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Scientific Measurements and Conversions August 8

Learn how to make accurate measurements, convert units, and understand the principles of scientific measurements in this comprehensive guide. Practice sample problems and improve your skills in dimensional analysis.

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Scientific Measurements and Conversions August 8

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  1. Scientific Measurements and ConversionsAugust 8 Take out your notebook, label appropriately, copy and solve: Warm-up: How many minutes are in 6.2 hours? How many dollars does 35 quarters equal?

  2. Introduction to Chemistry • SCSh4. Students will use tools and instruments for observing, measuring, and manipulating scientific equipment and materials. • a. Develop and use systematic procedures for recording and organizing information. • b. Use technology to produce tables and graphs. • c. Use technology to develop, test, and revise experimental or mathematical models.

  3. Measurements

  4. With the person next to you, identify one object in the room that has a measurement quantity. • Be prepared to discuss the: • unit of measurement • description of the measurement • What other qualities does the object have?

  5. Measurements • Review

  6. Measurements • Derived SI Units • Combinations of SI base units form derived units • Example: pressure is measured in kg/m•s2, or pascals

  7. Measurements • Derived SI Units • Volume is the amount of space occupied by an object • The derived SI unit is cubic meters, m3 • The cubic centimeter, cm3, is often used • 1 mL = 1 cm3

  8. Measurements • Derived SI Units • Density is the ratio of mass to volume, or mass divided by volume • The derived SI unit is kilograms per cubic meter, kg/m3 • g/cm3 or g/mL are also used • Density is a characteristic physical property of a substance

  9. Measurements • Derived SI Units • Sample Problem • A sample of aluminum metal has a mass of 8.4 g. The volume of the sample is 3.1 cm3. Calculate the density of aluminum

  10. Measurements • Derived SI Units • Sample Problem Answer • Given:mass (m) = 8.4 g volume (V) = 3.1 cm3 • Unknown:density (D) • Solution:

  11. Measurements • Dimensional analysis is a mathematical technique that allows you to use units to solve problems involving measurements • Quantity sought = quantity given × conversion factor • Example:the number of quarters in 12 dollars number of quarters = 12 dollars × conversion factor

  12. Measurements • Conversion Factors • Sample Problem • Express a mass of 5.712 grams in milligrams and in kilograms

  13. Measurements • Conversion Factors • Sample Problem Answer • Given: 5.712 g • Unknown: mass in mg and kg • Solution: mg 1 g = 1000 mg Possible conversion factors:

  14. Measurements • Conversion Factors • Sample Problem Answer • Given: 5.712 g • Unknown: mass in mg and kg • Solution:kg 1 000 g = 1 kg Possible conversion factors:

  15. Mustang ChallengeSEHS is recruiting a live mascot, but wants the biggest and strongest. Complete calculation on notes page from yesterday. Mustang #1: 307.82 mg #2 : 00.0756 kg #3 : 48.004 x 10 g Which mustang weighs the most? -2

  16. Scientific Measurements

  17. Measurements • Accuracy and Precision • Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured • Precision refers to the closeness of a set of measurements of the same quantity made in the same way

  18. Scientific MeasurementsAugust 8 Take out your homework sheet and notes from yesterday. Copy and Solve: A flower grows 2.05 cm for each 50 mL of water given. How tall will the plant grow is given 10,000 mL of water?

  19. Scientific MeasurementsAugust 8 Take out your notebook, label appropriately, copy and solve: Warm-up: How many mL are in one Liter? A flower requires 25 mL to grow 8 inches. If you feed the flower 158 mL, how tall will the flower grow?

  20. Scientific MeasurementsAugust 9 Take out your notebook, label appropriately, copy and solve: Warm-up: How many hectoliters are in one kiloliter? A flower grows 2.05 cm for each 50 mL of water given. How tall will the plant grow is given 10,000 mL of water?

  21. DENSITY LAB- Rm. 304 You will need: One sheet of paper Pencil Calculator Observe all lab safety rules Read and follow all directions Goggles

  22. Scientific MeasurementsAugust 10 Pass your lab to the center, make sure your name is on it Take out your notebook, label appropriately, copy and solve: Warm-up: How many milliliters of water will it take to fill a 2 L bottle that already contains 1.87 L of water?

  23. Measurements Accuracy and Precision

  24. Measurements • Significant Figures • Significant figures in a measurement consist of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated • The term significant does not mean certain

  25. Measurements • Significant Figures • Reporting measurements using significant figures

  26. Measurements • Significant Figures • Determining the number of significant figures

  27. Measurements • Significant Figures • Sample Problem • How many significant figures are in each of the following measurements? a. 28.6 g b. 3440. cm c. 910 m d. 0.04604 L e. 0.0067000 kg

  28. Measurements • Significant Figures • Sample Problem Solution a. 28.6 g There are no zeros, so all three digits are significant b. 3440. cm By rule 4, the zero is significant because it is immediately followed by a decimal point; there are 4 significant figures c. 910 m By rule 4, the zero is not significant; there are 2 significant figures

  29. Measurements • Significant Figures • Sample Problem Solution d. 0.04604 L By rule 2, the first two zeros are not significant; by rule 1, the third zero is significant; there are 4 significant figures e. 0.006 700 0 kg By rule 2, the first three zeros are not significant; by rule 3, the last three zeros are significant; there are 5 significant figures

  30. Measurements • Significant Figures • Addition or subtraction with significant figures • When adding or subtracting decimals, the answer must have the same number of digits to the right of the decimal point as there are in the measurement having the fewest digits to the right of the decimal point

  31. Measurements • Significant Figures • Multiplication or division with significant figures • For multiplication or division, the answer can have no more significant figures than are in the measurement with the fewest number of significant figures

  32. Measurements • Significant Figures • Sample Problems • Express each answer to the correct number of significant figures a. 5.44 m - 2.6103 m b. 2.4 g/mL 15.82 mL

  33. Measurements • Significant Figures • Sample Problem Solutions a. 5.44 m - 2.6103 m = 2.84 m There should be two digits to the right of the decimal point, to match 5.44 m b. 2.4 g/mL 15.82 mL = 38 g There should be two significant figures in the answer, to match 2.4 g/mL

  34. Measurements • Scientific Notation • In scientific notation, numbers are written in the form M × 10n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number • Example: 0.000 12 mm = 1.2 × 10−4 mm • Move the decimal point four places to the right and multiply the number by 10−4

  35. Measurements • Scientific Notation • Determine M by moving the decimal point in the original number to the left or the right so that only one nonzero digit remains to the left of the decimal point • Determine n by counting the number of places that you moved the decimal point. If you moved it to the left, n is positive. If you moved it to the right, n is negative

  36. Measurements or • Scientific Notation • Addition and subtraction —These operations can be performed only if the values have the same exponent (n factor) • Example: 4.2 × 104 kg + 7.9 × 103 kg

  37. Measurements = (5.23 × 7.1)(106 +10-2) = 37.133 × 104 µm2 = 3.7  105 µm2 • Scientific Notation • Multiplication —The M factors are multiplied, and the exponents are added algebraically • Example: (5.23 × 106 µm)(7.1 × 10−2 µm)

  38. Measurements = (5.44 / 8.1)(107 -104) = 0.6716049383 × 103 = 6.7  102 g/mol • Scientific Notation • Division — The M factors are divided, and the exponent of the denominator is subtracted from that of the numerator • Example:

  39. Express the following quantities in scientific notation: • a.8 800 000 000 m • 0.0015 kg • 0.000 000 000 06 kg/m3 • 8 002 000 Hz • 0.009 003 amp • 70 000 000000000000 km • 6028 L • 0.2105 g • 600 005 000 kJ/h • j. 33.8 m2

  40. Matter/ MixturesAugust 13 Take out your notebook, label appropriately, copy #2 and solve: Warm-up: 1. A metallurgist is going to make an experimental alloy that requires adding 325 g of bismuth to 2.500 kg of molten lead. What is the total mass of the mixture in kilograms? 2. 2.58 x 10 cm x 3.3 x 10 cm = 2 3

  41. Matter

  42. Matter and Its Properties • Matter • Volume isthe amount of three dimensional space an object occupies • Mass isa measure of the amount of matter • Matter isanything that has mass and takes up space

  43. Matter and Its Properties • Properties of Matter • Extensive propertiesdepend on the amount of matter that is present • Volume • Mass • The amount of energy in a substance

  44. Matter and Its Properties • Properties of Matter • Intensive propertiesdo not depend on the amount of matter present • Melting point • Boiling point • Density • Ability to conduct electricity • Ability to transfer energy as heat

  45. Matter and Its Properties • Physical Properties/Physical Changes • Physical property is a characteristic that can be observed or measured without changing the identity of the substance • Color, volume, hardness, temperature • Melting point and boiling point • Physical change is a change in a substance that does not involve a change in the identity of the substance • Grinding, cutting, melting, and boiling

  46. Matter and Its Properties • Physical Properties/Physical Changes • Change of state is a physical change of a substance from one state to another • Solid state, matter has definite volume and definite shape • Liquid state, matter has a definite volume but an indefinite shape • Gas state, matter has neither definite volume nor definite shape • Plasma is a high-temperature physical state of matter in which atoms lose most of their electrons, particles that make up atoms

  47. Physical and Chemical Properties Examples of Physical Properties Boiling point Color Slipperiness Electrical conductivity Melting point Taste Odor Dissolves in water Shininess (luster) Softness Ductility Viscosity (resistance to flow) Volatility Hardness Malleability Density (mass / volume ratio) Examples of Chemical Properties Burns in air Reacts with certain acids Decomposes when heated Explodes Reacts with certain metals Reacts with certain nonmetals Tarnishes Reacts with water Is toxic Chemical properties can ONLY be observed during a chemical reaction! Ralph A. Burns, Fundamentals of Chemistry 1999, page 23

  48. Pyrex Physical & Chemical Changes CO2 crushing heating PHYSICAL CHANGE CHEMICAL CHANGE CaO Limestone, CaCO3 Crushed limestone, CaCO3 Lime and carbon dioxide, CaO + CO2

  49. Pyrex Pyrex Sunlight energy O2 H2O2 H2O Light hastens the decomposition of hydrogen peroxide, H2O2. The dark bottle in which hydrogen peroxide is usually stored keeps out the light, thus protecting the H2O2 from decomposition.

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