Chemistry Week 1

Chemistry Week 1 - Chemical Fundamentals Introduction (1)...

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Chemical Fundamentals Introduction (1) Importance of Chemistry in Our Society (a) Many day-to-day activities rely on chemistry (b) World issues need scientific solutions: health, energy, and environment (c) Chemistry is a component of most scientific areas—thus it is a central science (2) Key Aspect -- particulate (atomic/molecular) nature of matter as it relates to real observations (the macroscopic world). (3) Scientific Research – chemistry is an empirical science; it relies on (i) Making hypotheses, (ii) Taking experimental observations (using computation, too!), (iii) Data accumulation and organization, (iv) Checking the scientific literature, (v) Drawing inferences and conclusions (vi) Repeating step (i)… See Beyond the Molecular Frontier , National Research Council, 2003, which lists some grand challenges for chemists and chemical engineers. Two important resources : (1) Handbook of Chemistry and Physics , D.R. Lide, Editor-in-Chief, CRC Press, Boca Raton, FL. This handbook contains a lot of useful information about various chemical substances. It is published annually and there are occasional updates. (2) The Iowa State University library’s website for e-resources in chemistry is another valuable resource for scientific information. Matter TEXTBOOK READING : BLB-10 , Chapter 1, pp. 1-13. Practice PROBLEMS: (Ch. 1) 17-20 (1) Taxonomy Chemists distinguish among different categories of matter based upon composition and properties. Fundamentally, there occur pure substances or mixtures of two or more substances. (a) Pure Substances : Has a definite, constant composition and distinctive properties, e.g., color, density, conductivity, magnetism, smell. Pure substances can be either
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Elements : Cannot be separated into simpler substances by chemical means. 112 elements have been identified; 83 occur naturally on Earth; listed in the periodic table . Compounds : Composed of atoms of two or more elements chemically united, often in fixed ratios, e.g., glucose (C 6 H 12 O 6 ), hydrazine (N 2 H 4 ), silica (SiO 2 ), water (H 2 O). Condensed phase compounds (solids or liquids) may have variable compositions, e.g., YBa 2 Cu 3 O 7 x (x < 1) show superconductivity with decreasing T c as x increases. (b) Mixtures : Combination of two or more substances in which each substance retains its properties and composition. Composites are important mixtures that attempt to take advantage of the important properties of each component, e.g., polymer-metal composites. They do not have constant compositions. Mixtures are either Homogeneous : Composition of the mixture is the same throughout, e.g., solution of NaCl in water; mixture of ethanol and water – “single phase” Heterogeneous : Composition of the mixture is not uniform, e.g., mixture of oil and water; mixture of two different solids – two or more “phases” Mixtures can be separated into pure substances by physical means, i.e., heating, cooling, filtration, distillation, chromatography, crystallization, magnetism . For example, the International Nickel Company (INCO) uses magnets to separate FeS from NiS in their production process of pure Ni metal.
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Chemistry Week 1 - Chemical Fundamentals Introduction (1)...

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