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Matter, Energy, and Measurement

0. Matter, Energy, and Measurement. Chapter 1. The Scientific Approach to Knowledge. philosophers try to understand the universe by reasoning and thinking about “ideal” behavior scientists try to understand the universe through empirical knowledge gained through observation and experiment.

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Matter, Energy, and Measurement

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  1. 0 Matter, Energy, and Measurement Chapter 1

  2. The Scientific Approach to Knowledge • philosophers try to understand the universe by reasoning and thinking about “ideal” behavior • scientists try to understand the universe through empirical knowledge gained through observation and experiment Tro, Chemistry: A Molecular Approach

  3. From Observation to Understanding • Hypothesis – a tentative interpretation or explanation for an observation • falsifiable – confirmed or refuted by other observations • tested by experiments – validated or invalidated • when similar observations are consistently made, it can lead to a Scientific Law • a statement of a behavior that is always observed • summarizes past observations and predicts future ones • Law of Conservation of Mass Tro, Chemistry: A Molecular Approach

  4. From Specific to General Understanding • a hypothesis is a potential explanation for a single or small number of observations • a theory is a general explanation for the manifestation and behavior of all nature • models • pinnacle of scientific knowledge • validated or invalidated by experiment and observation Tro, Chemistry: A Molecular Approach

  5. Classification of Matter States of Matter Physical and Chemical Properties Physical and Chemical Changes

  6. Classification of Matter • matter is anything that has mass and occupies space • we can classify matter based on whether it’s solid, liquid, or gas Tro, Chemistry: A Molecular Approach

  7. Classifying Matterby Physical State • matter can be classified as solid, liquid, or gas based on the characteristics it exhibits • Fixed = keeps shape when placed in a container • Indefinite = takes the shape of the container Tro, Chemistry: A Molecular Approach

  8. Solids • the particles in a solid are packed close together and are fixed in position • though they may vibrate • the close packing of the particles results in solids being incompressible • the inability of the particles to move around results in solids retaining their shape and volume when placed in a new container, and prevents the particles from flowing Tro, Chemistry: A Molecular Approach

  9. Liquids • the particles in a liquid are closely packed, but they have some ability to move around • the close packing results in liquids being incompressible • but the ability of the particles to move allows liquids to take the shape of their container and to flow – however, they don’t have enough freedom to escape and expand to fill the container Tro, Chemistry: A Molecular Approach

  10. Gases • in the gas state, the particles have complete freedom from each other • the particles are constantly flying around, bumping into each other and the container • in the gas state, there is a lot of empty space between the particles • on average Tro, Chemistry: A Molecular Approach

  11. 0 Changes of State • Solid to Liquid = Melting • Liquid to Solid = Freezing • Liquid to Gas = Evaporation • Gas to Liquid = Condensation • Solid to Gas = Sublimation (e.g. dry ice) • Gas to Solid = Deposition

  12. Changes in Matter • changes that alter the state or appearance of the matter without altering the composition are called physical changes • changes that alter the composition of the matter are called chemical changes • during the chemical change, the atoms that are present rearrange into new molecules, but all of the original atoms are still present Tro, Chemistry: A Molecular Approach

  13. Physical Changes – changes in the physical appearance of a substance, still have the same substance after change e.g. • ripping up a piece of paper • Melting an ice cube • Freezing water • Boiling water

  14. Dissolving of Sugar Subliming of Dry Ice C12H22O11(s) CO2(g) Dry Ice CO2(s) C12H22O11(aq) Common Physical Changes • processes that cause changes in the matter that do not change its composition • state changes • boiling / condensing • melting / freezing • subliming • dissolving Tro, Chemistry: A Molecular Approach

  15. Physical Changes in Matter The boiling of water is a physical change. The water molecules are separated from each other, but their structure and composition do not change. Tro, Chemistry: A Molecular Approach

  16. Changes in Matter Chemical Changes – involve a chemical reaction, have different substance after the change than had before. e.g. • water decomposing into oxygen and hydrogen • Gasoline burning in air to produce carbon dioxide and water

  17. Chemical Changes in Matter The rusting of iron is a chemical change. The iron atoms in the nail combine with oxygen atoms from O2 in the air to make a new substance, rust, with a different composition. Tro, Chemistry: A Molecular Approach

  18. C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) Common Chemical Changes • processes that cause changes in the matter that change its composition • rusting • processes that release lots of energy • burning Tro, Chemistry: A Molecular Approach

  19. Properties of Matter • physical properties are the characteristics of matter that can be changed without changing its composition • characteristics that are directly observable • chemical properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy • characteristics that describe the behavior of matter Tro, Chemistry: A Molecular Approach

  20. 0 Properties of Matter • Physical Properties – attributes of a substance, does not involve a chemical reaction • color - density • Temperature - volume • mass • boiling point • melting point

  21. 0 Properties of Matter • Chemical properties – how a substance behaves around other substances, involves a chemical reaction • flammability • Reactivity - corrosion

  22. 0 Measurement In Science

  23. 0 All measurements contain the following • A number • A unit following the number indicating the type of measurement made e.g. 12.0 ft or 100C

  24. How do scientists report numbers? Scientific notation (book calls it exponential notation) • Used to express very large or very small numbers • Based on powers of ten

  25. How wide is our universe? 210,000,000,000,000,000,000,000 miles (22 zeros) This number is written in decimal notation. When numbers get this large, it is easier to write them in scientific notation.

  26. Scientific Notation A number is expressed in scientific notation when it is in the form a x 10n where a is between 1 and 10 and n is an integer

  27. Write the width of the universe in scientific notation. 210,000,000,000,000,000,000,000 miles Where is the decimal point now? After the last zero. Where would you put the decimal to make this number be between 1 and 10? Between the 2 and the 1

  28. 2.10,000,000,000,000,000,000,000. How many decimal places did you move the decimal? 23 When the original number is more than 1, the exponent is positive. The answer in scientific notation is 2.1 x 1023

  29. 1) Express 0.0000000902 in scientific notation. Where would the decimal go to make the number be between 1 and 10? 9.02 The decimal was moved how many places? 8 When the original number is less than 1, the exponent is negative. 9.02 x 10-8

  30. 1) Express 0.0000000902 in scientific notation. Where would the decimal go to make the number be between 1 and 10? 9.02 The decimal was moved how many places? 8 When the original number is less than 1, the exponent is negative. 9.02 x 10-8

  31. Write 28750.9 in scientific notation. • 2.87509 x 10-5 • 2.87509 x 10-4 • 2.87509 x 104 • 2.87509 x 105

  32. 2) Express 1.8 x 10-4 in decimal notation. 0.00018 3) Express 4.58 x 106 in decimal notation. 4,580,000 On the graphing calculator, scientific notation is done with the button. 4.58 x 106 is typed 4.58 6

  33. 4) Use a calculator to evaluate: 4.5 x 10-5 1.6 x 10-2 Type 4.5 -5 1.6 -2 You must include parentheses if you don’t use those buttons!! (4.5 x 10 -5) (1.6 x 10 -2) 0.0028125 Write in scientific notation. 2.8125 x 10-3

  34. 5) Use a calculator to evaluate: 7.2 x 10-9 1.2 x 102On the calculator, the answer is: 6.E -11 The answer in scientific notation is 6 x 10 -11 The answer in decimal notation is 0.00000000006

  35. 6) Use a calculator to evaluate (0.0042)(330,000).On the calculator, the answer is 1386. The answer in decimal notation is 1386 The answer in scientific notation is 1.386 x 103

  36. 7) Use a calculator to evaluate (3,600,000,000)(23).On the calculator, the answer is: 8.28 E +10 The answer in scientific notation is 8.28 x 10 10 The answer in decimal notation is 82,800,000,000

  37. Write (2.8 x 103)(5.1 x 10-7) in scientific notation. • 14.28 x 10-4 • 1.428 x 10-3 • 14.28 x 1010 • 1.428 x 1011

  38. Write in PROPER scientific notation.(Notice the number is not between 1 and 10) 8) 234.6 x 109 2.346 x 1011 9) 0.0642 x 104 on calculator: 642 6.42 x 10 2

  39. Write 531.42 x 105 in scientific notation. • .53142 x 102 • 5.3142 x 103 • 53.142 x 104 • 531.42 x 105 • 53.142 x 106 • 5.3142 x 107 • .53142 x 108

  40. Measurementand Significant Figures

  41. What Is a Measurement? • quantitative observation • comparison to an agreed- upon standard • every measurement has a number and a unit Tro, Chemistry: A Molecular Approach

  42. A Measurement • the unit tells you what standard you are comparing your object to • the number tells you • what multiple of the standard the object measures • the uncertainty in the measurement • scientific measurements are reported so that every digit written is certain, except the last one which is estimated Tro, Chemistry: A Molecular Approach

  43. Estimating the Last Digit • for instruments marked with a scale, you get the last digit by estimating between the marks • if possible • mentally divide the space into 10 equal spaces, then estimate how many spaces over the indicator mark is Tro, Chemistry: A Molecular Approach

  44. Significant Figures Some numbers are exact: There are 60 seconds in 1 minute 25 cents in 1 quarter 12 eggs in one dozen There is no uncertainty in any of these numbers. In other words there are 12.0000000000000000000000000000000000 eggs in 1 dozen (add as many zeros as you like)

  45. Tro, Chemistry: A Molecular Approach

  46. Significant Figures • the non-place-holding digits in a reported measurement are called significant figures • some zeros in a written number are only there to help you locate the decimal point • significant figures tell us the range of values to expect for repeated measurements • the more significant figures there are in a measurement, the smaller the range of values is 12.3 cm has 3 sig. figs. and its range is 12.2 to 12.4 cm 12.30 cm has 4 sig. figs. and its range is 12.29 to 12.31 cm Tro, Chemistry: A Molecular Approach

  47. Counting Significant Figures • All non-zero digits are significant • 1.5 has 2 sig. figs. • Interior zeros are significant • 1.05 has 3 sig. figs. • Leading zeros are NOT significant • 0.001050 has 4 sig. figs. • 1.050 x 10-3 Tro, Chemistry: A Molecular Approach

  48. Counting Significant Figures • Trailing zeros may or may not be significant • Trailing zeros after a decimal point are significant • 1.050 has 4 sig. figs. • Zeros at the end of a number without a written decimal point are ambiguous and should be avoided by using scientific notation • if 150 has 2 sig. figs. then 1.5 x 102 • but if 150 has 3 sig. figs. then 1.50 x 102 Tro, Chemistry: A Molecular Approach

  49. diameter of a circle 2 radius of a circle = Significant Figures and Exact Numbers • Exact numbers have an unlimited number of significant figures • A number whose value is known with complete certainty is exact • from counting individual objects • from definitions • 1 cm is exactly equal to 0.01 m • from integer values in equations • in the equation for the radius of a circle, the 2 is exact Tro, Chemistry: A Molecular Approach

  50. Example 1.5 Determining the Number of Significant Figures in a Number How many significant figures are in each of the following? 0.04450 m 5.0003 km 10 dm = 1 m 1.000 × 105 s 0.00002 mm 10,000 m 4 sig. figs.; the digits 4 and 5, and the trailing 0 5 sig. figs.; the digits 5 and 3, and the interior 0’s infinite number of sig. figs., exact numbers 4 sig. figs.; the digit 1, and the trailing 0’s 1 sig. figs.; the digit 2, not the leading 0’s Ambiguous, generally assume 1 sig. fig. Tro, Chemistry: A Molecular Approach

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