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Scientific Notation Review

Chapter 2.1 & 2.4 Measurements & Math Review. Scientific Notation Review. 4.326 x 10 8 3.00 x 10 -3 7 x 10 4 N umbers are represented as a multiple of ___ Only _____________________ can be placed in front of the decimal, the rest following

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Scientific Notation Review

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  1. Chapter 2.1 & 2.4 Measurements & Math Review Scientific Notation Review 4.326 x 108 3.00 x 10-3 7 x 104 • Numbers are represented as a multiple of ___ • Only _____________________ can be placed in front of the decimal, the rest following • Exponent is positive = value ______________ • Move decimal to the _________________ • Exponent is negative = value _____________ • Move decimal to the __________________

  2. Practice Convert to scientific notation: 8270 0.0000078 4.0 56 193,000 0.0036520 Convert to decimal form: 6.07 x 10-2 5.19 x 104 2.33 x 101 4.80 x 10-5 8.42 x 10-3 3.57 x 105

  3. Scientific Notation on Your Calculator • The “____” button is a shortcut for scientific notation. • To type 5.46 x 10-8 : • ______________________ • ______________________ • ______________________ • _____________(exponent) • Should display as _______________________

  4. Practice – Scientific Notation on Your Calculator How would your calculator display the following numbers in “EE” notation? • 8001 • 0.000362 Write the following in standard scientific notation. • 5.62E3 • 1.005E-2

  5. Types of Observations • Qualitative - ____________________________ • Examples: _________________________________ __________________________________________ • “______________________________________” • Quantitative - measurements which have both a ______________________________________ • Examples: __________________, 6.63 x 10-3 Joules • “______________________________________________________________________________”

  6. Relationships between variables • Direct relationship: • __________________________________________ • They are said to be __________________________________________ • Inverse relationship: • __________________________________________ • They are said to be __________________________________________

  7. Standard International System of Units (SI Units) * Not fundamental SI Units (these are derived from other measurements)

  8. Measuring Mass • Using an “electronic balance” • Turn • Press • Place Measuring Volume • The volume of a cube is given by its • Thus, the SI Unit of volume is the meter (m), • 1 cubic meter (1m3) = volume of a cube that is 1m on each edge • Smaller units such as _______(also written _______ ) are commonly used in chemistry

  9. Another unit of volume commonly used is the liter (L)

  10. Common devices used in laboratory for measuring liquid volumes

  11. Uncertainty in Measurement • A measurement always has some degree of __________________________________________________________________________________________ • Consider the following example: Do the grapefruits have the same mass?

  12. In recording measurements, the numbers should be written in a way that reflects the _______________ of the ____________________________________. This is done by recording ________ of the certain digits and the ______________________________ (or ____________________________ ) digit. These numbers are called______________________ _____________________________ The uncertainty in the last digit is usually estimated to be _________________ (unless otherwise indicated) Example: The measurement 1.86 grams actually means ____________________________________________ Uncertainty in Measurement (continued)

  13. What is the uncertainty in each of the following measurements? Uncertainty = Uncertainty = Uncertainty = Uncertainty =

  14. Use each ruler to determine the length of the gray rod and the uncertainty in each measurement ________ Precise! ________ Precise! Length = __________ Uncertainty = _________ Length = __________ Uncertainty = _________ _______________________________________________________________________________

  15. Measuring Volume of Liquids in Lab • Liquids adhere to the sides of a glass container forming a _____________________________ (curved surface) • Accurate reading of volume requires that the ___________ of the meniscus is read at ____________________________

  16. Determine the volume of each liquid and the uncertainty in each measurement Volume = _____________ mL Uncertainty = _____________ Volume = _____________ mL Uncertainty = _____________

  17. Why DoesUncertainty Matter? Suppose a doctor leaves orders in a baby’s chart for a nurse to dispense 2 cc of morphine every 4 hours. • Interpreted as a standard scientific measurement, she assumes the uncertainty is __________________. • Thus a dose between ______________ is acceptable. • For a small baby, this range might mean life or death. Better instructions would be to administer 2.00 cc meaning the uncertainty is ____________. • The acceptable dosage range is __________________ cc.

  18. Rules for Counting Significant Figures Non-Zero Digits - _______________________ • 58 has _______ significant figures (SFs) Leading Zero - _________________________ • 0.0936 has _______ significant figures Captive (Smooshed) Zero - _______________ • 208 has _______ significant figures Trailing Zero with Decimal Point - _______________ • 20.670 has _____ significant figures (SFs) Trailing Zero w/o Decimal Point - ________________ • 2900 has _____ significant figures Exact / Counted Numbers - ____________________ • There are students in the class. - ___________

  19. Sig Figs Practice How many sig figs are in each of the following? 408 = 40800 = 408.00 = 967352 = 0.00467 = 0.004670 = 4.26 x 103 = 4.00 x 103 = 4.0030x 103 =

  20. Rounding to A Certain Number of Significant Figures • Rounding is often necessary to avoid expressing a value to a greater degree of _____________ than is consistent with your ____________________________________. • Remember: the ______________________ digit, reading from left to right in a number, is the first significant figure. • Count the required number of sig figs from left to right. • Look _________ digit beyond the required sig figs: • If it is less than 5, ________________ the remaining digits • If it is 5 or greater, _____________________________ the _____________________________and drop the remaining • *If necessary, add __________ as placeholders (Be careful!) • *If necessary, convert to _____________________________ to make __________________________________________

  21. Some Examples of Rounding: • Round 6502 to 1 sig fig: • Round 6502 to 3 sig figs: • Round 6502 to 2 sig figs: • Round 6502 to 5 sig figs:

  22. Rounding Practice Round 40920.60802 to each of the number of significant figures below. 1 sig fig = 2 sig figs = 3 sig figs = 5 sig figs = 7 sig figs = 9 sig figs =

  23. Significant Figures in Multiplication or Division Calculations • The number of sig figs in the result is the ____________ _______________________________________________________________________________________________________________________________________ • Example:

  24. Significant Figures in Addition or Subtraction Calculations • The result has the _______________________________ ____________________________________________________________________________________________ • Easiest to see when numbers are __________ _____________ • Example:

  25. Significant Figures in Mixed Calculations • Simplify each step to determine correct number of sig figs in final answer. Only round at the ______! • Example:

  26. Rounding Rules • In a series of calculations,_________________ ____________________________________________________________________________ • Determine the appropriate number of sig figs and __________________________________. • Convert to _________________________________ if necessary (to make trailing zeroes significant)

  27. Practice – Perform the following calculations. Express answer in correct sig figs. 7.939 + 6.26 + 11.1 = (27.2 × 15.63) ÷ 1.846 = 137.4 × 5.2 + 121 × 1.77 = Must convert to ____________ ____________to make the ___ significant

  28. Precision and Accuracy in Measurements Precision – ____________________________________ ______________________________________________ - Check by _________________________________ Accuracy – ____________________________________ ______________________________________________ - Check by using a ___________________________ to measure

  29. Percent Error Percentage error is a way for scientists to express ______________________________________________________________________________________ The formula is: Example: Determine the percentage error if the value obtained in lab was 1.24 g while the accepted value is 1.30 g.

  30. Metric Prefixes used to modify units(You must memorize these!) Pneumonic Device:

  31. Metrix Units / Prefixes Review Rank the following from smallest to largest: • milliliter, megaliter, microliter, liter • centimeter, decimeter, dekameter, hectameter What unit would you use to measure the following? • The distance from Marymount to your house? _______ • The length of this room? _______ • The mass of a bag of oranges? _______ • The mass of an ant? ______

  32. Metric Conversion Problems: • How many millimeters are in 3.2 Mm? • Convert 175 micrometers to hm.

  33. Density • Density is defined as the __________________ ______________________________________ • Density = __________________________________ • Units: ______________ or _____________ • The density of a substance is inherent to that substance, but ____________________ slightly with a temperature increase, and vice versa • Density of water at 15°C = _____________________ • Density of water at 25°C (ice) = _________________

  34. Density of Selected Substances at 25°C Would a block of wood float or sink in air? Would a block of wood float or sink in ethanol? Which material in the table has the most particles packed together in the smallest volume?

  35. Note: ALWAYS express the answer in the correct number of significant figures!! Density Sample Problems: Calculate the density of mercury if 1.000 x 102 g occupies a volume of 7.36 cm3. Calculate the volume of 65.0 g of the liquid methanol if its density is 0.791 g/mL.

  36. Water Displacement Density Lab • Measure ______ of object • Determine _____________ by water displacement  • Divide ________ by ___________ to determine density file:///Users/lsthilaire/Downloads/water_displacement.swf ORhttp://www.middleschoolchemistry.com/multimedia/chapter3/lesson2#water_displacement

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