Chemistry at Karlsruhe 1860: Using Reacting to the Past in

General Chemistry

David E. HendersonTrinity College

Susan K HendersonQuinnipiac University

Philosophies of Science

• Plato –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 observations– atoms must be considered to be real to fully describe how different

arrangements of the same atoms can produce different properties.

Learning Goals – Karlsruhe Game• History of the study of matter and its behavior

referred to as “chemistry”• Evidence as the basis of chemical knowledge• The process of science• Development of quantitative skills

Karlsruhe Conference

• First International Scientific Meeting– held in Karlsruhe, Germany, October 1860

• Topics to be considered – Are Atoms Real?– What is the proper formula for water? HO, H2O– Can we assign atomic weights to elements or only

equivalent weights?• Is Carbon 6 or 12? Oxygen 8 or 16?

• Each element is made up of tiny particles called atoms.

Dalton’s Atomic Theory (1808)

• The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.

Dalton’s Atomic Theory (continued)

• Chemical 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.

Dalton’s Atomic Theory (continued)

• Chemical reactions involve reorganization of the atoms—changes in the way they are bound together.

• The atoms themselves are not changed in a chemical reaction.

Dalton’s Atomic Theory (continued)

Law of conservation of mass – Mass is neither created nor destroyed

Law 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 Dalton’s Theory

Karlsruhe Conference

• Factions– Berzelian Empiricists (Bunsen, Frankland)– Liebig Empiricists (Liebig, Meyer)– Organic Realists (Williamson, Kekule)– Cannazzaro– Indeterminates (Pasteur, Mendeleev)

Berzelians

• Prof 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 H

Berzelians

• They reject anything that is not based on observation and measurement, ie empirical data

• They believe that matter is composed of electropositive and electronegative atoms

Example of empirical data

• Data for the Law of multiple proportions– 1 g oxygen reacts with 0.4375 g nitrogen– 1 g oxygen reacts with 0.8750 g nitrogen– 1 g oxygen reacts with 1.750 g nitrogen– Suggests 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 oxygen• 0.8750/0.4375= 2• 1.750/0.4375= 4• NO, NO2, NO4 or NO1/2, NO, NO2 can’t tell which from this data

Liebig• Prof. Justus Liebig and his group developed methods to

analyze organic chemical• Like the Berzelians they dealt only with empirical data and

equivalent weights• Organic Compounds generally are made up of carbon,

hydrogen and oxygen• Organic compounds when combusted in air form water, and

carbon dioxide• Liebig determined the simplest formulas (empirical formulas)

of any compound of C, H and O which includes sugars, alcohols, and many others.

• Liebig’s apparatus is still honored in the Am Chem Soc Logo

• Gay—Lussac Measured (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 HO

Basic conflict between volume and mass measurements!

Gay-Lussac and Avogadro (1809—1811)

• Avogadro’s Hypothesis At the same T and P, equal volumes of

different gases contain the same number of particles.

EVEN Hypothesis – Widely Accepted

Gay-Lussac and Avogadro (1809—1811)

The EVEN Hypothesis

• Equal 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 Chemistry

• Discovery of isomers– Same molecule but assembled differently• Butyl Alcohol and ether both same formula but

different properties• Butyric acid and hydroxyethylene both C2H2O according

to Liebig– One an acidic liquid and one a volatile alcohol

– Idea of chemical structure related to properties• If arrangement of atoms is important, they

must be real

Organic Realists

• Many 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

Canizzaro

• Stanisllao Canizzaro, Prof of Chemistry in Genoa, Italy

• Not well known

Indeterminates

• Every RTTP Game has indeterminates• They are assigned roles and may have secrets

but they have no predetermined opinions about the issues being debated

• In 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 convinced

Things All Factions Believe are True• EVEN – Equal Volumes contain Equal Numbers– Hypothesis allows determination of relative

weights of different compounds• Law of Multiple Proportions– Compounds contain fixed ratios of elements– Some elements combine in multiple ratios

Things All Factions Don’t Know• The Mole Concept• Atomic Weights (Relative and Equivalent only)• The Periodic Table• Diatomic Nature of Elemental Gases, O2, H2

• Whether Atoms are Real or just a useful idea• Relative weights of Carbon and Oxygen• Formulas of water and carbon oxides• Concept of Covalent Bonding

Data for the Debate• Experimental data to be presented– Combination of Metals with oxygen (oxidation)– Combination of Metals with hydrogen (reduction)– Electrolysis (decomposition)– Combustion (burn organic molecule to decompose

into Carbon, Hydrogen and Oxygen– Gas Density measurements allowed the relative

weights of atoms and molecules to be determined

Game Session 1

• Factions describe experiments• Factions present calculated results and

conclusions from the data• Each faction makes different assumptions – Assumptions are based on empirical evidence

• Answer keys for are provided for this workshop

Game Session 2

• Examine the other groups data using your assumptions

• Look for consistent results• Make arguments for your faction’s objectives