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PRINCIPLES OF CHEMISTRY I CHEM 1211 CHAPTER 1

PRINCIPLES OF CHEMISTRY I CHEM 1211 CHAPTER 1. DR. AUGUSTINE OFORI AGYEMAN Assistant professor of chemistry Department of natural sciences Clayton state university. CHAPTER 1 MEASUREMENT. MEASUREMENT. - Is the determination of the dimensions, capacity, quantity, or extent of something

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PRINCIPLES OF CHEMISTRY I CHEM 1211 CHAPTER 1

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  1. PRINCIPLES OF CHEMISTRY I CHEM 1211CHAPTER 1 DR. AUGUSTINE OFORI AGYEMAN Assistant professor of chemistry Department of natural sciences Clayton state university

  2. CHAPTER 1MEASUREMENT

  3. MEASUREMENT - Is the determination of the dimensions, capacity, quantity, or extent of something - Is a quantitative observation and consists of two parts: a number and a scale (called a unit) - Is the tool chemists use most Examples mass, volume, temperature, pressure, length, height, time

  4. SIGNIFICANT FIGURES Precision - Provides information on how closely individual (repeated) measurements agree with one another Accuracy - Refers to how closely individual measurements agree with the true value (correct value) Precise measurements may NOT be accurate

  5. SIGNIFICANT FIGURES Exact Numbers - Values with no uncertainties - There are no uncertainties when counting objects or people (24 students, 4 chairs, 10 pencils) - There are no uncertainties in simple fractions (1/4, 1/7, 4/7, 4/5) Inexact Numbers - Associated with uncertainties - Measurement has uncertainties (errors) associated with it - It is impossible to make exact measurements

  6. SIGNIFICANT FIGURES Measurements contain 2 types of information - Magnitude of the measurement - Uncertainty of the measurement Only one uncertain or estimated digit should be reported Significant Figures digits known with certainty + one uncertain digit

  7. RULES FOR SIGNIFICANT FIGURES 1. Nonzero integers are always significant 4732(4 sig. figs.) 875 (3 sig. figs.) 2. Leading zeros are not significant 0.0045 (2 sig. figs.) 0.00007895 (4 sig. figs.) The zeros simply indicate the position of the decimal point 3. Captive zeros (between nonzero digits) are always significant 1.0025 (5 sig figs.) 12000587 (8 sig figs)

  8. RULES FOR SIGNIFICANT FIGURES 4. Trailing zeros (at the right end of a number) are significant only if the number contains a decimal point 2.3400 (5 sig figs) 23400 (3 sig figs) 5. Exact numbers (not obtained from measurements) are assumed to have infinite number of significant figures

  9. RULES FOR SIGNIFICANT FIGURES How many significant figures are present in each of the following? What is the uncertainty in each case? significant figures uncertainty 1.24 g 3 ± 0.01 g 0.0024 L 2 ± 0.0001 L 0.39200 mL 5 ± 0.00001 mL 3.0026 kg 5 ± 0.0001 kg

  10. RULES FOR SIGNIFICANT FIGURES Rounding off Numbers 1. In a series of calculations, carry the extra digits through to the final result before rounding off to the required significant figures 2. If the first digit to be removed is less than 5, the preceding digit remains the same (round down) Round to two significant figures 2.53 rounds to 2.5 and 1.24 rounds to 1.2

  11. RULES FOR SIGNIFICANT FIGURES Rounding off Numbers 3. If the first digit to be removed is greater than 5, the preceding digit increases by 1 (round up) (2.56 rounds to 2.6 and 1.27 rounds to 1.3) 4. If the digit to be removed is exactly 5 (round even) - The preceding number is increased by 1 if that results in an even number (2.55 rounds to 2.6 and 1.35000 rounds to 1.4) - The preceding number remains the same if that results in an odd number (2.45 rounds to 2.4 and 1.25000 rounds to 1.2)

  12. RULES FOR SIGNIFICANT FIGURES - The certainty of the calculated quantity is limited by the least certain measurement, which determines the final number of significant figures Multiplication and Division - The result contains the same number of significant figures as the measurement with the least number of significant figures 2.0456 x 4.02 = 8.223312 = 8.22 3.20014 ÷ 1.2 = 2.6667833 = 2.7

  13. RULES FOR SIGNIFICANT FIGURES - The certainty of the calculated quantity is limited by the least certain measurement, which determines the final number of significant figures Addition and Subtraction - The result contains the same number of decimal places as the measurement with the least number of decimal places = 4.03 = 6.00 (not 6) = 5.5

  14. SCIENTIFIC NOTATION - Used to express too large or too small numbers (with many zeros) in compact form - The product of a decimal number between 1 and 10 (the coefficient) and 10 raised to a power (exponential term) 24,000,000,000,000 = 2.4 x1013 exponent (power) coefficient exponential term 0.000000458 = 4.58 x10-7

  15. SCIENTIFIC NOTATION - Provides a convenient way of writing the required number of significant figures 6300000 to 4 significant figures= 6.300 x 106 2400 to 3 significant figures = 2.40 x 103 0.0003 to 2 significant figures = 3.0 x 10-4

  16. SCIENTIFIC NOTATION - Add exponents when multiplying exponential terms (5.4 x 104) x (1.23 x 102) = (5.4 x 1.23) x 10 4+2 = 6.6 x 106 - Subtract exponents when dividing exponential terms (5.4 x 104)/(1.23 x 102) = (5.4/1.23) x 10 4-2 = 4.4 x 102

  17. MEASUREMENT SYSTEMS Two measurement systems: English System of Units (commercial measurements): pound, quart, inch, foot, gallon Metric System of Units (scientific measurements) SI units (Systeme International d’Unites) liter, meter, gram More convenient to use

  18. FUNDAMENTAL (BASE) UNITS Physical Quantity Mass Length Time Temperature Amount of substance Electric current Luminous intensity Name of Unit Kilogram Meter Second Kelvin Mole Ampere Candela Abbreviation kg m s(sec) K mol A cd

  19. DERIVED UNITS Area = length x length = m x m = m2 Volume = m x m x m = m3 Volume may also be expressed in LITERS (L) 1L = 1000 mL = 1000 cm3 or cubic centimeters (c.c.) Implies 1mL = 1c.c. mL is usually used for volumes of liquids and gases c.c. is usually used for volumes of solids Density = kg/ m3

  20. DERIVED UNITS Physical Quantity Force Pressure Energy Power Frequency Name of Unit Newton Pascal Joule Watt Hertz Abbreviation N (m-kg/s2) Pa (N/m2; kg/(m-s2) J (N-m; m2-kg/s2) W (J/s; m2-kg/s3) Hz (1/s)

  21. UNIT CONVERSIONS Prefix Giga Mega Kilo Deci Centi Milli Micro Nano Pico Femto Abbreviation G M k d c m µ n p f Notation 109 106 103 10-1 10-2 10-3 10-6 10-9 10-12 10-15

  22. UNIT CONVERSIONS 1 gigameter (Gm) 1 megameter (Mm) 1 kilometer (km) 1 decimeter (dm) 1 centimeter (cm) 1 millimeter (mm) 1 micrometer (µm) 1 nanometer (nm) 1 picometer (pm) 1 femtometer (fm) = 109 meters = 106 meters = 103 meters = 10-1 meter = 10-2 meter = 10-3 meter = 10-6 meter = 10-9 meter = 10-12 meter = 10-15 meter

  23. UNIT CONVERSIONS Length/Distance 2.54 cm = 1.00 in. 12 in. = 1 ft 1 yd = 3 ft 1 m = 39.4 in. 1 m = 1.09 yd 1 km = 0.621 mile 1 km = 1000 m Time 1 min = 60 sec 1 hour = 60 min 24 hours = 1 day 7 days = 1 week Volume 1 gal = 4 qt 1 qt = 0.946 L 1 L = 1.06 qt 1 L = 0.265 gal 1 mL = 0.034 fl. oz. Mass 1 Ib = 454 g 1 Ib = 16 oz 1 kg = 2.20 lb 1 oz = 28.3 g

  24. UNIT CONVERSIONS Conversion Factors 1 km = 1000 m » or 1 L = 1000 mL » or or 24 hours = 1 day » 1 kg = 2.20 lb » or

  25. UNIT CONVERSIONS given number · unit new unit = new number · new unit unit to be converted quantity to be expressed in new units quantity now expressed in new units conversion factor given data desired unit = answer in desired unit unit of given data

  26. UNIT CONVERSIONS Convert 34.5 mg to g How many gallons of juice are there in 20.0 liters of the juice? Convert 4.0 gallons to quarts

  27. UNIT CONVERSIONS Convert 2.64 μg to kg Convert 3.912 m2 to km2 Convert 4.0 cm3 to μm3

  28. DENSITY - The amount of mass in a unit volume of a substance Density= Ratio of mass to volume = Units Solids: grams per cubic centimeter (g/cm3) Liquids: grams per milliliter (g/mL) Gases: grams per liter (g/L) - Density of 2.3 g/mL implies 2.3 grams per 1 mL - Density usually changes with change in temperature

  29. DENSITY For a given liquid: - Objects with density less than that of the liquid will float - Objects with density greater than that of the liquid will sink - Objects with density equal to that of the liquid will remain stationary (neither float nor sink)

  30. DENSITY The liquid level in a graduated cylinder reads 12.20 mL. The level rises to 18.90 mL when 129.31 g of piece of gold is added to the cylinder. What is the density of gold? Volume of the piece of gold = 18.90 mL – 12.20 mL = 6.70 mL Mass of the piece of gold = 129.31 g Density = mass/volume = 129.31 g/6.70 mL = 19.3 g/mL or 19.3 g/cm3

  31. TEMPERATURE - The degree of hotness or coldness of a body or environment 3 common temperature scales Metric system: Celsius and Kelvin English system: Fahrenheit Celsius Scale (oC): Reference points are the boiling and freezing points of water (0oC and 100oC) - 100 degree interval Kelvin Scale (K): Is the SI unit of temperature (no degree sign) The lowest attainable temperature on the Kelvin scale is 0 (-273 oC) referred to as the absolute zero

  32. TEMPERATURE Fahrenheit Scale: Water freezes at 32oF and boils at 212oF - 180 degree interval or or 10o, 40o, 60o may be considered as 2 significant figures 100o may be considered as 3 significant figures

  33. TEMPERATURE Convert 29 oC to K Convert 29 K to oC Convert 29 oF to oC Convert 29 oC to oF

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