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Large scale world in terms of microscopic atomic

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Unformatted text preview: hemists try to understand and explain the macroscopic (large scale) world in terms of microscopic (atomic, molecular scale) composition and reactions. • Chemists have devised a number of different ways of representing atoms and molecules. • To understand chemistry, you must be able to read and write these models of the molecular world. Table 1.1: Chemical Models Chemical Model Molecular formula Structural formula Hydrogen Oxygen Water H2 H-H O2 O=O H2 O H-O-H Ball & stick model Space filling model In molecular formulas, the subscript tells number of atoms to the left of it. If there isn’t a subscript, it means that there is one atom. For example, water has two atoms of H and one atom of O. 7 Copyright © 2007 by Concise Books Publishing LLC. Visit us at www.concisechem.com to download other free chapters from "The Concise Guide to Chemistry." CHAPTER 1.2.4 1: INTRODUCTION TO CHEMISTRY Scientific Method Scientific method provides guidance for the practice of science. The scientific method is summarized by the sequence of steps in Figure 1.1. • After observing a number of facts, either through the pursuit of one’s own research interests or by simply learning about findings of others, a scientist forms a general idea to correlate the observed facts. This idea is called a hypothesis (tentative explanation of observed data). • The hypothesis has to be subjected to further test though experiments. If experiments fail to confirm the hypothesis, the scientist must revise to hypothesis to reflect the new data. If the experiments confirm the hypothesis, other scientists perform the experiments as well to confirm the findings. • These successful findings are usually combined in a scientific law (law), which summarizes the observed experimental facts. For example, Charles’s Law states that the volume (V) of a gas directly with an in temperature (T). Note that a law makes no attempt to explain “why” that happens. • An explanation of the relationship between T & V is given by the kinetic theory of gases, which not only explains the observations, but also correctly predicts many other properties of gases. Hypothesis is a tentative explanation. Laws are tested generalizations. Theory is a verified hypothesis compounded of facts, laws and deductive arguments (inferences). The paradox of science is that every answer to a question results into new questions. The more we learn, the more we realize how little we know. What this means is that some of the biggest questions still remain to be asked in our never ending quest for understanding “everything.” 8 Copyright © 2007 by Concise Books Publishing LLC. Visit us at www.concisechem.com to download other free chapters from "The Concise Guide to Chemistry." CHAPTER 1: INTRODUCTION TO CHEMISTRY Figure 1.1: Scientific Method QUESTIONS & DESIRE FOR TRUTH DATA FROM OBSERVATIONS & EXPERIMENTS Experiments fail to confirm the hypothesis. New hypothesis is formed based on...
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