GECH119 A Brief History of Chemistry

1. GECH119A Brief History of Chemistry Dr. Ralph C. Gatrone Virginia State University Department of Chemistry and Physics

2. Chapter Objectives • Introduce Origins of Universe • Introduce History of Chemistry

3. Assignment • Read the Introduction and Chapter 1 in Investigating Chemistry: A Forensic Science Perspective • For future tests and quizzes you should be able to do problems: 1 – 16 in Chapter 1.

4. Origins: Description of Creation • Based upon scientific observation • Incomplete • Imperfect • Unwitnessed • Most accurate account available • Testable • Reproducible • Supportable

5. Observations • Universe is large • Universe is expanding • Physics allows us to work backwards • Measurement • Quantification • Define underlying relationships • Universe must have been smaller • Underlying relationships can be defined • Big Bang

6. Measurement and Quantification • Agree upon standard units of measurement • International System of Units (SI Units) • Base Units • Mass – kilogram • Length – meter • Time – second • Temperature - Kelvin • Derived Units • Volume, density, speed, force, energy

7. The Big Bang • Universe was small and very hot • Matter/Energy were interconverting • Matter – mass and volume • Energy – capacity to do work • Relationship: E = mc2 • Universe began cooling and expanding • Energy predominated over matter • Amount of matter began increasing

8. How can we say this? • The Big Bang Theory • Incorporates present data • Incorporates present observations • Predicts results of future experiments • If new observation agrees with Theory • Basic concept is supported • Progress continues • If new observation does not agree • Theory must be modified or replaced

9. Direct and Indirect Data • Direct data – • First hand observation • Indirect data • Infer event from clues left behind • Development of models

10. Big Bang Model • Theory developed from indirect data • Model explains this data • Model predicts future experiments and observations

11. Formation of the Elements • Universe cooled after Big Bang • Electrons attached themselves to H and He • Gravity caused matter to collect in clumps • As clumps increased in size electrons were driven off the atoms – plasma formation • Nuclear fusion began – star formation • H atoms fuse to form He + energy released • Galaxies formed

12. Formation of the Elements • H fuses to become He • As H fuel is used He fuses to form Li or Be • Be + He gave C • As atoms get larger energy is required to continue fusion • Fusion stops at formation of Fe • Depending upon size of star • Slowly cool and dim • Gravity pulls all material inward • Implosion followed by explosion • Supernova • Heavy elements formed by this process • Some are radioactive and form other elements through radioactive decay

13. What is Chemistry? • Chemistry is defined as the study of matter and its properties. • When did we begin doing chemistry? • When did we begin doing science?

14. The Beginning • Prehistory - 2,000,000 to 5000 years ago • Paleolithic • Defined by crude stone tools • Neolithic - 12,000 years ago • Defined by complex stone tools

15. Science and Technology • Separate paths • Little trace of science during prehistory • Use of Technology evident • Tool use • Not purely human • Rooted in biology • Observed in nonhumans • Requires thought • Making tools is essential to human existence

16. Technology • Humans • Only species to make tools used to make tools • Human society requires technology advancement for survival

17. Technological Advances • Control of fire • Provided warmth • Enabled migration into cold climates • Provided light • Enabled activity after dark and in dark places • Provided protection • Enabled cooking – aid to digestion • Hardened tools • Enabled social and cultural development

18. Advances • Grasping hand – evolution • Speech – empowered dramatic social changes with cultural consequences • 40,000 years ago • Neanderthal extinct • Homo sapiens • Produced specialized tools • Began trade • Produced art • Buried their dead

19. Homo sapiens • Nomadic • Technology related to food gathering and processing • No surplus food • No institutions necessary • Labor was divided by gender • Population growth forced food collectors • To become food producers

20. Food Producers • Mastery of a set of technologies • Science? • Practical knowledge is different from understanding a phenomenon • Absence of records suggests science was not pursued • Possessed extensive knowledge of nature • Keen observers • May have categorized observations

21. Records • Recorded moon observations on bone • (engraved mammoth tusk from Ukraine) • 2,000,000 • food collectors • little technology • 200,000 • Same lack of progress by our species • 15,000 years ago • Accelerated pace • Why?

22. Pace Increased • Climate change • Extinction of many large animals • Population increase • Formation of large communities for survival • Farming • Animal domestication

23. Development of Ancillary Skills • Textiles • Storage need • Pottery • Pyrotechnology • Metallurgy (primarily copper) • Fermented beverages

24. The Pace • 4000 BC • Metal use is common • 2000 BC • Bronze developed • 1500 BC • Iron extracted • 900 BC • Preservation of Dead

25. Metals • Metals used by virtually all civilizations • Most metals exist as ores • Found combined with O, S, and halogen • Cu, Au, Ag • Cu – most abundant, found in all early civilizations • Au – very soft, useless for all but jewelry • Ag – rarer and more costly than Au

26. Copper • Became inexpensive • Blue rocks • Produced Cu metal • On heating • Wood fire • Soft for use

27. Bronze • Mixing Cu and Sn - alloy • Harder than Cu • More durable edges • Sharper • Bronze Age – metal used as tools, weapons, and armor • Fe was known, but very rare • Found in meteorite remnants

28. Iron • Fe more firmly bound in ores than Cu or Sn • Wood fire is insufficient to smelt Fe • Hittites discovered well ventilated charcoal fire could smelt Fe • Wrought Iron – (Fe) is brittle • Adding C produced the alloy steel • Armor and weapons were first developed

29. Iron Age • Dorians • Barbaric Greek tribe • Conquered Mycenaean Greeks • Using steel weapons (Fe + C) • Greeks moved into Asia Minor • Known as the Philistines • Finally defeated by steel equipped Israelites under King Saul

30. Egypt • Practical chemical arts – very advanced • Embalming and preservation of dead • Metallurgical expertise • Developed use of pigments • Mineral and plant infusions • Where does the word Chemistry come from? • Kham = Egypt, derived into khemeia (Art of Egypt) • Khumos = plant juice (Greek)

31. The Greek Elements • Nature of the universe • Structure of materials • Philosophers (lover of wisdom) • Studied the “why” • Chemical theory • Thales – first recorded Greek philosopher • “can a substance be changed from one material into another?” • Blue stone – heat became red Cu • “Can any substance be changed into another?” • “Are all substances different aspects of one basic material?”

32. Water - Element • Greek philosophers • There is a basic substance • Water was disputed as that substance • Sky was not a semi-sphere, but a complete sphere • Earth was spherical as well • Vacuum could not exist • Sky contained air (experience) • Air – element of the universe

33. Fire • Element should be something that changed • Fire • Ever shifting • Ever changing • Fieriness made change possible

34. Change • Persians conquer Greece • Rule was harsh • Scientific thought was suppressed • Philosophers moved west • Pythagoras went to Italy • Founded a substantial school • Empedocles, Sicily, eminent scholar • Why was there a single element?

35. Four Elements • Fire, Air, Water, and Earth • Accepted by Aristotle • Combination of Properties • Fire = hot and dry • Air = hot and moist • Water = cold and moist • Earth = cold and dry

36. Where did Aristotle come from? • Socrates • Son of a working class family • Set about establishing rules for an ethical society • An irrefutable truth • Doesn’t work well in chemistry • Nature dictates the rules • Natural philosophy was not a good thing to study

37. Where did Aristotle come from? • Socrates • Rejected experimentation • Rejected proof by analogy • Rejected proof by inductive reasoning • Conclusions reached through mental reflection • Deductive reasoning (Socratic method) • Damaged the development of chemistry • Sentenced to death for corrupting the youth • Left star pupil Plato behind

38. Where did Aristotle come from? • Plato • Son of a wealthy family • Father claimed to be the son of Poseidon • Natural philosophy was worthy of study • Remove atheism and retribution • Natural laws are subject to the authority of divine principles • Metals are referred to as waters • They melt • Materials can be transmuted • Founded the Athens Academy • Philosophical and scientific teaching • Best student was Aristotle

39. Aristotle • Four Elements • Heavenly bodies did not appear to change • Properties must be different • Composed of a fifth element • Ether (glow) • Ether was perfect, eternal, incorruptible • Four earthly elements were very different • These ideas lasted for 2000 years

40. Still Present • Raging of elements for a bad storm • Fifth element (ether) = quinta essentia in (Latin) = quintessence = purest form of something

41. Divisibility of Matter • Stone fragments • Each piece can be made smaller • Still stone • Can this go on endlessly? • Leucippus • Eventually you cannot get smaller • Democritus (student) • Ultimately small particles are “atomos” • Meaning indivisible • Atomism is this doctrine

42. Atoms • Each atom of an element has distinct size and shape • Materials Greeks knew • Mixtures of atoms of the different elements • One substance changes into another • Alter this mixture of atoms • Recall: Greeks did NO experimentation • Conclusions were reached • Arguments from first principles • Atomism was rejected by Aristotle

43. Aristotle • Thoughts pervasive for 2000 years • Epicurus made atomism part of his thought • Titus Lucretius Carus – Roman poet • Didactic poem (teaching poem) • De Rerum Natura (On the Nature of Things) • Wrote of the atomist view • Scraps and bits of quotations remained • Aristotle’s view prevailed

44. Why did Aristotle’s philosophy hold sway for so long? • Thoughts had an intuitive appeal • Tutored the son of Philip of Macedonia • Alexander the Great • Conquered most of the known world • Spread Greek culture and philosophy • China to Spain

45. Greeks • The greatest philosophers • Greek hypotheses • Concerning the nature of matter • Concerning the interactions of matter • No experimentation • Hindered chemical advancement

46. Theory and Practical Arts • Egypt – applied chemistry • Greek – theoretical approach • god Thoth was source of chemical knowledge • Associated with Hermes • Mysticism and science relationship

47. Mysticism and Chemistry • Khemeia associated with religion • Practitioners were feared • Priests – knowledge of the gods • Astrologers – knowledge of the future • Chemists – ability to change substances • Used by individuals to increase power

48. Examples • Seven planets were associated with the seven known elements • Gold, silver, copper, iron, tin, lead, and mercury • Kept chemical changes obscure • Retarded progress • Anyone could pretend to be a practitioner

49. First Practitioners • Bolo of Mendes • Studied changing lead (Pb) into gold (Au) • 4 elements suggested the possibility • Red rock gave Fe • Could Fe give Au? • Need the correct process

50. Transmutation: Pb to Au • More profitable to fake the change • Cu(Zn) alloy – brass • Yellow like Au