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Chemistry: The Study of Change Chapter 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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2 Chemistry: A Science for the 21 st Century Health and Medicine Sanitation systems Surgery with anesthesia Vaccines and antibiotics Gene therapy Energy and the Environment Fossil fuels Solar energy Nuclear energy

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3 Chemistry: A Science for the 21 st Century Materials and Technology Polymers, ceramics, liquid crystals Room-temperature superconductors? Molecular computing? Food and Agriculture Genetically modified crops “Natural” pesticides Specialized fertilizers

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4 The Study of Chemistry MacroscopicMicroscopic

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5 Qualitative data consists of general observations about the system Quantitative data comprises numbers obtained by various measurements of the system. The coffee is hot The boy is tall The coffee is heated to 97°C John is 5 ft 6 in tall

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6 The scientific method is a systematic approach to research A hypothesis is a tentative explanation for a set of observations tested modified

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7 A theory is a unifying principle that explains a body of facts and/or those laws that are based on them. A law is a concise statement of a relationship between phenomena that is always the same under the same conditions. Atomic Theory Force = mass x acceleration

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Problem 1.3 Classify the following statement as (a) qualitative (b) quantitative 1.The sun is approximately 93 million miles from earth. 2. Leonardo daVinci was a better painter than Michelangelo. 3.Ice is less dense than water. 4.Butter tastes better than margarine. 8

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Problem 1.4 (a) Classify the following statement as a (a) hypothesis (b) law (c) theory 1.Beethoven’s contribution to music would have been much greater if he had married. 2. An autumn leaf gravitates toward the ground because there is an attractive force between the leaf and the earth. 3. All matter is composed of very small particles called atoms 9

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10 Matter is anything that occupies space and has mass. A substance is a form of matter that has a definite composition and distinct properties. Chemistry is the study of matter and the changes it undergoes liquid nitrogen gold ingots silicon crystals

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11 A mixture is a combination of two or more substances in which the substances retain their distinct identities. 1. Homogenous mixture – composition of the mixture is the same throughout. 2. Heterogeneous mixture – composition is not uniform throughout. clear juice (apple, cranberry), bronze, solder cement, iron filings in sand

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

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13 A compound is a substance composed of atoms of two or more elements chemically united in fixed proportions. Compounds can only be separated into their pure components (elements) by chemical means. lithium fluoride quartz dry ice – carbon dioxide

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14 An element is a substance that cannot be separated into simpler substances by chemical means. 114 elements have been identified 82 elements occur naturally on Earth gold, aluminum, lead, oxygen, carbon, sulfur 32 elements have been created by scientists technetium, americium, seaborgium Element 118 discovered in 2006!

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16 Classifications of Matter

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Problem 1.16(a) Classify the following as a(n) (a) element (c) homogeneous mixture (b) compound (d) heterogeneous mixture filtered sea water Helium gas Kosher salt (sodium chloride) A bottle of soda (capped, unshaken) A milkshake Filtered air in a bottle concrete 17

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18 A Comparison: The Three States of Matter

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19 The Three States of Matter: Effect of a Hot Poker on a Block of Ice solid liquid gas

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20 A physical change does not alter the composition or identity of a substance. A chemical change alters the composition or identity of the substance(s) involved. ice melting sugar dissolving in water hydrogen burns in air to form water Types of Changes

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Problem 1.12(a) Does the following describe a (a) chemical change or a (b) physical change? 1.The helium gas inside of a balloon tends to leak out after a few hours. 2.Frozen orange juice is reconstituted by adding water to it. 3.The growth of plants depends on the sun’s energy in a process called photosynthesis. 4.A spoonful of table salt dissolves in a bowl of soup. 21

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22 An extensive property of a material depends upon how much matter is is being considered. An intensive property of a material does not depend upon how much matter is is being considered. mass length volume density temperature color Extensive and Intensive Properties

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23 Matter - anything that occupies space and has mass. mass – measure of the quantity of matter SI unit of mass is the kilogram (kg) 1 kg = 1000 g = 1 x 10 3 g weight – force that gravity exerts on an object W = m x a SI unit of force is the Newton (N) 1 N = 1 kg∙m/s 2 Interestingly, the process of measuring mass is called weighing!

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24 Mass is constant, while weight is dependent on location On earth, a = 9.81 m/s 2 W = 1 kg x 9.81 m/s 2 = 9.81 kg∙m/s Newton 9.81 Newton/1.67 Newton = 5.87 A 1 kg mass weighs almost 6 times more on earth than on the moon! On the moon, a = 1.67 m/s 2 W = m x a = 1 kg x 1.67 m/s Newton

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25 International System of Units (SI)

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27 Volume – SI derived unit for volume is cubic meter (m 3 ) 1 cm 3 = (1 x m) 3 = 1 x m 3 1 dm 3 = (1 x m) 3 = 1 x m 3 1 L = 1000 mL = 1000 cm 3 = 1 dm 3 1 mL = 1 cm 3

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28 Density – SI derived unit for density is kg/m 3 1 g/cm 3 = 1 g/mL = 1000 kg/m 3 density = mass volume d = m V A piece of platinum metal with a density of 21.5 g/cm 3 has a volume of 4.49 cm 3. What is its mass?

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Problem 1.22 The density of ethanol, a colorless liquid that is commonly known as grain alcohol, is g/mL. Calculate the mass of 17.4 mL of the liquid. 29

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31 K = ( 0 C C) 0 F = x 0 C F 9 0 F 5 0 C 273 K = 0 0 C 373 K = C 32 0 F = 0 0 C F = C A Comparison of Temperature Scales 1K 1 0 C

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32 Convert C to degrees Fahrenheit. Convert F to degrees Celsius. Convert 77 K, the boiling point of liquid nitrogen to degrees Celsius.

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Problem 1.24(a) Normally the human body can endure a temperature of 105 °F for only short periods of time without permanent damage to the brain and other vital organs. What is the temperature in °C? 33

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Problem 1.24(b) Ethylene glycol is a liquid organic compound that is used as an antifreeze in car radiators. It freezes at °C. Calculate the freezing point in °F. 34

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Problem 1.24(c) The temperature of the surface of the sun is about 6300 °C. What is this temperature is °F? 35

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Problem 1.24(d) The ignition temperature of paper is 451 °F. What is the temperature in K? 36

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37 Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000, x The mass of a single carbon atom in grams: x N x 10 n N is a number between 1 and 10 n is a positive or negative integer

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38 Scientific Notation n > = x 10 2 move decimal left n < = 7.72 x move decimal right Addition or Subtraction 1.Write each quantity with the same exponent n 2.Combine N 1 and N 2 3.The exponent, n, remains the same 4.31 x x 10 3 = 4.31 x x 10 4 = 4.70 x 10 4

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39 Scientific Notation Multiplication 1.Multiply N 1 and N 2 2.Add exponents n 1 and n 2 (4.0 x ) x (7.0 x 10 3 ) = (4.0 x 7.0) x ( ) = 28 x = 2.8 x Division 1.Divide N 1 and N 2 2.Subtract exponents n 1 and n x 10 4 ÷ (5.0 x 10 9 )= (8.5 ÷ 5.0) x = 1.7 x 10 -5

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40 Significant Figures Any digit that is not zero is significant kg 4 significant figures Zeros between nonzero digits are significant 606 m 3 significant figures Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure If a number is greater than 1, then all zeros to the right of the decimal point are significant 2.0 mg 2 significant figures If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant g 3 significant figures

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41 How many significant figures are in each of the following measurements? 24 mL 3001 g m x 10 4 molecules 560 kg

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Problem 1.34 How many significant figures are in each of the following measurements? a)0.006 L b) dm c)60.5 mg d)605.5 cm 2 e)960 x g f)6 kg g)60 m 42

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43 Significant Figures Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers round off to 90.4 one significant figure after decimal point two significant figures after decimal point round off to 0.79

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44 Significant Figures Multiplication or 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 = = sig figsround to 3 sig figs 6.8 ÷ = sig figsround to 2 sig figs = 0.061

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45 Significant Figures Exact Numbers Numbers from definitions or counted numbers of objects are considered to have an infinite number of significant figures The average of three measured lengths; 6.64, 6.68 and 6.70? = = 6.67 Because 3 is an exact number = 7

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46 Carry out the following arithmetic operations to the correct number of significant figures. 11,254.1 g g L – L 8.16 m x kg ÷ 88.3 mL 2.64x10 3 cm x10 2 cm

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47 Carry out the following arithmetic operations to the correct number of significant figures L L 9.1 g – g 7.1x10 4 dm x x10 2 dm 6.54 g ÷ mL 7.55x10 4 m – 8.62x10 3 m

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Problem 1.36 Carry out the following operations as if they were calculations of experimental results, and express each answer in the correct units with the correct number of significant figures a)7.310 km ÷ 5.70 km b)(3.26 x mg) – (7.88 x ) mg c)(4.02 x 10 6 dm) + (7.74 x 10 7 dm) d)(7.8 m – 0.34 m)/(1.15 s s) 48

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49 Accuracy – how close a measurement is to the true value Precision – how close a set of measurements are to each other accurate & precise but not accurate & not precise

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Problem 1.38 Three apprentice tailors (X,Y, and Z) are assigned to the task of measuring the seam of a pair of trousers. The results in inches are: X (31.5, 31.6, 31.4) Y (32.8, 32.3, 32.7) Z (31.9, 32.2, 32.1) The true length is 32.0 in. Comment on the precision and accuracy of each tailor’s measurements. 50

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51 Dimensional Analysis Method of Solving Problems 1.Determine which unit conversion factor(s) are needed 2.Carry units through calculation 3.If all units cancel except for the desired unit(s), then the problem was solved correctly. given quantity x conversion factor = desired quantity given unit x = desired unit desired unit given unit

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52 Dimensional Analysis Method of Solving Problems Conversion Unit 1 L = 1000 mL 1L 1000 mL 1.63 L x = 1630 mL 1L 1000 mL 1.63 L x = L2L2 mL How many mL are in 1.63 L?

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53 The speed of sound in air is about 343 m/s. What is this speed in miles per hour? 1 mi = 1609 m1 min = 60 s1 hour = 60 min 343 m s x 1 mi 1609 m 60 s 1 min x 60 min 1 hour x = 767 mi hour meters to miles seconds to hours conversion units

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Problem 1.46 The current speed limit in some states in the US is 55 miles per hour. What is the speed limit in km/hr? (1 mi = 1609 m) 54

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Problem 1.66 Vanillin is the substance whose aroma the human nose detects in the smallest amount. The threshold limit is 2.0 x g per liter of air. If the current price of 50 g of vanillin is $112, determine the cost (in cents) to supply enough vanillin so that the aroma could be detected in a large aircraft hanger with a volume of 5.0 x 10 7 ft 3 55

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