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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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1. Matter is anything that occupies space and has mass. 2. 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 water, ammonia, sucrose, gold, oxygen 1.4

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Three States of Matter 1.5

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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. soft drink, milk, solder cement, iron filings in sand 1.4

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

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Physical or Chemical? 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 gas burns in oxygen gas to form water 1.6

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An element is a substance that cannot be separated into simpler substances by chemical means. 115 elements have been identified 83 elements occur naturally on Earth gold, aluminum, lead, oxygen, carbon 32 elements have been created by scientists technetium, americium, seaborgium 1.4

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Periodic Chart of the elements

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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. Water (H 2 O)Glucose (C 6 H 12 O 6 ) Ammonia (NH 3 ) 1.4

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Table 1.2 SI Base Units Base QuantityName of UnitSymbol Lengthmeterm Masskilogramkg Timeseconds CurrentampereA TemperaturekelvinK Amount of substancemolemol Luminous intensitycandelacd 1.7

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Table 1.3 Prefixes Used with SI Units PrefixSymbolMeaning Tera-T10 12 Giga-G10 9 Mega-M10 6 Kilo-k10 3 Deci-d10 -1 Centi-c10 -2 Milli-m10 -3 Micro- 10 -6 Nano-n10 -9 Pico-p10 -12 1.7

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Volume – SI derived unit for volume is cubic meter (m 3 ) 1 L = (10 cm) 3 = 1000 cm 3 1 cm 3 = 1/1000 L = 1 mL = 1 cc 1.7

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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 1.7 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? d = m V m = d x V = 21.5 g/cm 3 x 4.49 cm 3 = 96.5 g

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K = 0 C + 273.15 1.7 273 K = 0 0 C 373 K = 100 0 C 32 0 F = 0 0 C 212 0 F = 100 0 C 0 C = x ( 0 F – 32) 9 5

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Convert 172.9 0 F to degrees Celsius. 0 C = x ( 0 F – 32) 9 5 0 C = x (172.9 – 32) = 78.28 9 5 1.7

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A substance is characterized and identified by its own unique set of physical and chemical properties A physical property can be measured without changing the identity of the substance. A chemical property can only be measured by changing the identity of the substance. The measurement process only involves physical changes (or no change) in the substance being measured. The measurement or observation requires a chemical change in the substance, which is consumed in the process to form new substances.

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Iron rusts. Peroxide lightens dark hair. The density of iron is 7.86 g/cm 3. The boiling point temperature of water is 100 o C at sea level. A piece of chalk is white. Physical vs. Chemical property? Measured by reacting iron with oxygen, using up iron and generating rust (iron oxide). chemical Measured by looking at chalk. Chalk is completely unaltered by process. physical Peroxide reacts with hair pigments, transforming them into colorless substances. chemical Measured by first weighing iron, then measuring dimensions of sample with calipers. physical Measured by boiling water into steam, a phase change of water. physical

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Properties can also be classified as either intensive or extensive. An extensive property depends on the amount of material present. An intensive property does not depend on the amount of material present, only on the identity of the substance. Generally, if the amount of material present is increases (doubles, for example), the extensive property also increases proportionally (doubles). A larger or smaller sample of the substance will exhibit the same property. We use intensive properties to identify substances. Chemical properties are almost always intensive.

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A chunk of iron weight 5.2 lbs. A bucket of water has a volume of 10.4 liters. The density of iron is 7.86 g/cm 3. The boiling point temperature of water is 100 o C at sea level. A piece of chalk is white. Extensive vs. Intensive property? A bigger chunk of iron will have a proportionately greater weight. Weight is an extensive property. A small piece of chalk and a large piece of chalk will both be white. Color is an intensive property. More water would take up a larger volume and need a larger bucket. Volume is an extensive property. If the volume doubles, the mass would too. The density would be the same. Density is an intensive property. A cup of water and a barrel of water would both boil at the same temperature. Boiling point temperature is an intensive property.

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

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Scientific Notation 1.8 568.762 n > 0 568.762 = 5.68762 x 10 2 move decimal left 0.00000772 n < 0 0.00000772 = 7.72 x 10 -6 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 10 4 + 3.9 x 10 3 = 4.31 x 10 4 + 0.39 x 10 4 = 4.70 x 10 4

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Scientific Notation 1.8 Multiplication 1.Multiply N 1 and N 2 2.Add exponents n 1 and n 2 (4.0 x 10 -5 ) x (7.0 x 10 3 ) = (4.0 x 7.0) x (10 -5+3 ) = 28 x 10 -2 = 2.8 x 10 -1 Division 1.Divide N 1 and N 2 2.Subtract exponents n 1 and n 2 8.5 x 10 4 ÷ 5.0 x 10 9 = (8.5 ÷ 5.0) x 10 4-9 = 1.7 x 10 -5

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How many significant figures are in each of the following measurements? 24 mL2 significant figures 3001 g 4 significant figures 0.0320 m 3 3 significant figures 6.4 x 10 4 molecules 2 significant figures 560 kg2 significant figures 1.8

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Significant Figures 1.8 Any digit that is not zero is significant 1.234 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 0.00420 g 3 significant figures

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Significant Figures 1.8 Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers. 89.332 1.1+ 90.432 round off to 90.4 one significant figure after decimal point 3.70 -2.9133 0.7867 two significant figures after decimal point round off to 0.79

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Significant Figures 1.8 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 3.6666 = 16.536366= 16.5 3 sig figsround to 3 sig figs 6.8 ÷ 112.04 = 0.0606926 2 sig figsround to 2 sig figs = 0.061

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Significant Figures 1.8 Exact Numbers Numbers from definitions or 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? 6.64 + 6.68 + 6.70 3 = 6.67333 = 6.67 Because 3 is an exact number = 7 Note: averages are rounded off to the same precision as the original set of numbers, not as per rule of addition for sig figs.

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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 1.8

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Useful Conversion Factors 1 miles = 1609 m = 1.609 km 1 hour = 60 min 1 min = 60 s 1 lbs (of mass) = 454 g 1 in = 2.54 cm 1 ft = 0.3048 m C = 3.00 x 108 m/s

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1.9 Factor-Label 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. 1 L = 1000 mL How many mL are in 1.63 L? 1L 1000 mL 1.63 L x = 1630 mL 1L 1000 mL 1.63 L x = 0.001630 L2L2 mL

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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 1.9

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The total volume of seawater is 1.5 x 10 21 L. Assume that seawater contains 3.1 percent sodium chloride by mass and that its density is 1.03 g/mL. Calculate the total mass of sodium chloride in “English” tons (1 ton = 2000 lbs, 1 lb = 453.6 g). What information are we given? Density of seawater Volume of seawater Proportion of salt in seawater by mass d = 1.03 g (of seawater) mL (of seawater) V = 1.5 x 10 21 L (of seawater) 3.5 g (of salt) 1000 g (of seawater) What do we want to know? Mass of salt in seawaterm = ??? tons (of salt)

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The total volume of seawater is 1.5 x 10 21 L. Assume that seawater contains 3.1 percent sodium chloride by mass and that its density is 1.03 g/mL. Calculate the total mass of sodium chloride in (English) tons. What conversion factors will we need? What formulas/principles connect what we are given to what we want to know? 1 L = 1000 mLliters milliliters grams tons 453.6 g = 1 lb 2000 lb = 1 ton definition of density connects mass, volume, and density (of seawater in this case) % by mass connects mass of seawater to mass of salt

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convert gram s.w. to grams salt The total volume of seawater is 1.5 x 10 21 L. Assume that seawater contains 3.1 percent sodium chloride by mass and that its density is 1.03 g/mL. Calculate the total mass of sodium chloride in (English) tons. Put together the calculation (dimensional analysis). d = V m m = V x d 1.5 x 10 21 L s.w. x 3.1 g salt 1000 g s.w. 1.03 g s.w. 1 mL s.w x 1000 mL 1 L x 1 lb 453.6 g x 1 ton 2000 lbs x = 5.3 x 10 16 tons salt unit mismatch! m = convert grams to lbs convert lbs to tons

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