Presentation on theme: "Using and Expressing Measurements"— Presentation transcript:
1 Using and Expressing Measurements Scientific MeasurementsChapter 3Section 1
2 Vocabulary Measurement Scientific notation Accuracy A quantitative description that includes both a number and a unit.Scientific notationAn expression of numbers in the form m x 10n, where m is equal to or greater than 1 and less than 10, and n is an integer.AccuracyThe closeness of a measurement to the true value of what is being measured.
3 Vocabulary Precision Accepted value Experimental value Describes the closeness, or reproducibility, of a set of measurements taken under the same conditions.Accepted valueA quantity used by general agreement of the scientific community.Experimental valueA quantitative value measured during an experiment.
4 Vocabulary Error Percent error Significant figure The difference between the accepted value and the experimental value.Percent errorThe percent that a measured value differs from the accepted valueSignificant figureAll the digits that can be known precisely in a measurement, plus a last estimated digit.
5 Key Questions How do you write numbers in scientific notation? How do you evaluate accuracy and precision?Why must measurements be reported to the correct number of significant figures?
6 State Standard Measure with accuracy and precision. Convert within a unitUse common prefixes such as milli-, centi-, and kilo-Use scientific notationDetermine the correct number of significant figures.Determine the percent error from experimental and accepted values.Use appropriate metric/standard international (SI) units of measurement for mass (g); length (cm); and time (s).
7 Scientific Notation Hope Diamond It has 460,000,000,000,000,000,000,000 carbon atoms.Each carbon atom has a mass of g.
8 Scientific NotationIn scientific notation, the coefficient is always a number greater than or equal to one and less than ten.The exponent is an integer.
9 Scientific Notation carbon atoms in the Hope diamond 460,000,000,000,000,000,000,000 = 4.6 x 1023mass of one carbon atomg = 2 x 10-23The number 10 raised to an exponent replaced the zeros the preceded or followed the nonzero- numbers.
10 Scientific NotationWhen writing numbers greater than 10 in scientific notation, the exponent is positive and equals the number of places that the decimal point has been moved the left.6,300,0006.3 x 106Numbers less than one have a negative exponent.8 x 10-6
11 Scientific Notation Multiplication Division Multiply the coefficients and add the exponentsDivisionDivide the coefficients and then subtract the exponent in the denominator from the exponent in the numerator.
12 Scientific Notation Addition and Subtraction The exponents must be the same.The decimal points must be aligned before you add or subtract the numbers.
13 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.
15 Accuracy, Precision, and Error To calculate error:To calculate percent error:
16 Significant FiguresMeasurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation.
17 Significant FiguresA measured value’s uncertainty is expressed by its ________ digit.Final, last, rightmost
18 Determining Significant Figures in Measurements Every nonzero digit in a reported measurement is assumed to be significant.24.7 meter, 3 significant figures0.743 meter, 3 significant figures714 meters, 3 significant figures
19 Determining Significant Figures in Measurements Zeros appearing between nonzero digits are significant.7003, four significant figures40.79, four significant figures1.503, four significant figures
20 Determining Significant Figures in Measurements Leftmost zeros appearing in front of nonzero digits are not significant. They act as placeholders.By writing the measurements in scientific notation, you can eliminate such place holding zeros.meter = 7.1 x 10-3 meter, 2 significant figures0.42 meter = 4.2 x 10-1 meter, 2 significant figuresmeter = 9.9 x 10-5 meter, 2 significant figures
21 Determining Significant Figures in Measurements Zeros at the end of a number and to the right of a decimal point are always significant.43.00 meters, 4 significant figures1.010 meters, 4 significant figures9.000 meters, 4 significant figures
22 Determining Significant Figures in Measurements Zeros at the rightmost end of a measurement that lie to the left of an understood decimal point are not significant if they serve as place holders to show the magnitude of the number.300 meters, one significant figure7000 meters, one significant figure27,120 meters, four significant figures
23 Determining Significant Figures in Measurements If such zeros were known measured values, however, then they would be significant. Writing the value in scientific notation makes it clear that these zeros are significant.300 meters = 3.00 x 102 meters, three significant figures.
24 Determining Significant Figures in Measurements There are two situations in which numbers have an unlimited number of significant figures.A number that is counted is exact23 students in the classExactly defined quantities such as those found within a system of measurement60 minutes = 1 hour100 centimeters = 1 meter
25 Significant Figures Addition and Subtraction The answer should be rounded to the same number of decimal places as the measurement with the least number of decimal places.Multiplication and DivisionThe answer should be rounded to the same number of significant figures as the measurement with the least number of significant figures.
26 SummaryIn scientific notation, the coefficient is always a number greater than or equal to one and less than ten. The exponent is an integer.To evaluate accuracy, 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.
27 SummaryMeasurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation.