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Class02 - Science of Chemistry Science is knowledge...

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Science of Chemistry Science is knowledge obtained by making, organizing, and explaining observations
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Joesten,”Essentials”,Saunders, 1993, 3 Chemistry is a discipline of natural science, which is concerned with knowledge about matter (anything that occupies space and has mass) and energy (that which is able to cause motion of matter) Study of Non-living Matter
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Chemistry Composition of matter Structure of matter Properties of matter Changes that matter undergoes and the associated energies Contents of the discipline of chemistry Organize observations Explain observations
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Composition of Matter - description of components of samples and how they are combined Compound ( Combination of elements in fixed ratios shown as subscripts in formulas : H 2 O, NaCl) Element ( Simplest substance - represented by symbols : H, O, Na, Cl) Pure Substance (Fixed composition and homogeneous) Mixture (Variable composition - combination of elements and/or compounds) Homogeneous ( Uniform: solution of NaCl in H 2 O) Heterogeneous ( Non-uniform: NaCl and pepper)
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Physical Properties (observation does not require a change in composition) Chemical Properties (observation requires change in composition) Properties of Matter - identifying characteristics Melting point Boiling point Density Color Odor Reacts with water Reacts with oxygen Inert Explosive Flammable
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Physical Changes (involve no change in composition) Chemical Changes (involve change in composition) Changes in Matter Melting, boiling, etc. Burning, decomposing, etc. These changes in matter are always accompanied by changes in energy with physical changes involving less energy than chemical changes
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http://www.grc.nasa.gov/WWW/K-12/airplane/state.html cool heat cool heat Changes in states of matter require changes in energy
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Stoker, H.S., Chemical Principles, 3rd, MacMillan, NY, 1990 Endergonic Changes - energy is required continuously. Called endothermic if energy is heat. Exergonic Changes - energy is produced continuously. Called exothermic if energy is heat. Energy changes Measured by temperature
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http://www.magnet.fsu.edu/education/tutorials/magnetacademy/superconductivity101/page4.html Temperature is a measure of average kinetic energy (motion of molecules) F = 9/5 C + 32 K = C + 273 Motion of molecules increasing
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Structure of Matter Component particles (atoms or particles derived from atoms) Relative locations of particles (described using terms from geometry)
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Atoms (symbol: H, O) Molecules (symbols with subscripts: H 2 O) combine Ions (symbol with superscript showing charges: H + , O 2- ) gain or lose electron(s) Kinds of Particles What kinds of particles are derived from atoms?
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What is the general structure for substances composed of ions? Ions exist in repeating patterns that maximize distances between ions having like charges and minimizes distances between ions having opposite charges A sample of a substance made up of ions may contain any number of ions, but the total positive charge must equal the total negative charge The substance is represented by an empirical
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