UNIT 1-2 MEASUREMENT,SIGNIFICANT FIGURES AND CONVERSION FACTOR

1. UNIT 1-2 MEASUREMENT,SIGNIFICANT FIGURES AND CONVERSION FACTOR

2. Soot (carbon) depositing on metal • The process of soot producing • The process of depositing on metal

3. Classify each of the following as an observation, a law or a theory • A. Chlorine is a highly reactive gas. • B. If elements are listed in order of increasing mass of their atoms, their chemical reactivity follows a repeating pattern. • C. The reactivity of elements depends on the arrangement of their electrons. • Law • Law • theory

4. A measurement is a quantitative observation consisting of 2 parts: Part 1 - number Part 2 - scale (unit) Examples: 20grams 6.63 x 10-34Joule·seconds Nature of Measurement

5. The Fundamental SI Units

6. CELSIUS & KELVIN • TK = TC + 273.15

7. Derived SI Units-Volume&density • Volume=(length)3 • SI unit of volume: m3 • 1 L=1 dm3 • 1ml=1 cm3 • Density= m/V

8. SI Prefixes Common to Chemistry

9. Accuracy - how close a measurements is to an accepted or true value. • Precision - the ability to reproduce a measurement. How close are the measurements between each other. Precision and Accuracy Precise but not accurate Precise AND accurate Neither accurate nor precise

10. Types of Error • Random Error(Indeterminate Error) - measurement has an equal probability of being highorlow. • Systematic Error(Determinate Error) - Occurs in the same direction each time (high or low), often resulting from poor technique or incorrect calibration. This can result in measurements that are precise, but not accurate.

11. Uncertainty in Measurement • Some devices are more precise than others. • Any measuring instrument falls within a certain range of precision. • When we measure something, we always estimate between the smallest marks. • A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty. • Measurements are performed with instruments • No instrument can read to an infinite number of decimal places

12. Significant figures • 4.2 cm • 4.3 cm • 4.4 cm • 4.40cm • 4.41cm • 4.39cm • 4.3cm • 4.40cm

13. Identifying Sig Fig • All non-zero digits are significant • Pacific-Atlantic Rule

14. Pacific-Atlantic Rule • 65.01 • Decimal present=Pacific to Atlantic=Counting left to right. First non-zero number and all numbers after that are significant.

15. 1700 • Decimal absent=Atlantic to Pacific= from right to left, counting the first non-zero number and all the number after it.

16. 0.0250 • Decimal present • Pacific to Atlantic • Left to right, from first non-zero number to the end of the reading.

17. Rounding • Rules • Greater than 5 round value up • Less than 5 round value down • If equal to 5, follow naked 5 rule: • Even Stevens, the number remains the same • Odd up, number rounds up • Example: 2.35000, round to 2 sig figs.

18. Sig Fig Calculations • Multiplying/Dividing: Least amount of sig figs • Units do not need to be the same • Example: mi/hr or N*m • When dividing variables with exponents subtract the exponents • Example: 8 m3/ 2 m5 • When multiplying variables with exponents add them • Example: 3 km2 x 7 km4 • Adding/Subtracting: Least amount of decimal places • Units must be like terms • For multi-step calculation, the SF rules must be applied in each step. • The SF rules must be applied in all questions of the AP test.

19. Sig Fig Practice #1 Calculation Calculator says: Answer 22.68 m2 3.24 m x 7.0 m 23 m2 100.0 g ÷ 23.7 cm3 4.22 g/cm3 4.219409283 g/cm3 0.02 cm x 2.371 cm 0.05 cm2 0.04742 cm2 710 m ÷ 3.0 s 236.6666667 m/s 240 m/s 5870 lb·ft 1818.2 lb x 3.23 ft 5872.786 lb·ft 2.9561 g/mL 2.96 g/mL 1.030 g ÷ 2.87 mL

20. Sig Fig Practice #2 Calculation Calculator says: Answer 10.24 m 3.24 m + 7.0 m 10.2 m 100.0 g - 23.73 g 76.3 g 76.27 g 0.02 cm + 2.371 cm 2.39 cm 2.391 cm 713.1 L - 3.872 L 709.228 L 709.2 L 1821.6 lb 1818.2 lb + 3.37 lb 1821.57 lb 0.160 mL 0.16 mL 2.030 mL - 1.870 mL

21. Conversions/Dimensional Analysis • Metric Prefixes • Conversion Factor (key) • Conversion Table • Sample problem: • How many micro-ounces are in 7.76 mg? 7.76 mg x 1 x 10-3g x 1kg x 2.12 lbs x 16 oz x 1microoz = 1 mg x 1 x 103 g x 1 kg x 1 lb x 1 x 10-6oz 263 microoz

22. Example: Dimensional Analysis • The latest model corvette has an engine with a displacement of 6.20 L. What is the displacement in units of cubic inches? 6.20 L x 1 ft3 x (12in)3 = 378 in3 28.32 L (1ft)3

23. The three major temperature scales. TK = TC + 273.15 TC = TK – 273.15

24. Converting Between Celsius & Fahrenheit • More complex because both degree sizes and zero points are different. So two adjustments need to be made: • One for the degree size Since 212*F = 100*C and 32*F = 0*C: 212 – 32 = 180 Fahrenheit degrees = 100 – 0 = 100 Celsius degrees 180*F or 9*F 100*C or 5*C or the reciprocal depending on which way you go. • And one for the zero point Since 32*F = 0*C then we subtract 32 to find Celsius temp and add 32 to find Fahrenheit temp. TC = (TF – 32*F) 5*C/9*F TF = TC x 9*F/5*C + 32

25. 1.19, 1.23(b), 1.29 (c) 1.35, 1.37,1.41(b) and (d), 1.43 Homework