used to compare measured values to the true or accepted value.
Percent Error Sample Problems • Calculate the percent error in a length measurement of 4.25 cm if the correct value is 4.08 cm. • The actual density of a certain material is 7.44 g/cm3. A student measures the density of the same material as 7.30 g/cm3. What is the percent error of the measurement
Counting Significant Figures Determine the number of significant figures in each of the following numbers: 0.003042 1.4030 1000 1000. 1000.00 0.060 50.0 10.47020 250. 65,321 2.00 x 102 1.004 x 105
Rounding to Significant Figures Round each of the following numbers to three significant digits: 1,566,311 2.651 x 10-3 84,592 0.0011672 0.07759
Calculations with significant figures • Find the volume of a cube that is 3.23 cm on each edge. • What is the sum of 67.14 kg and 8.2 kg? • Calculate the density of a 17.982 g object that occupies 4.13 cm3.