Patino_chm2040_chapt - Chapter 1 Chapter Introduction Some Basic Concepts Welcome to the World of Welcome Chemistry Chemistry Chemistry Chemistry

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Unformatted text preview: Chapter 1 Chapter Introduction: Some Basic Concepts Welcome to the World of Welcome Chemistry Chemistry Chemistry Chemistry The study of matter – its nature, its structure The (how it is related to its atoms and molecules), properties, transformations, and its interactions with energy and Gold Mercury Matter Matter Anything that has mass Anything and occupies space and Mass vs Weight Mass weight = force = mg g: gravitational acceleration g: s Mass is a measurement of the Mass quantity of matter in a body or sample sample s Weight is the magnitude of Earth’s Weight attraction to such a body or sample attraction s Physical States (Phases) Physical Solid Solid definite shape and volume s made of particles (atoms, molecules, or made ions) held close together and rigidly in place place s reasonably well understood. Example: s Graphite — layer structure of carbon atoms reflects physical properties. physical Liquid Liquid definite volume but definite indefinite shape indefinite s made of particles made (atoms, molecules, or ions) held close together but allowed to move relative to each other s fluid and may not fill a fluid container completely s not well understood not s Gas Gas s s s s s indefinite volume and indefinite indefinite shape indefinite the same shape and the volume as their container made of particles (atoms or made molecules) separated from each other by large distances and that move very fast very fluid good theoretical good understanding understanding Physical Property Physical s s s characteristic of matter characteristic that can be observed without changing the basic identity of the matter matter characteristics that are characteristics directly observable directly eg. state, size, mass, eg. V, color, odor, melting point (Tm), boiling point point ), (Tb), density, (T ), solubility... solubility... Chemical Property Chemical characteristic of matter that requires characteristic change in identity of the matter for observation (a chemical reaction) s characteristic that describes the characteristic behavior of matter behavior s s eg. flammability, corrosiveness, eg. bleaching power, explosiveness, ... bleaching Scientific Method Scientific Observation Hypothesis * Law * * Theory * experiment and then modify experiment s s s Hypothesis – a tentative interpretation or explanation for an observation explanation – falsifiable – confirmed or refuted by other falsifiable observations observations – tested by experiments – validated or tested invalidated invalidated when similar observations are consistently when made, it can lead to a Scientific Law Scientific – a statement of a behavior that is always statement observed observed – summarizes past observations and summarizes predicts future ones predicts – 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. It Classification of Matter Classification Mixture Mixture A combination of pure substances in combination which the components retain their identities (no reaction) identities s Can be separated into simpler Can mixtures and/or pure substances by mixtures s Physical Separation Methods Physical s s s s s mechanical: eg. sand and iron filings filtration: eg. sand and water extraction: eg. washing clothes, decaffeinating extraction: coffee coffee distillation chromatography Distillation Distillation s Simple - for separation of volatile component Simple from non-volatile component(s) from Distillation Distillation s Fractional - for separation of multiple Fractional volatile components from each other. Employed in many chemistry labs, labs, and in crude oil refining. labs, Chromatography Chromatography s Mixture placed in mobile phase (gas Mixture 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. mobile Heterogeneous Mixture Heterogeneous inconsistent composition inconsistent s atoms or molecules mixed not uniformly s contains regions within the sample with contains different characteristics different s eg. pizza, carpet, beach sand, ... s Homogeneous Mixture solution s consistent composition throughout consistent s atoms or molecules mixed uniformly s eg. air in a room, glass of tap water s Compound Compound can be broken down to 2 or more can elements by chemical means elements s constant composition s eg. water, H2O, by mass H:O = 1:8 s hydrogen peroxide, H2O2, H:O = 1:16 hydrogen elements combined lose individual elements identities identities s more than 20 million compounds are more now known now s Elements Elements s s s s s basic substances of basic which all matter is composed composed pure substances that pure cannot be decomposed by ordinary means to ordinary other substances. other made up of atoms ~ 117 known at this time given name and chemical given symbol symbol Aluminum Bromine Element Symbols Element 1, 2 or 3 letters: 1, s first letter always capitalized first always s usually first letter(s) of name s H hydrogen C carbon O oxygen N nitrogen oxygen nitrogen Na sodium Cl chlorine Mg magnesium Al aluminum P phosphorus K potassium Po polonium Po learn Latin names where appropriate, learn antimony - Sb - stibium antimony gold - Au - aurum gold tungsten - W – wolfram tungsten sodium – Na – natrium sodium potassium – K - kalium potassium s elements from 104 to 111 are named elements after scientists; 112-118 have 3 letter symbols based on Latin name for number number s 112 112 113 114 115 116 Uub Uut Uuq Uup Uuh ununbium ununtrium ununquadium ununpentium ununhexium Homework: learn the names of first 36 elements in the periodic table first Periodic Table Periodic a listing of the elements arranged listing according to their atomic numbers, chemical and physical properties chemical s VERY useful and important s Physical Change Physical transformation of matter from one transformation state to another that does not involve change in the identity of the matter change s examples: boiling, subliming, examples: melting, dissolving (forming a solution), ... solution), s Chemical Change Chemical s s transformation of matter from one state to another transformation that involves changing the identity of the matter that examples: rusting (of iron), burning (combustion), examples: digesting, formation of a precipitate, gas forming, acid-base neutralization, displacing reactions... acid-base Intensive Property Intensive independent of amount of matter s eg. density, temperature, eg. concentration of a solution, specific heat capacity... heat s Extensive Property Extensive depends on amount of matter s eg. mass, volume, pressure, internal eg. energy, enthalpy, ... energy, s Density Density s s s mass (g) mass (g) mass Density = = Density volume (cm3) volume (mL) volume density of H2O is 1.00 g/cm3 (pure water at ~ 4 °C) (pure 1cm3 = 1mL Mercury Platinum Aluminum liquid 13.6 g/cm3 21.5 g/cm3 They sink in water 2.7 g/cm3 Know and Own and Practice Well Well Metric System s SI Units s Unit Conversions s Learn a Conversion Factor Between Learn English and Metric for English – length, mass, volume, pressure s Prefixes Prefixes A prefix prefix n s iin front of a unit increases or decreases the size of that unit. s makes units larger or smaller than the initial unit makes by one or more factors of 10. s indicates a numerical value. prefix 1 kilometer kilo = = value 1000 meters 1000 1 kilogram kilo = 1000 grams grams Metric and SI Prefixes Metric Learning Check Learning Indicate the unit that matches the description. 1. A mass that is 1000 times greater than 1 1. gram. gram. 1) kilogram 2) milligram 3) megagram 1) 2. A length that is 1/100 of 1 meter. 1) decimeter 2) centimeter 3) millimeter 1) 3. A unit of time that is 1/1000 of a second. 1) nanosecond 2) microsecond 3) millisecond 3) Learning Check Learning Select the unit you would use to measure Select A. your height. A. 1) millimeters 2) meters 1) 3) kilometers B. your mass. B. 1) milligrams 2) grams 1) 3) kilograms C. the distance between two cities. 1) millimeters 2) meters 3) kilometers 1) D. the width of an artery. 1) millimeters 2) meters 1) 3) kilometers Volume Volume 1 m = 10 dm 10 (1m)3 = (10 dm)3 1m3 = 1000 dm3 = 1000 L 1m 1 dm = 10 cm (1dm)3 = (10 cm)3 1dm3 = 1000 cm3 = 1000mL Equalities Equalities Equalities • use two different units to describe the same use measured amount. • are written for relationships between units of are the metric system, U.S. units, or between metric and U.S. units. For example, 1m = 1000 mm 1000 1 llb b = 16 oz 2.205 lb = 1 kg 1L = 1.057 qt 1 hour = 60 min Conversion Factors Conversion A conversion factor conversion • is a fraction obtained from an equality. Equality: 1 in. = 2.54 cm in. s • iis written as a ratio with a numerator and denominator. denominator. • can be inverted to give two conversion factors can for every equality. for 1 in. and 2.54 cm in. and 2.54 cm 1 in. 2.54 Learning Check Learning 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 C. Equality: Equality: 1 km = 1000 m D. micrograms and grams Equality: Equality: 1 µg = 10-6 g Conversion Factors in a Problem Conversion A conversion factor conversion • may be obtained from information in a word may problem. problem. s • iis written for that problem only. for Example 1: Example The price of one pound (1 lb) of red peppers is one $2.39. $2.39. 1 lb red peppers and $2.39 $2.39 $2.39 1 lb red peppers $2.39 Example 2: The cost of one gallon (1 gal) of gas is $3.95. one $3.95. 1 gallon of gas and $3.95 $3.95 $3.95 1 gallon of gas $3.95 Percent as a Conversion Factor Percent A percent factor percent • 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. can Example: A food contains 30% (by mass) fat. Example: 30 g fat 100 g food and 100 g food 30 g fat Density as a conversion factor Density Density of a mineral oil = 0.875 g/mL 0.875 g oil 1 mL mL and 1 mL mL 0.875 g oil Learning Check Learning 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 Solving: Given and Needed Units Given To solve a problem dentify • IIdentify the given unit given unit dentify • IIdentify the needed unit. needed Example: A person has a height of 2.0 meters. What is that height in inches? What The given unit is the initial unit of height. given given unit = meters (m) given The needed unit is the unit for the needed answer. answer. needed unit = inches (in.) needed Problem Setup: Dimensional Analysis Dimensional • Write the given and needed units. • Write a unit plan to convert the given unit Write to the needed unit. to • Write equalities and conversion factors Write that connect the units. that • Use conversion factors to cancel the given Use unit and provide the needed unit. unit Unit 1 Unit x Given Given unit x Unit 2 = Unit 2 Unit Unit 1 Unit Conversion = Needed Conversion factor unit Setting up a Problem Setting How many minutes are 2.5 hours? Given unit = 2.5 hr 2.5 Needed unit = min Unit Plan = hr → min Setup problem to cancel hours (hr). Setup Given Conversion Needed Given unit factor unit 2.5 hr x 60 min = 150 min (2 SF) 2.5 1 hr hr Learning Check Learning A rattlesnake is 2.44 m long. How many centimeters long is the snake? 1) 2440 cm 1) 2440 2) 0.0244 cm 3) 24.4 cm 4) 244 cm 4) Using Two or More Factors Using • Often, two or more conversion factors are Often, required to obtain the unit needed for the answer. required Unit 1 Unit → Unit 2 → Unit 3 Unit • Additional conversion factors are placed in the Additional setup to cancel each preceding unit setup Given unit x factor 1 x factor 2 = needed unit Given needed Unit 1 x Unit 2 Unit Unit 1 Unit x Unit 3 Unit Unit 2 = Unit 3 Unit Example: Problem Solving Example: How many minutes are in 1.4 days? Given unit: 1.4 days Given Factor 1 Factor Plan: Plan: days → Factor 2 hr → min Set up problem: Set 1.4 days x 24 hr x 60 min = 2.0 x 103 min 24 60 min 1day 1 hr 1day 2 SF SF Exact Exact = 2 SF SF Learning Check Learning A bucket contains 4.65 L of water. How bucket many many gallons of water is that? Unit plan: L → qt → gallon Equalities: 1.06 qt = 1 L Set up Problem: Set 4.65 L x 4.65 3 SF 1.06 qt 1L Exact 1 gal = 4 qt x 1 gal = 1.23 gal gal 4 qt Exact 3 SF Learning Check Learning If a ski pole is 3.0 feet in length, how long is the ski If pole in mm? Solution: Solution: 3.0 ft x 3.0 12 in x 2.54 cm x 10 mm = 2.54 10 1 ft 1 in. 1 cm ft Calculator answer: 914.4 mm Calculator Needed answer: 910 mm (2 SF rounded) Needed Check factor setup: Units cancel properly Check Units Check needed unit: mm Learning Check Learning If your pace on a treadmill is 65 meters per minute, how many minutes will it take for you to walk a distance of 7500 feet? Solution: Solution: Given: 7500 ft 65 m/min Needed: min Plan: ft → in. → cm → m → min Equalities: 1 ft = 12 in. 1 in. = 2.54 cm 1 m = 100 cm 1 min = 65 m (walking pace) min Set Up Problem: 7500 ft x 12 in. x 7500 12 1 ft ft 2.54 cm x 1m x 1 min 2.54 min 1 in. 100 cm 65 m = 35 min final answer (2 SF) 35 final (# 11): Ethylene glycol, C2H6O2, iis an ingredient of s (# automobile antifreeze. Its density is 1.11 g/cm3 at 20 automobile °C. If you need exactly 500. mL of this liquid, what mass of the compound, in grams, is required? mass Needed: m(g) Given: d(g/cm3) and V(mL) 1 cm3 = 1 mL cm 1.11 g 1.11 500. mL × ───── = 555 g 500. ───── 1 mL 3 SF SF (# 13): A chemist needs 2.00 g of a liquid compound with a density of 0.718 g/cm3. What volume of the with What compound is required? compound Needed: V(cm3) Given: d(g/cm3) and m(g) 1 cm3 cm 2.00 g × ────── = 2.78 cm3 ────── 0.718 g 3 SF SF (# 15): A sample of 37.5 g of unknown metal is placed in a graduated cylinder containing water. The levels of the water before and after adding the sample are 7.0 and 20.5 mL respectively. Which metal in the following list is most likely the sample? likely Metal d(g/mL) Metal d(g/mL) Mg Mg 1.74 Al 2.70 Fe Fe 7.87 Cu 8.96 Ag Ag 10.5 Pb 11.3 11.3 The volume of sample = volume of water displaced in cylinder = 20.5 – 7.0 = 13.5 mL displaced one dec. place one After After placing the piece of metal metal Before Before (# 15): (# Needed: d(g/cm3) Given: V(mL) and m(g) m 37.5 g 37.5 d = ── = ────── = 2.78 g/mL ── ────── V 13.5 mL 13.5 3 SF SF From the list, the metal is Al. s Accuracy: nearness of the nearness measurement to accepted value of the quantity. the s Precision: reproducibility; how well reproducibility; several determinations of the same quantity agree. quantity Consider a sample that was analyzed for lead content and was known to contain 49.3 ppm ppm lead. Two analyses lead. Two Analysis A Analysis B diff. from Analysis diff. Trial ppm Pb Trial ppm Pb Trial average average 1 38.9 1 48.9 4.6 2 23.2 2 59.8 6.3 3 55.9 3 54.5 1.0 4 80.1 4 49.0 4.5 5 46.9 5 55.3 1.8 46.9 average = 49.0 ppm Pb 53.5 ppm average diff. 15.5 ppm 3.6 ppm Numbers Numbers magnitude, value s direction: sign (+ or −) s type of measurement: units s precision of original measurement: precision significant figures significant s Measured Numbers Measured A measuring tool measuring is used to determine a quantity such as height or the mass of an object. of • provides numbers provides for a measurement called measured numbers. numbers Reading a Meter Stick Reading . l2. . . . l . . . . l3 . . . . l . . . . l4. . cm cm • The markings on the meter stick at the end The of the orange line are read as of the first digit 2 the • • plus the second digit 2.7 The last digit is obtained by estimating. The estimating The end of the line might be estimated between 2.7–2.8 as half-way (0.5) or a little more (0.6), which gives a reported length of 2.75 cm or 2.76 cm. of Known & Estimated Digits Known In the length reported as 2.76 cm, In • The digits 2 and 7 are certain The • • (known). The final digit 6 was estimated The (uncertain). All three digits (2.76) are All significant including the estimated digit. digit. Significant Figures in Measured Numbers Measured Significant figures • obtained from a measurement obtained include all of the known digits plus the estimated digit. plus • reported in a measurement reported depend on the measuring tool. depend Significant Figures Significant Examples of Counting SF Examples 143.22 s 143.0 s 300592 s 0.0020930 s 100.0 s 100. s 100 s s s Exact numbers have an unlimited number of significant figures A number whose value is number known with complete certainty is exact exact – from counting individual from objects objects – from definitions 1 cm is exactly equal to 0.01 m – from integer values in from equations equations in the equation for the radius in of a circle, the 2 is exact of SF in Calculations SF Addition and/or Subtraction s perform operation s round answer to same number of round digits after decimal as number in calculation with the fewest calculation Example Example 132.09 + 35.94376 – 0.0173 = 132.09 + 35.94376 – 0.0173 = 132. 168.01646 168.01646 must have 2 digits after decimal 168.02 Multiplication and/or Division Division s perform operation(s) s round answer to same number of round significant figures as number in the calculation with the fewest calculation Example Example (26.894)(0.0837)/13 = (26.894)(0.0837)/13 (26.894)(0.0837) = 0.1731560 (26.894)(0.0837) 13 13 must have 2 SF 0.17 Log and/or Antilog Log number of digits in mantissa of log = number digits number of significant figures in antilog in Example Example log (14.8003) = log log (14.8003) = 1.17027051857 log antilog antilog 1.170271 1. mantissa mantissa Rounding Rounding s if if first digit to be eliminated is ≥ 5, round preceding digit up one round s if if first digit to be eliminated is <5, truncate truncate Examples Examples Round each of the following to 4 SF Round SF s 10.02700 10.03 10.03 s 10.02495 10.02 10.02 s 10.02502 10.03 10.03 10.02500 10.03 10.03 s 10.01500 10.02 10.02 s 10.02500000000000000000000001 10.03 10.03 s Exponentials Exponentials Scientific notation: very large or very small Scientific numbers are expressed in the following general form: exponent term, n = ± integer integer N x 10n 10 digit term, between ± 1 and 9.9999… (coefficient) (coefficient) eg eg −12,760,000 = −1.276 x 10 7 0.000012760 = 1.2760 x 10-5 0.000012760 Write the following in scientific notation: Write 22,400 = 2.24 x 104 22,400 2.24 22,400. = 2.2400 x 104 22,400. 2.2400 892 x 105 = 8.92 x 107 8.92 -0.00198 x 10-10 = -1.98 x 10-13 -1.98 127.60 x 10-5 = 1.2760 x 10-3 1.2760 Write in fixed notation: Write 5.720 x 10-2 = 0.05720 5.720 0.05720 -1.982 x 104 = -19,820 -19,820 Exponentials in calculations Exponentials 5.750 x 103 + 7.25 x 102 = 1.75 x 10-3 x 6.45 x 102 57.50 x 102 + 7.25 x 102 57.50 = 1.75 x 10-3 x 6.45 x 102 64.75 x 102 64.75 = 1.75 x 10-3 x 6.45 x 102 64.75 1.75 x 6.45 x 102 10-3 x 102 = 5.74 x 103 5.74 3 SF SF (0.000345 – 0.0001273) x 6.730x10 3 (0.000345 = 154.00 6 dec places (we keep the 77, though) 0.0002177 x 6.730x103 0.000217 = 154.00 154.00 2.177 has 3 SF only 2.17 has 2.177x10−4 x 6.730x103 2.17 = 0.009513 = 9.51x10−3 0.00951 1.5400 x 102 3 SF 1.5400 SF Temperature Temperature Temperature Temperature s • iis a measure of how hot or cold an object is compared to another object. to ndicates • iindicates that heat flows from the object with a higher temperature to the object with a lower temperature. s • iis measured using a thermometer. thermometer. Temperature Scales Temperature Temperature Temperature Scales Scales s are Fahrenheit, Celsius, and Kelvin. s have reference points for the boiling and freezing points of water. Temperature Scales Temperature s Fahrenheit (°F ) s Celcius or Centigrade (°C ) s 9 °F = ── °C +32 = 1.8 °C + 32 °F ── 5 s 5 (°F - 32) (°F °C = (°F -32) = °C 9 1.8 1.8 s K = °C + 273 °C Kelvin (K) 273.15 (exact) ΔT(K) = ΔT(°C) variation of temperature K) Learning check Learning a. The normal temperature of a chickadee is 105.8°F. What is that temperature on the Celsius scale? Celsius 1) 73.8°C 2) 58.8°C 3) 41.0°C 3) b. A pepperoni pizza is baked at 235°C. What temperature is needed on the Fahrenheit temperature Fahrenheit scale? 1) 267°F 2) 508°F 3) 455°F 1) 3) c. Convert 204.3 K into °C. Other elements to remember remember Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn s Ru, Rh, Pd, Ag, Cd s Pt, Au, Hg s ...
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This note was uploaded on 11/07/2011 for the course CHM 2045 taught by Professor Geiger during the Fall '08 term at University of Central Florida.

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