History of Chemistry Practical Arts and Crafts (---to 600 B.C.E.) Greek Period (600 to 300 B.C. E.) Alchemy (300 B.C.E. to 1650 C.E.) Phlogiston (1650 to 1790) Modern Chemistry (1790--- ) Note: This listing focuses on the Middle East and Western Europe. Dates are very approximate

Practical Arts and Crafts Variations found in almost all cultures Practical uses of Chemistry in “everyday life” Pottery, baking, brewing, medicines, extracting metals from ores Empirical focus: what works--did not ask why

Greek Period Philosophical approach Attempt to understand principles that would explain the universe Not supported by empirical evidence Not supported by experimental data

Alchemy Combined Greek philosophical tradition with practical Egyptian craft tradition Mixed astrology and mysticism and Greek philosophical tradition with practical knowledge Alexandria (331 BCE) had greatest library of ancient times, including books with diagrams of chemical equipment and processes

Main focus of Alchemists Search for philosopher’s stone (elixir of life) confer immortality transmute base metals into gold Later emphasis on Iatrochemistry (medicinal chemistry)

Spread of Islam after 640 CE brought Arab influence to many areas surrounding the Mediterranean and mid-east These areas were much more advanced than Western Europe (still in the Dark Ages) Centers of Learning in Spain and other areas Never found the philosopher’s stone, but acquired much practical information about chemistry

Phlogiston Era Stahl thought that there was a “fire principle” called phlogiston in anything that would burn Phlogiston would be released when it burned Wood → Ash + Phlogiston (into air)

Wood → Ash + Phlogiston (into air) Ashes weigh less than wood Metals → Calx + Phlogiston Calx often weighed MORE than metals Contradictory information here— Can removing something both lower and raise weight?

Mg + O2 → MgO Now know that oxygen from air reacts with metals such as Mg to form a new compound MgO 2 Mg + O2 → 2 MgO (balanced)

Modern Chemistry Robert Boyle – The Skeptical Chymist 1661 Relied on Expermental Evidence Lots of information developed during the intervening years

Antoine Lavoisier (1743-1794) Carefully weighed materials before and after burning (closed container) Elementary Treatise on Chemistry---1789 Chemistry described in “modern” terms

Law of Conservation of Matter (Mass) Matter cannot be created or destroyed by ordinary chemical means