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Chemistry: The Study of Change

Chemistry: The Study of Change. Chapter 1. CHEMISTRY. UNITS. PREFIXES. The number of atoms in 12 g of carbon:. 602,200,000,000,000,000,000,000. The mass of a single carbon atom in grams:. 0.0000000000000000000000199. SCIENTIFIC NOTATION. N is a number between 1 and 10.

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Chemistry: The Study of Change

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  1. Chemistry: The Study of Change Chapter 1

  2. CHEMISTRY

  3. UNITS

  4. PREFIXES

  5. The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000,000 The mass of a single carbon atom in grams: 0.0000000000000000000000199 SCIENTIFIC NOTATION N is a number between 1 and 10 n is a positive or negative integer 6.022 x 1023 1.99 x 10-23

  6. move decimal left move decimal right SCIENTIFIC NOTATION 568.762 0.00000772 n > 0 n < 0 568.762 = __________ 0.00000772 = ___________

  7. SIGNIFICANT FIGURES

  8. Once you start the counting don’t stop!

  9. SIGNIFICANT FIGURES Rule 1: Every nonzero digit in a measurement is significant. Examples: 24.7 0.22 569 Rule 2: Zeros appearing between nonzero digits are significant. Examples: 7003 60.8 0.502 Rule 3 A ZERO is NOT significant when it is a placeholder. A placeholder is used to show the location of the decimal point. Examples: .00099 5280 700

  10. SIG FIGS CONT. Rule 4: Zeros at the end of a number and to the right of a decimal point are always significant. Examples: 86.0 46.00 1.010 Rule 5: When a number is counted or defined within a system of measurement, there is an infinite amount of significant digits. Examples: 11 students 100 cm = 1 m

  11. COUNT THE SIG FIGS: 24 mL 3001 g 0.0320 m3 6.4 x 104 molecules 560 kg

  12. 89.332 + 1.1 one significant figure after decimal point two significant figures after decimal point 90.432 round off to ________ round off to ________ 3.70 -2.9133 0.7867 SIG FIGS – Addition and Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers.

  13. 3 sig figs round to 3 sig figs 2 sig figs round to 2 sig figs SIG FIGS – Multiplication and Division The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x 3.6666 = 16.536366 = _______ 6.8 ÷ 112.04 = 0.0606926 = _______

  14. 1000 mL 1L L2 1.63 L x = 1630 mL mL 1L 1.63 L x = 0.001630 1000 mL FACTOR LABEL METHOD • Determine which unit conversion factor(s) are needed • Carry units through calculation • If all units cancel except for the desired unit(s), then the problem was solved correctly. How many mL are in 1.63 L? 1 L = 1000 mL

  15. The speed of sound in air is about 343 m/s. What is this speed in miles per hour? meters to miles 1 mi = 1609 m seconds to hours 1 min = 60 s 1 hour = 60 min

  16. Important things to consider when solving problems and performing experiments….

  17. Volume – SI derived unit for volume is cubic meter (m3) 1 L = 1000 mL = 1000 cm3 = 1 dm3

  18. weight = c x mass A 1 kg bar will weigh on earth, c = 1.0 1 kg on earth on moon, c ~ 0.1 0.1 kg on moon Matter - anything that occupies space and has mass. mass – measure of the quantity of matter SI unit of mass is the kilogram (kg) weight – force that gravity exerts on an object

  19. mass density = volume A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass? m D = V Density – SI derived unit for density is kg/m3 1 g/cm3 = 1 g/mL = 1000 kg/m3 For Water: 1g/mL

  20. 0F = x 0C + 32 9 5 K = 0C + 273.15 273 K = 0 0C 373 K = 100 0C 32 0F = 0 0C 212 0F = 100 0C

  21. 0F – 32 = x 0C 0F = x 0C + 32 x (0F – 32) = 0C 5 5 5 0C = x (0F – 32) 0C = x (172.9 – 32) = 78.3 9 9 9 9 9 5 5 Convert 172.9 0F to degrees Celsius.

  22. Graphing Distance vs. Time Line of Best Fit DependentVariable Independent Variable

  23. Accuracy – how close a measurement is to the true value Precision – how close a set of measurements are to each other

  24. Percents and Percent Error • Percent Error: Measured Value - Accepted Value X 100 Accepted Value Example: The mass of a compound measured in a lab was 25.0 grams. The accepted value for this compound is 24.5 grams. Calculate the percent error. - 24.5 g 25.0 g X 100 = 2.04 % 24.5 g

  25. Scientific Method

  26. SCIENTIFIC METHOD logical approach to solving problems • Observation • Problem • Hypothesis • Experiment • Data • Analysis • Conclusion

  27. Observations • Qualitative: quality, non-numeric terms • Quantitative: quantity, numerical description

  28. MATTER Matter: anythingthat occupies space and has mass

  29. Three States of Matter Plasma

  30. Phase Changes liquid gas solid

  31. phase diagram: summarizes the conditions at which a substance exists as a solid, liquid, or gas. Phase Diagram of Water

  32. Phase Diagram Points • ________________: • above this point a substance becomes a supercritical fluid • critical temperature (Tc): temperature above which the gas cannot be made to liquefy, no matter how great the applied pressure. • critical pressure (Pc): minimum pressure that must be applied to bring about liquefaction at the critical temperature. • ________________: • point at which all three phases coexist

  33. Classification of Matter • Pure Substance: form of matter that has a definite composition and distinct properties 2. Mixture:combination of two or more substances in which the substances retain their own identities. water, ammonia, sucrose, gold, oxygen • mixed together physically • can usually be separated

  34. Examples: Types of Mixtures • Homogenous mixture – composition of the mixture is the same throughout. Examples: • Heterogeneous mixture – composition is not uniform throughout. 1.4

  35. Mixture Pictures

  36. Types of Mixtures • solution: mixture that remains uniformly mixed • solute: • solvent: • suspension:mixture where visible particles settle • colloid:mixture where particles are unevenly distributed but do not separate, positive Tyndall Effect

  37. Hom/Het? Soln/Susp/Coll? • Fog ____________ ___________ • Paint ____________ ___________ • Syrup ____________ ___________

  38. magnet distillation Physical means can be used to separate a mixture into its pure components. 1.4

  39. Methods of Separation PASTA/WATER SAND/IRON FILINGS SAND/WATER SALT /WATER FOOD COLORING/WATER BLOOD Strainer Filtration Physical Evaporation Centrifuge Distillation

  40. Element: • all atoms are the same • cannot be broken down by physical or chemical means • 114 elements named on the Periodic Table • 83 elements occur naturally on Earth gold, aluminum, lead, oxygen, carbon • many elements have been created by scientists technetium, americium, seaborgium

  41. Water (H2O) Glucose (C6H12O6) Ammonia (NH3) Compound: • 2 or more elements combined • Cannot be broken down by physical means • Can be broken down by chemical means • Appears different from original elements • Fixed ratios in definite proportions

  42. PHYSICAL AND CHEMICAL CHANGES

  43. Physical Properties and Physical Changes physical property: characteristic that can be observed or measured without changing the identity of the substance. physical change: change in a substance that does not involve a change in the identity of the substance.

  44. Physical Properties • Intensive: INDEPENDENT of amount of matter present (sample size) • Example: • Extensive: DEPENDENT on the amount of matter present (sample size) • Example:

  45. Chemical Properties and Chemical Changes • chemical property: a substance’s ability to undergo changes that transform it into different substances • Example: • chemical change: change in which one or more substances are converted into different substances • Example:

  46. Evidence of a Chemical Change

  47. sugar dissolving in water ice melting Physical or Chemical? hydrogen gas burns in oxygen gas to form water Remember: physical change does not alter the composition or identity of a substance. chemical change alters the composition or identity of the substance(s) involved.

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