1 / 20

Chapter 2

Chapter 2. Data Analysis. Units of Measurement. Measurement Comparison to a standard Standard Well defined Make consistent measurements Useful measurement Number Unit SI Units Système Internationale d’Unités —SI Standard unit of measure. Units of Measurement. Base units

allie
Download Presentation

Chapter 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 2 Data Analysis

  2. Units of Measurement • Measurement • Comparison to a standard • Standard • Well defined • Make consistent measurements • Useful measurement • Number • Unit • SI Units • SystèmeInternationaled’Unités—SI • Standard unit of measure

  3. Units of Measurement • Base units • 7 base units (p. 26 Table 2-1) • Defined unit • Based on object or event in physical world • Independent of other units • Time • Frequency of microwave radiation given off by cesium-133 atom • Second, s • Length • Distance light travels through a vacuum in 1/299792458 of a second. • Meter, m • Mass • Defined by the platinum-iridium metal cylinder • Kilogram, kg • Volume • Measure of the amount of a liquid • Liter, L

  4. Units of Measurement • Prefixes • Table p. 26 • mega- micro • hecto (h_): 102 • deka (da_ or dk_): 10 • decimeter • 1 dm = .1 m • 10 cm = 1 dm • 1000 cm3 = 1 dm3 • King Henry Died By Drinking Chocolate Milk • Yotta (Y_): 1024 • 1 septillion • Yocto (y_): 10-24 • 1 septillionth

  5. Units of Measurement • Derived Units • Require a combination of base units • Volume • L X W X H • 1 cm3 = 1 mL = 1 cc • Density • mass/volume • DH2O = 1.00 g/mL • D = m/v • M = DV • V = M/D • Practice p. 29 #1-3; p. 30 #4-11; p. 50 #51-57

  6. Units of Measurement • Temperature • Measure of how hot or cold an object is relative to other objects • kelvin, K • Water • freezes about 273 K • boils about 373 K

  7. Scientific Notation and Dimensional Analysis • Scientific notation expresses numbers as: • M x 10n • M is a number between 1 & 10 • Ten raised to a power (exponent) • n is an integer • Adding & subtracting • Exponents must be the same • Multiplying & dividing • Multiply or divide first factors • Add exponents for multiplication • Subtract exponents for division • Practice Problems p. 32 #12-16; p. 50 #75-78

  8. Scientific Notation and Dimensional Analysis • Dimensional analysis • Solving problems with conversion factors • Conversion factor • Ration based on an equality • Ex. 12 in./1 ft. or 1 ft./12 in. • Ex. 7 days/1 wk • Focuses on units used 48 km =? m (48 km)X (1000 m/1km) = 48,000 m

  9. Scientific Notation and Dimensional Analysis What is a speed of 550 m/s in km/min? • Practice Problems p. 35 #19-28; p. 51 #79-80

  10. How Reliable are Measurements? Accuracy and Precision • Accuracy • The nearness of a measurement to its accepted value • Precision • The agreement between numerical values of two or more measurements that have been made in the same way. • You can be precise without being accurate. • Systematic errors can cause results to be precise but not accurate

  11. How Reliable are Measurements? Accuracy and Precision • Percent error • Compares the size of an error to the size of the accepted value • Calculating Percent Error (Relative Error) • Percent error = error X 100 Value Accepted • Error = Value Accepted – Value Experimental • Take the absolute difference • Ignore if positive or negative integer

  12. How Reliable are Measurements? • Error in Measurement • Some error or uncertainty exists in all measurement • No measurement is known to an infinite number of decimal places. • All measurements should include every digit known with certainty plus the first digit that is uncertain • Practice Problems p. 38 #29-30; p. 51 #81-82

  13. How Reliable are Measurements? • Significant Figures • Represent measurements • Include digits that are known • One digit is estimated

  14. How Reliable are Measurements? Significant Figures

  15. How Reliable are Measurements? • Rounding off numbers

  16. How Reliable are Measurements? • Rounding off numbers • Addition and subtraction • Answer must have same number of digits to right of the decimal place as value with fewest digits to the right of the decimal point. • Example: 1.24 mL 12.4 mL + 124 mL 137.64 mL = 138 mL

  17. How Reliable are Measurements? • Rounding off numbers • Multiplication and division • Answer must have same number of significant figures as the measurement with the fewest significant figures • Practice problems: p. 39 #31-32; p. 41 #33-36; p. 42 #37-44; p. 51 #83-85

  18. Representing Data • Graphing • Circle graphs • Also called pie chart • Show parts of a fixed whole, usually percents • Bar graph • Show how a quantity varies with factors • Ex. Time, location, temperature • Measured quantity on y-axis (vertical axis) • Independent variable on x-axis (horizontal axis) • Heights show how quantity varies

  19. Representing Data • Line Graphs • Points represent intersection of data for two variables • Independent variable on x-axis • Dependent variable on y-axis • Best fit line • Equal points above and below line • Straight line—variables directly related • Rises to the right—positive slope • Sinks to the right—negative slope • Slope = y2-y1 = Δy x2-x1 Δx

  20. Representing Data • Interpreting Graphs • Identify independent and dependent variables • Look at ranges of data • Consider what measurements were taken • Decide if relationship is linear or nonlinear • Practice problems p. 51-52 #86-87

More Related