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Chapter 1: Introduction Classification of Matter Matter can exist in different forms or phases: (1) States of Matter Chapter 1: Introduction Classification of Matter Chapter 1: Introduction Classification of Matter Defined Defined Distance Compressible? shape? volume? between molecules? Solid Liquid Gas Chapter 1: Introduction Classification of Matter (2) Molecules, Elements, Compounds, Pure Substances, and Mixtures Molecules: atom Chapter 1: Introduction Classification of Matter (2) Molecules, Elements, Compounds, Pure Substances, and Mixtures Elements: Chapter 1: Introduction Classification of Matter (2) Molecules, Elements, Compounds, Pure Substances, and Mixtures Compounds: Chapter 1: Introduction Classification of Matter (2) Molecules, Elements, Compounds, Pure Substances, and Mixtures Pure Substance: Chapter 1: Introduction Classification of Matter (2) Molecules, Elements, Compounds, Pure Substances, and Mixtures Mixtures: Chapter 1: Introduction Classification of Matter (2) Molecules, Elements, Compounds, Pure Substances, and Mixtures Homogeneous Mixtures <-> Heterogeneous Mixtures Oil on water Air HW: 1, 2 Chapter 1: Introduction Classification of Matter (2) Molecules, Elements, Compounds, Pure Substances, and Mixtures Phase state? Molecules or atoms? Compound? Mixture? - what kind? HW: 9, 15 Chapter 1: Introduction Homogenous or Heterogeneous Mixtures? Vinaigrette Mud Granite Coffee - a Coffee - b Brass Water and flour Chapter 1: Introduction Chapter 1: Introduction Mixtures can be separated ... for example by Filtration Chromatography Distillation Chapter 1: Introduction Properties of Matter Physical Properties & Changes → no change in identity or composition of substance Chemical Properties & Changes → how a substance reacts to form a different substance HW: 17, 19 Chapter 1: Introduction Properties of Matter Burning of wood: Melting of ice: Chapter 1: Introduction Physical of Chemical Property? Zinc (Zn): ● silver-grey metal ● melting point: 420oC ●reacts with oxygen to form Zinc oxide (ZnO) ● density (25oC) = 7.13 g/cm3 ●generates hydrogen when dissolved in sulfuric acid Chapter 1: Introduction Physical or Chemical Process? Sugar dissolving in water. The picture on the left represents a) compounds in the gas phase b) elements in the gas phase c) molecules in the gas phase d) a heterogeneous mixture of elements e) a mixture of molecules in the liquid phase Chapter 1: Introduction Intensive Properties… …are independent of the amount of substance Extensive Properties… …depend on the amount of substance Boiling/melting point (bp/mp) Mass Volume Density Chapter 1: Introduction A gold nugget (1cm x 0.5 cm x 0.7 cm) has a density of 19.3 g/cm3. A jeweler decides to use this gold nugget to make a perfect gold Sphere with a diameter of 0.4cm. What is the density of this sphere? Chapter 1: Introduction Units of Measurement: Temperature K = OC + 273 Chapter 1: Introduction Units of Measurement Système International d'Unités (SI units) Mass kilogram kg Length meter m Time second s Temperature Kelvin K Amount of a substance mole mol Chapter 1: Introduction Units of Measurement Prefixes used in the metric system: You ABSOLUTELY MUST know these (Table 1.5 page 14): Giga G gigameter (Gm) = 109 m Mega M megameter (Mm) = 106 m Kilo K kilometer (Km) = 103 m meter (m) =1m Deci d decimeter (dm) = 10-1 m Centi c centimeter (cm) = 10-2 m Milli m millimeter (mm) = 10-3 m Micro µ micrometer (µm) = 10-6 m Nano n nanometer (nm) = 10-9 m Pico p picometer (pm) = 10-12m Femto f femtometer (fm) = 10-15m Chapter 1: Introduction Units of Measurement: Derived Units Volume: 1m (1 m)3 = 1m3 = 1cubic meter 1m 1m 1cm (1 cm)3 = 1cm3 = 1cubic centimeter = 1mL 1cm 1cm HW: 24, 29 Chapter 1: Introduction Units of Measurement: Derived Units mass Density = volume ● Generally expressed as g/mL or g/cm3 ● Depend on temperature HW: 49, 52 Chapter 1: Introduction Dimensional Analysis Converting inches into cm: Conversion factor: same quantity but in different units 2.54cm 23.2in 58.9cm 1in - the units to be eliminated go on opposite sides of the fraction Converting m/min into m/s: m 1 min m 1.2 × = 0.020 min 60 s s Conversion factor Chapter 1: Introduction Dimensional Analysis More than one conversion: A car travels 12 km per liter of gasoline. How many many miles per gallon will it go? => Convert 12 km/L into mi/gallon => first, convert length units: km into mi, second, convert volume units: L into gallons 1 mi km 1.61 km (1) 12 × or L 1.61 km 1 mi Chapter 1: Introduction Dimensional Analysis More than one conversion: A car travels 12 km per liter of gasoline. How many many miles per gallon will it go? => Convert 12 km/L into mi/gallon => first, convert length units: km into mi, second, convert volume units: L into gallons km 1 mi mi (1) 12 × = 7.45 L 1.61 km L 1 gal mi 3.785 L (2) 7.45 × or L 3.785 L 1 gal Chapter 1: Introduction Dimensional Analysis More than one conversion: A car travels 12 km per liter of gasoline. How many many miles per gallon will it go? => Convert 12 km/L into mi/gallon => first, convert length units: km into mi, second, convert volume units: L into gallons km 1 mi mi (1) 12 × = 7.45 L 1.61 km L mi 3.785 L mi mi Correct number (2) 7.45 × = 28.198 = 28 of sig. figs. L 1 gal gal gal Chapter 1: Introduction Dimensional Analysis More than one conversion: A car travels 12 km per liter of gasoline. How many many miles per gallon will it go? => Convert 12 km/L into mi/gallon => first, convert length units: km into mi, second, convert volume units: L into gallons => with more PRACTICE you can combine steps (1) and (2): km 1 mi 3.785 L mi 12 × × = 28 L 1.61 km 1 gal gal Chapter 1: Introduction Dimensional Analysis Conversions involving squared and cubic units: The volume of a container is 5.3 m3. What is the volume in cm3? => Convert m3 into cm3 100 cm 5.3 m3 × 1m Units must match in order to cancel out! Chapter 1: Introduction Dimensional Analysis Conversions involving squared and cubic units: The volume of a container is 5.3 m3. What is the volume in cm3? => Convert m3 into cm3 3 1003 cm3 5.3 m × = 53,00000 cm3 13 m3 = 5.3 × 1000000 cm3 = 5.3 × 106 cm3 Units must match = cube both number AND unit ! HW: 35 Chapter 1: Introduction Uncertainty in Measurement Inexact Numbers Obtained by measurement Exact Numbers Value is known precisely The temperature of the asphalt Mass of 1L of milk? The number of mm in on Randall Drive today? one yd of speaker cable ? Chapter 1: Introduction Uncertainty in Measurement good accuracy poor accuracy poor accuracy good accuracy good precision good precision poor precision poor precision Accuracy: how do the measured values agree with the “true” value? Precision: how reproducible is the measurement? Chapter 1: Introduction Significant Figures Which digits count? (a) All significant digits in a number Zeros... (b) ...between nonzero digits count (c) ...in the beginning of a number never count (d) ...in the end of a number count (compare lab manual) 0.04305 4 sig figs 0.34000 5 sig figs 1.04305 6 sig figs 45,000 2 sig figs Chapter 1: Introduction Significant Figures 0.04305 4 sig figs 0.34000 5 sig figs 1.04305 6 sig figs 45,000 2 sig figs This is easiest to see when written in exponential notation: 0.04305 = 4.305 x 0.01 = 4.305 x 10-2 0.34000 = 3.4000 x 0.1 = 3.4000 x 10-1 45,000 = 4.5 x 10000 = 4.5 x 104 Chapter 1: Introduction Significant Figures ● Final result is only as accurate as the least accurate measurement ● The least accurate measurement determines the number of sig. figs. (1) Division and Multiplication: volume = 1.32cm x 1.1cm x 3.540cm = 5.14008cm3 = 5.1cm3 Answer rounded to 2 sig. figs. velocity = 342 m / 32 s = 10.6875 m/s = 11 m/s Answer rounded to 2 sig. figs. Number with fewest sig. figs. determines sig. figs. of answer Chapter 1: Introduction Significant Figures ● Final result is only as accurate as the least accurate measurement ● The least accurate measurement determines the number of sig. figs. (2) Addition and Subtraction 1.234 Number with fewest decimal places + 0.124 (NOT sig. Figs.) determines answer + 320.13 - 56.1 = 265.388 = 265.4 answer rounded to 1 decimal point

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