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Slide 1 of 48 Measurements and Their Uncertainty 3.1 3.1 Section 3.1-1 Scientific Notation and % Error.

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Presentation on theme: "Slide 1 of 48 Measurements and Their Uncertainty 3.1 3.1 Section 3.1-1 Scientific Notation and % Error."— Presentation transcript:

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2 Slide 1 of 48 Measurements and Their Uncertainty 3.1 3.1 Section 3.1-1 Scientific Notation and % Error

3 © Copyright Pearson Prentice Hall Slide 2 of 48 3.1 Measurements and Their Uncertainty On January 4, 2004, the Mars Exploration Rover Spirit landed on Mars. Each day of its mission, Spirit recorded measurements for analysis. In the chemistry laboratory, you must strive for accuracy and precision in your measurements.

4 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 3 of 48 Using and Expressing Measurements How do measurements relate to science? 3.1

5 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 4 of 48 3.1 Using and Expressing Measurements A measurement is a quantity that has both a number and a unit. Measurements are fundamental to the experimental sciences. For that reason, it is important to be able to make measurements and to decide whether a measurement is correct.

6 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 5 of 48 3.1 Using and Expressing Measurements In scientific notation, a given number is written as the product of two numbers: a coefficient and 10 raised to a power. The number of stars in a galaxy is an example of an estimate that should be expressed in scientific notation.

7 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 6 of 48 Accuracy, Precision, and Error How do you evaluate accuracy and precision? 3.1

8 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 7 of 48 3.1 Accuracy, Precision, and Error Accuracy and Precision Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured. Precision is a measure of how close a series of measurements are to one another.

9 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 8 of 48 3.1 Accuracy, Precision, and Error To evaluate the accuracy of a measurement, the measured value must be compared to the correct value. To evaluate the precision of a measurement, you must compare the values of two or more repeated measurements.

10 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 9 of 48 3.1 Accuracy, Precision, and Error

11 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 10 of 48 3.1 Accuracy, Precision, and Error Determining Error The accepted value is the correct value based on reliable references. The experimental value is the value measured in the lab. The difference between the experimental value and the accepted value is called the error.

12 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 11 of 48 3.1 Accuracy, Precision, and Error The percent error is the absolute value of the error divided by the accepted value, multiplied by 100%.

13 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 12 of 48 Accuracy, Precision, and Error 3.1

14 © Copyright Pearson Prentice Hall Measurements and Their Uncertainty > Slide 13 of 48 3.1 Accuracy, Precision, and Error Just because a measuring device works, you cannot assume it is accurate. The scale below has not been properly zeroed, so the reading obtained for the person’s weight is inaccurate.

15 © Copyright Pearson Prentice Hall Slide 14 of 48 3.1 Section Quiz 1. In which of the following expressions is the number on the left NOT equal to the number on the right? a.0.00456 x 10 –8 = 4.56 x 10 –11 b.454 x 10 –8 = 4.54 x 10 –6 c.842.6 x 10 4 = 8.426 x 10 6 d.0.00452 x 10 6 = 4.52 x 10 9

16 © Copyright Pearson Prentice Hall Slide 15 of 48 3.1 Section Quiz 2. Which set of measurements of a 2.00-g standard is the most precise? a.2.00 g, 2.01 g, 1.98 g b.2.10 g, 2.00 g, 2.20 g c.2.02 g, 2.03 g, 2.04 g d.1.50 g, 2.00 g, 2.50 g

17 © Copyright Pearson Prentice Hall Slide 16 of 48 That’s All Folks ! ! !


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