Chapter 1: Chemistry and the Atomic/Molecular View of Matter Chemistry: The Molecular Nature of Matter, 6E Brady/Jespersen/Hyslop

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 1.2- Scientific Method  Approach to gathering information & formulating explanations.  Scientists perform experiments in laboratories under controlled conditions 1.Make observations/collect data 2.Law or Scientific Law 3.Hypothesis 4. Theory 2

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Atomic Theory  Most significant theoretical model of nature Atoms  Tiny submicroscopic particles  Make up all chemical substances  Make up everything in Macroscopic world  Smallest particle that has all properties of given element  Composed of:  Electrons  Neutrons  Protons 3

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 1.3- Matter & Its Classifications Matter  Anything that has mass & occupies space Mass  How much matter given object has Weight  Force with which object is attracted by gravity Ex. Mass vs. Weight Astronaut on moon & on earth  Weight on moon = 1 / 6 weight on earth  Same mass regardless of location 4

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Matter Chemical Reactions  Transformations that alter chemical compositions of substances Decomposition  Chemical reaction where 1 substance broken down into 2 or more simpler substances Ex. 5 Molten sodium chloride Sodium metal Na + chlorine gas Cl 2 Electric current

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Elements  Substances that can’t be decomposed into simpler materials by chemical reactions  Substances composed of only 1 type of atom H 2, O 2, Cl 2, Br 2, Na, Ca, Fe  More complex substances composed of elements in various combinations 6 diamond = carbongoldsulfur

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Chemical Symbols for Elements Chemical Symbol  One or two letter symbol for each element name  First letter capitalized, second letter lower case Ex. C = carbonS = sulfur Ca = calciumAr = argon Br = bromineH = hydrogen Cl = chlorineO = oxygen  Used to represent elements in chemical formulas Ex. Water = H 2 O Carbon dioxide = CO 2  Most based on English name  Some based on Latin or German names 7

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Chemical Symbols English NameChemical SymbolLatin Name SodiumNaNatrium Potassium KKalium IronFeFerrum CopperCuCuprum SilverAgArgentum GoldAuAurum MercuryHgHydrargyrum AntimonySbStibium TinSnStannium LeadPbPlumbum TungstenWWolfram (German) 8

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Compound  Formed from 2 or more atoms of different elements  Always combined in same fixed ratios by mass  Can be broken down into elements by some chemical changes Ex. Water decomposed to elemental hydrogen & oxygen Mass of oxygen = 8 × mass of hydrogen 9

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Pure Substance vs. Mixture Pure substances  Elements and compounds / H 2 O, Na, N 2, …  Composition always same regardless of source Mixture  Can have variable compositions  Made up of two or more substances Ex. CO 2 in water—varying amounts of “fizz” in soda  2 broad categories of mixtures:  Heterogeneous Mixtures  Homogeneous Mixtures 10

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Homogeneous Mixtures  Same properties throughout sample  Solution  Thoroughly stirred homogeneous mixture Ex.  Liquid solution  Sugar in water  Salt in water  Gas solution  Air  Contains nitrogen, oxygen, carbon dioxide & other gases  Solid solution  US 5¢ coin – Metal Alloy  Contains copper & nickel metals 11 Other examples -Flour -Milk powder -Potable water -Gasoline

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Heterogeneous Mixtures  2 or more regions of different properties  Solution with multiple phases  Separate layers Ex.  Salad dressing  Oil & vinegar  Ice & water  Same composition  2 different physical states  Ether and water  Soil 12

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Physical Change  No new substances formed  Substance may change state or the proportions Ex. Ice melting or water freezing  Sugar or salt dissolving  Melting of metals  Condensation of vapor or evaporation of water  Stirring iron filings & sulfur together 13

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Chemical Change or Chemical Reaction  Formation of new substance or compound  Involves changing chemical makeup of substances  New substance has different physical properties  Can’t be separated by physical means Ex.  Fool’s gold  Compound containing sulfur & iron  No longer has same physical properties of free elements  Can’t be separated using magnet 14

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Learning Check: ChemicalPhysical Magnesium burns when heated Magnesium metal tarnishes in air Magnesium metal melts at 922 K Grape Kool-aid lightens when water is added 15  For each of the following, determine if it represents a Chemical or Physical Change: X X X X

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Classification of Matter 16

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Learning Check: Classification Hot Cocoa Ice (H 2 O) White Flour Table Salt (NaCl) Pure substance Element Compound Molecule Heterogeneous Mixture Homogeneous Mixture 17 X X X XX X X

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 1.5- Atoms and Molecules Chemical Formulas  Atoms combine to form more complex substances  Discrete particles  Each composed of 2 or more atoms Ex.  Molecular oxygen, O 2  Carbon dioxide, CO 2  Ammonia, NH 3  Sucrose, C 12 H 22 O 11 18

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Chemical Formulas  Specify composition of substance  Chemical symbols  Represent atoms of elements present  Subscripts  Given after chemical symbol  Represents relative numbers of each type of atom Ex. Fe 2 O 3 : iron & oxygen in 2:3 ratio 19

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Chemical Formulas Free Elements  Element not combined with another in compounds  Just use chemical symbol to represent Ex. Iron FeNeonNe SodiumNaAluminumAl Diatomic Molecule  Molecules composed of 2 atoms each  Many elements found in nature Ex. OxygenO 2 NitrogenN 2 HydrogenH 2 ChlorineCl 2 20

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Depicting Molecules  Want to show:  Order in which atoms are attached to each other  3-dimensional shape of molecule  Three ways of visualizing molecules: 1. Structural formula 2. Ball-and-Stick model 3. Space filling model 21

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 1. Structural Formulas  Use to show how atoms are attached  Atoms represented by chemical symbols  Chemical bonds attaching atoms indicated by lines 22 H 2 O water CH 4 methane

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 3-D Representations of Molecules  Use touching spheres to indicate molecules  Different colors indicate different elements  Relative size of spheres reflects differing sizes of atoms 23 Hydrogen molecule, H 2 Oxygen molecule, O 2 Nitrogen molecule N 2 Chlorine molecule, Cl 2

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 2. “Ball-and-Stick” Model  Spheres = atoms  Sticks = bonds 24 Chloroform, CHCl 3 Methane, CH 4

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 3. “Space-Filling” Model  Shows relative sizes of atoms  Shows how atoms take up space in molecule 25 Chloroform, CHCl 3 Methane CH 4 Water H 2 O

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E More Complicated Molecules  Sometimes formulas contain parentheses  How do we translate into a structure? Ex. Urea, CO(NH 2 ) 2  Expands to CON 2 H 4  Atoms in parentheses appear twice 26 Ball-and-stick model Space-filling model

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Hydrates  Crystals that contain water molecules Ex. plaster: CaSO 4 ∙2H 2 O calcium sulfate dihydrate  Water is not tightly held  Dehydration  Removal of water by heating  Remaining solid is anhydrous (without water) 27 Blue = CuSO 4 5H 2 O White = CuSO 4

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Counting Atoms 1.Subscript following chemical symbol indicates how many of that element are part of the formula  No subscript implies a subscript of 1. 2.Quantity in parentheses is repeated a number of times equal to the subscript that follows. 3.Raised dot in formula indicates that the substance is a hydrate  Number preceding H 2 O specifies how many water molecules are present. 28

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Counting Atoms Ex. 1 (CH 3 ) 3 COH  Subscript 3 means 3 CH 3 groups So from(CH 3 ) 3, we get 3 × 1C = 3C 3 × 3H = 9H #C = 3C + 1C = 4 C #H = 9H + 1H = 10 H #O = 1 O Total # of atoms = 15 atoms 29

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Counting Atoms Ex. 2 CoCl 2 · 6H 2 O  The dot 6H 2 O means you multiple both H 2 & O by 6  So there are: #H6 × 2 = 12 H #O6 × 1 = 6 O #Co1 × 1 = 1 Co #Cl2 × 1 = 2 Cl Total # of atoms = 21 atoms 30

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Your Turn! a.Na 2 CO 3 b.(NH 4 ) 2 SO 4 c.Mg 3 (PO 4 ) 2 d.CuSO 4 ∙5H 2 O e.(C 2 H 5 ) 2 N 2 H 2 31 a.___Na, ___ C, ___ O b.___N, ___H, ___S, ___O c.___Mg, ___P, ___O d.___Cu, ___S, ___O, ___H e.___C, ___H, ___N Count the number of each type of atom in the chemical formula given below

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 1.6- Chemical Reactions  When 1 or more substances react to form 1 or more new substances Ex. Reaction of methane, CH 4, with oxygen, O 2, to form carbon dioxide, CO 2, & water, H 2 O. Reactants = CH 4 & O 2 Products = CO 2 & H 2 O 32

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Chemical Equations  Use chemical symbols & formulas to represent reactants & products.  Reactants on left hand side  Products on right hand side  Arrow (  ) means “reacts to yield” Ex. CH 4 + 2O 2  CO 2 + 2H 2 O  Coefficients  Numbers in front of formulas  Indicate how many of each type of molecule reacted or formed  Equation reads “methane & oxygen react to yield carbon dioxide & water” 33

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Conservation of Mass in Reactions  Mass can neither be created nor destroyed  This means that there are the same number of each type of atom in reactants & in products of reaction  If # of atoms same, then mass also same 34 CH 4 + 2O 2  CO 2 + 2H 2 O 4 H + 4O + C = 4 H + 4O + C

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Balanced Chemical Equation Ex. 2C 4 H O 2  8CO H 2 O 35 4 C & 10 H per molecule 2 O per molecule 2 H & 1 O per molecule 1 C & 2 O per molecule

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Balanced Chemical Equation Ex. 2C 4 H O 2  8CO H 2 O 36 2 molecules of C 4 H molecules of O 2 10 molecules of C 4 H 10 8 molecules of CO 2 Coefficients  Number in front of formulas  Indicate number of molecules of each type  Adjusted so # of each type of atom is same on both sides of arrow  Can change

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Balanced Chemical Equations  How do you determine if an equation is balanced?  Count atoms  Same number of each type on both sides of equation?  If yes, then balanced  If no, then unbalanced Ex. 2C 4 H O 2  8CO H 2 O ReactantsProducts 2×4 = 8 C8×1 = 8 C 2×10 = 20 H10×2 = 20 H 13×2 = 26 O (8×2)+(10×1)= 26 O 37

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Learning Check Fe(OH) HNO 3  Fe(NO 3 ) H 2 O  Not Balanced  Only Fe has same number of atoms on either side of arrow. 38 ReactantsProducts Fe (2×3) = 9 (3×3) + 2 = 11 O = 5(2×2) = 4 H 23 N

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E Your Turn! How many atoms of each element appear on each side of the arrow in the following equation? 4NH 3 + 3O 2 → 2N 2 + 6H 2 O 39 ReactantsProducts N(4 × 1) = 4(2 × 2) = 4 O(3 × 2) = 6(6 × 1) = 6 H(4 × 3) = 12(6 × 2) = 12

Brady/Jespersen/Hyslop Chemistry: The Molecular Nature of Matter, 6E 40 * All Review Questions are required Focus On the following