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Chapter 1

Chapter 1. Introduction: Some Basic Concepts. Welcome to the World of Chemistry. Chemistry. The study of matter – its nature, its structure (how it is related to its atoms and molecules), properties, transformations, and its interactions with energy. Gold. Mercury. Matter.

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Chapter 1

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  1. Chapter 1 Introduction: Some Basic Concepts Welcome to the World of Chemistry

  2. Chemistry The study of matter – its nature, its structure (how it is related to its atoms and molecules), properties, transformations, and its interactions with energy Gold Mercury

  3. Matter Anything that has mass and occupies space

  4. Mass vs Weight • weight = force = mg g: gravitational acceleration • Mass is a measurement of the quantity of matter in a body or sample • Weight is the magnitude of Earth’s attraction to such a body or sample

  5. Physical States (Phases)Example of bromine, Br2, a halogen

  6. Solid • definite shape and volume • made of particles (atoms, molecules, or ions) held close together and rigidly in place • reasonably well understood. Example: Graphite — layer structure of carbon atoms reflects physical properties.

  7. Liquid • definite volume but indefinite shape • made of particles (atoms, molecules, or ions) held close together but allowed to move relative to each other • fluid and may not fill a container completely • not well understood

  8. Gas • indefinite volume and indefinite shape • the same shape and volume as their container • made of particles (atoms or molecules) separated from each other by large distances and that move very fast • fluid • good theoretical understanding

  9. Physical Property • characteristic of matter that can be observed without changing the basic identity of the matter • characteristics that are directly observable • eg. state, size, mass, V, color, odor, melting point (Tm), boiling point (Tb), density, solubility...

  10. Chemical Property • characteristic of matter that requires change in identity of the matter for observation (a chemical reaction) • characteristic that describes the behavior of matter • eg. flammability, corrosiveness, bleaching power, explosiveness, ...

  11. Scientific Method Observation Hypothesis * Law * Theory * experiment and then modify *

  12. Tro: Chemistry: A Molecular Approach Scientific Method Procedure designed to test an idea Tentative explanation of a single or small number of observations General explanation of natural phenomena Careful noting and recording of natural phenomena Generally observed occurrence in nature Tro: Chemistry: A Molecular Approach, 2/e

  13. Tro: Chemistry: A Molecular Approach Relationships Between Pieces of the Scientific Method Tro: Chemistry: A Molecular Approach, 2/e

  14. 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 • A theory is a unifying principle that explains a body of facts and the laws based on them. It is capable of suggesting new hypotheses.

  15. Classification of Matter

  16. Mixture • A combination of pure substances in which the components retain their identities (no reaction) • Can be separated into simpler mixtures and/or pure substances by

  17. Physical Separation Methods • mechanical: eg. sand and iron filings • filtration: eg. sand and water • extraction: eg. washing clothes, decaffeinating coffee • distillation • chromatography

  18. Distillation • Simple - for separation of volatile component from non-volatile component(s)

  19. Distillation • Fractional - for separation of multiple volatile components from each other. Employed in many chemistry labs, labs, and in crude oil refining.

  20. Chromatography • Mixture placed in mobile phase (gas or liquid). Mobile phase flows over and through stationary phase (solid or liquid). Mixture components separate based on relative affinity for mobile and stationary phases.

  21. Heterogeneous Mixture • inconsistent composition • atoms or molecules mixed not uniformly • contains regions within the sample with different characteristics • eg. pizza, carpet, beach sand, ... Homogeneous Mixture • solution • consistent composition throughout • atoms or molecules mixed uniformly • eg. air in a room, glass of tap water

  22. Compound • can be broken down to 2 or more elements by chemical means • constant composition • eg. water, H2O, by mass H:O = 1:8 hydrogen peroxide, H2O2, H:O = 1:16 • elements combined lose individual identities • more than 20 million compounds are now known

  23. Elements • basic substances of which all matter is composed • pure substances that cannot be decomposed by ordinary means to other substances. • made up of atoms • ~ 117 known at this time • given name and chemical symbol Aluminum Bromine

  24. Element Symbols • 1, 2 or 3 letters: • first letter always capitalized • usually first letter(s) of name H hydrogen C carbon O oxygen N nitrogen Na sodium Cl chlorine Mg magnesium Al aluminum P phosphorus K potassium Po polonium

  25. learn Latin names where appropriate, antimony - Sb - stibium gold - Au - aurum tungsten - W – wolfram sodium – Na – natrium potassium – K - kalium • elements from 104 to 111 are named after scientists; 112-118 have 3 letter symbols based on Latin name for number

  26. 112 Uub ununbium 113 Uut ununtrium 114 Uuq ununquadium 115 Uup ununpentium 116 Uuh ununhexium Homework: learn the names of first 36 elements in the periodic table

  27. Periodic Table • a listing of the elements arranged according to their atomic numbers, chemical and physical properties • VERY useful and important

  28. Physical Change • transformation of matter from one state to another that does not involve change in the identity of the matter • examples: boiling, subliming, melting, dissolving (forming a solution), ...

  29. Chemical Change • transformation of matter from one state to another that involves changing the identity of the matter • examples: rusting (of iron), burning (combustion), digesting, formation of a precipitate, gas forming, acid-base neutralization, displacing reactions...

  30. Intensive Property • independent of amount of matter • eg. density, temperature, concentration of a solution, specific heat capacity...

  31. Extensive Property • depends on amount of matter • eg. mass, volume, pressure, internal energy, enthalpy, ...

  32. Platinum Mercury Aluminum Density mass (g) mass (g) • Density =  =  volume (cm3) volume (mL) • density of H2O is 1.00 g/cm3 (pure water at ~ 4 °C) • 1cm3 = 1mL liquid 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3 They sink in water

  33. Know and Own and Practice Well • Metric System • SI Units • Unit Conversions • Learn a Conversion Factor Between English and Metric for • length, mass, volume, pressure

  34. SI Units • Système International d’Unités • A different base unit is used for each quantity.

  35. Prefixes A prefix • in front of a unit increases or decreases the size of that unit. • makes units larger or smaller than the initial unit by one or more factors of 10. • indicates a numerical value. prefix = value 1kilometer = 1000 meters 1 kilogram = 1000 grams

  36. Metric and SI Prefixes

  37. Learning Check Indicate the unit that matches the description. 1. A mass that is 1000 times greater than 1 gram. 1) kilogram 2) milligram 3) megagram 2. A length that is 1/100 of 1 meter. 1) decimeter 2) centimeter 3) millimeter 3. A unit of time that is 1/1000 of a second. 1) nanosecond 2) microsecond 3) millisecond

  38. Learning Check Select the unit you would use to measure A. your height. 1) millimeters 2) meters 3) kilometers B. your mass. 1) milligrams 2) grams 3) kilograms C. the distance between two cities. 1) millimeters 2) meters 3) kilometers D. the width of an artery. 1) millimeters 2) meters 3) kilometers

  39. Volume1 m = 10 dm(1m)3 = (10 dm)31m3 = 1000 dm3 = 1000 L 1 dm = 10 cm (1dm)3 = (10 cm)31dm3 = 1000 cm3 = 1000mL

  40. Equalities Equalities • use two different units to describe the same measured amount. • are written for relationships between units of the metric system, U.S. units, or between metric and U.S. units. For example, 1 in = 2.54 cm 1 m = 1000 mm 1 ft = 12 in 1 lb = 16 oz 1 mile = 5280 ft 2.205 lb = 1 kg 1 lb = 454 g 1 L = 1.057 qt 1 gal = 4 qt 1 hour = 60 min 1 cm3 = 1 cc = 1 mL 1 yd = 3 ft = 0.9144 m

  41. Conversion Factors A conversion factor • is a fraction obtained from an equality. Equality: 1 in. = 2.54 cm • is written as a ratio with a numerator and denominator. • can be inverted to give two conversion factors for every equality. 1 in.and2.54 cm 2.54 cm 1 in.

  42. Learning Check Write conversion factors for each pair of units. A. liters and mL Equality: 1 L = 1000 mL B. hours and minutes Equality: 1 hr = 60 min C. meters and kilometers Equality: 1 km = 1000 m D. micrograms and grams Equality: 1 µg = 10-6 g

  43. Conversion Factors in a Problem A conversion factor • may be obtained from information in a word problem. • is written for that problem only. Example 1: The price of one pound (1 lb) of red peppers is$2.39. 1 lb red peppers and $2.39 $2.39 1 lb red peppers Example 2: The cost of one gallon (1 gal) of gas is $3.95. 1 gallon of gas and $3.95 $3.95 1 gallon of gas

  44. Percent as a Conversion Factor A percent factor • gives the ratio of the parts to the whole. % = Parts x 100 Whole • uses the same unit to express the percent. • uses the value 100 and a unit for the whole. • can be written as two factors. Example: A food contains 30% (by mass) fat. 30 g fat or 100 g food 100 g food 30 g fat

  45. Density as a conversion factor Density of a mineral oil = 0.875 g/mL 0.875 g oil and 1 mL 1 mL 0.875 g oil

  46. Learning Check Write the equality and conversion factors for each of the following. A. square meters and square centimeters B. jewelry that contains 18% (by mass) gold C. One gallon of gas is $4.00

  47. Solving: Given and Needed Units To solve a problem • Identify the givenunit • Identify the needed unit. Example: A person has a height of 2.0 meters. What is that height in inches? The given unitis the initial unit of height. given unit = meters (m) The needed unitis the unit for the answer. needed unit = inches (in.)

  48. Problem Setup: Dimensional Analysis • Write the given and needed units. • Write a unit plan to convert the given unit to the needed unit. • Write equalities and conversion factors that connect the units. • Use conversion factors to cancel the given unit and provide the needed unit. Unit 1 x Unit 2 = Unit 2 Unit 1 Given x Conversion = Needed unit factor unit

  49. Setting up a Problem How many minutes are 2.5 hours? Given unit= 2.5 hr Needed unit = min Unit Plan= hr → min Setup problem to cancel hours (hr). Given Conversion Needed unit factor unit 2.5 hr x 60 min = 150 min (2 SF) 1 hr

  50. Learning Check A rattlesnake is 2.44 m long. How many centimeters long is the snake? 1) 2440 cm 2) 0.0244 cm 3) 24.4 cm 4) 244 cm

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