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CHEM 1100 (7)
Chapter 1


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University of Guelph
CHEM 1100
Kim Bolton

CH.1 MOLECULAR REASONS Molecular Reasons • Molecules are tiny particles that make up matter • Chemistry is the science that investigates the molecular reasons for the processes occurring in our macroscopic world • Societal impact  understanding chemistry deepens our understanding of the world and our understanding of ourselves because all matter, even our own brains and bodies, is made of atoms and molecules • By using the scientific method, chemists investigate the molecular world; they examine the molecular reasons for our macroscopic observations Observation Law Hypothesis Theory Experiment • 1st step in scientific method is observation or measurement of some aspect of nature  May involve one person making visual observations or may require team of scientists working together with complex instrumentation • A series of relates observations/measurements can be combined to formulate a generalization called scientific law  Scientific law summarizes and predicts behaviour but they do not explain the underlying cause • Hypothesis is an attempt to explain the underlying causes of observations and laws • An experiment is a controlled observation specifically designed to test a hypothesis • One or more confirmed hypotheses may evolve into a theory  A good theory often predicts behaviour far beyond the observations and laws from which it was formulated  A theory is valid if it is consistent with or predicts the outcomes of experiments  If an experiment is inconsistent with a theory, that theory must be revised, and a new set of experiments must be performed to test the revision  A theory is never proved but only validated by experimentation The First People to Wonder about Molecular Reasons • 600 B.C. people wondered about the reasons for the world and its behaviour CH.1 MOLECULAR REASONS • Several Greek philosophers believed that reason was the primary way to unravel the mysteries of nature, therefore they did not emphasize observation and experimentation  They made some progress in understanding the natural world and introduced fundamental ideas such as atoms and elements • Thales reasoned that any substance could be converted into any other substance, so that all substances were in reality one basic material  Thales believed the one basic material was water because it the element of things  Empedocles suggested matter was composed of air, water, fire and earth  Aristotle added a 5 element-the heavenly ether-perfect, eternal, and incorruptible Immortality and Endless Riches • Alchemy: a partly empirical, partly magical, and entirely secretive pursuit with 2 main goals: the transmutation of ordinary materials into gold; and the discovery of the elixir of life, a substance that would grant immortality to any who consumed it • It was the predecessor of chemistry and flourished in Europe during the middle ages • Societal impact  through obsession of turning metals into gold they learned about forming alloys( a mixture of metals with unique properties)  Contributed to the development of laboratory separation and purification techniques  Made advances in pharmacology by isolating natural substances and using them to treat ailments The Beginning of Modern Science th • In 16 CE scientists began to focus on observation and experimentation as the key to understanding the natural world • Books written by Copernicus and Vesalius exemplify this change of perspective and marks the beginning of the scientific revolution  Copernicus claimed the Sun was the center of the universe  Vesalius portrayed human anatomy accurately • These books were followed by relatively rapid developments in our understanding of the chemical world • Galileo expanded on Copernicus’s ideas and contradicted the Roman Catholic Church th • In the 17 CE Boyle initiated a scheme that can be used to classify matter according to its composition The Classification of Matter • Matter can be classified by its composition (what it’s composed of) or by its state (solid, liquid, or gas Classification of Matter • A pure substance may either be an element or compound CH.1 MOLECULAR REASONS • Element is a substance that cannot be decomposed into simpler substances • The smallest identifiable unit of an element is an atom • There are about 90 different elements in nature and therefore about 90 different kinds of atoms • A compound is a substance composed of 2 or more elements in fixed, definite proportions • Compounds are more common in nature than elements because most elements tend to combine with other elements to form compounds • The smallest identifiable unit of many compounds is a molecule, two or more atoms bonded together • A mixture is a combination of 2 or more pure substances in variable proportions • Substances in mixtures may either be 2 or more elements/compounds •
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