PowerPoint Presentation

Chemistry at Karlsruhe 1860: Using Reacting to the Past in General ChemistryDavid E. HendersonTrinity CollegeSusan K HendersonQuinnipiac University

1Philosophies of SciencePlato describe nature by thinking about the ideal state rather then the real state (logic)Aristotle observe nature and then try to describe its properties and behavior Empiricists develop laws and relationships to describe nature only by direct observations/measurements. Not concerned with underlying causes.Realists Understanding underlying causes is necessary to fully explain observationsatoms must be considered to be real to fully describe how different arrangements of the same atoms can produce different properties.

Learning Goals Karlsruhe GameHistory of the study of matter and its behavior referred to as chemistryEvidence as the basis of chemical knowledgeThe process of scienceDevelopment of quantitative skills

3Karlsruhe ConferenceFirst International Scientific Meeting held in Karlsruhe, Germany, October 1860Topics to be considered Are Atoms Real?What is the proper formula for water? HO, H2OCan we assign atomic weights to elements or only equivalent weights?Is Carbon 6 or 12? Oxygen 8 or 16?

4Each element is made up of tiny particles called atoms.Daltons Atomic Theory (1808)

5The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.Daltons Atomic Theory (continued)6Chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers and types of atoms.Daltons Atomic Theory (continued)7Chemical reactions involve reorganization of the atomschanges in the way they are bound together. The atoms themselves are not changed in a chemical reaction.Daltons Atomic Theory (continued)8Law of conservation of mass Mass is neither created nor destroyedLaw of definite proportion A given compound always contains exactly the same proportion of elements by mass.Law of multiple proportions If two elements can combine to form more than one compound, the masses of one element that combines with a fixed mass of the other element are in ratios of small whole numbers CuO and Cu2O Fe 2O3 and FeO

Laws from Daltons Theory9Karlsruhe ConferenceFactionsBerzelian Empiricists (Bunsen, Frankland)Liebig Empiricists (Liebig, Meyer)Organic Realists (Williamson, Kekule)CannazzaroIndeterminates (Pasteur, Mendeleev)

10BerzeliansProf Berzelius was one of the leading chemists at that time.Berzelius performed over 2000 different experimentsThis group assigned relative weights of 1 for H, 6 for C and 16 for O. Meaning that C is 6 times as heavy as H, O is 16 times as heavy as HBerzeliansThey reject anything that is not based on observation and measurement, ie empirical dataThey believe that matter is composed of electropositive and electronegative atomsExample of empirical dataData for the Law of multiple proportions1 g oxygen reacts with 0.4375 g nitrogen1 g oxygen reacts with 0.8750 g nitrogen1 g oxygen reacts with 1.750 g nitrogenSuggests that oxygen reacts with nitrogen to give three different compounds. Look at the ratios of the mass of nitrogen that reacts with 1 gram of oxygen0.8750/0.4375= 21.750/0.4375= 4NO, NO2, NO4 or NO1/2, NO, NO2 cant tell which from this dataLiebigProf. Justus Liebig and his group developed methods to analyze organic chemicalLike the Berzelians they dealt only with empirical data and equivalent weightsOrganic Compounds generally are made up of carbon, hydrogen and oxygenOrganic compounds when combusted in air form water, and carbon dioxideLiebig determined the simplest formulas (empirical formulas) of any compound of C, H and O which includes sugars, alcohols, and many others.Liebigs apparatus is still honored in the Am Chem Soc Logo

GayLussacMeasured (under same conditions of T and P) the volumes of gases that reacted with each other. For Example for water H2O

But 1 g H combines with 8 g O 9 g water suggesting HOBasic conflict between volume and mass measurements!Gay-Lussac and Avogadro (18091811)

15Avogadros HypothesisAt the same T and P, equal volumes of different gases contain the same number of particles.EVEN Hypothesis Widely AcceptedGay-Lussac and Avogadro (18091811)16The EVEN HypothesisEqual Volumes have even numbers All gases are observed to follow this rule

Implication is that all atoms must be the same size since a filled container of different gases weigh different amounts

Therefore - Some atoms are heavier than others

Rise of Organic ChemistryDiscovery of isomersSame molecule but assembled differentlyButyl Alcohol and ether both same formula but different propertiesButyric acid and hydroxyethylene both C2H2O according to LiebigOne an acidic liquid and one a volatile alcoholIdea of chemical structure related to propertiesIf arrangement of atoms is important, they must be real18Organic RealistsMany different organic compounds can have the same empirical formula but are very different, sugars are denoted as CH2O but glucose (blood sugar) and sucrose (table sugar) are two different substances.The EVEN hypothesis is used to determine relative weights of organic compounds

19CanizzaroStanisllao Canizzaro, Prof of Chemistry in Genoa, ItalyNot well known

IndeterminatesEvery RTTP Game has indeterminatesThey are assigned roles and may have secrets but they have no predetermined opinions about the issues being debatedIn this game they will act as moderators of the game sessions.Their votes are critical to the outcome, so they are the ones to be convincedThings All Factions Believe are TrueEVEN Equal Volumes contain Equal NumbersHypothesis allows determination of relative weights of different compoundsLaw of Multiple ProportionsCompounds contain fixed ratios of elementsSome elements combine in multiple ratios

22Things All Factions Dont KnowThe Mole ConceptAtomic Weights (Relative and Equivalent only)The Periodic TableDiatomic Nature of Elemental Gases, O2, H2Whether Atoms are Real or just a useful ideaRelative weights of Carbon and OxygenFormulas of water and carbon oxidesConcept of Covalent Bonding

23Data for the DebateExperimental data to be presentedCombination of Metals with oxygen (oxidation)Combination of Metals with hydrogen (reduction)Electrolysis (decomposition)Combustion (burn organic molecule to decompose into Carbon, Hydrogen and OxygenGas Density measurements allowed the relative weights of atoms and molecules to be determined

24Game Session 1Factions describe experimentsFactions present calculated results and conclusions from the dataEach faction makes different assumptions Assumptions are based on empirical evidenceAnswer keys for are provided for this workshop

25Game Session 2Examine the other groups data using your assumptionsLook for consistent resultsMake arguments for your factions objectives

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