M2_1-student - Unit 1 How do we distinguish substances?...

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Chemistry XXI Unit 1 How do we distinguish substances? Module 2: Modeling Matter Central goal: To explain the diversity in properties and behaviors of the different substances in a system based on the particulate model of matter.
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Chemistry XXI The Challenge Modeling How do I explain it? Diversity in life and materials around us is, in many ways, a consequence of the existence of different substances in our world. What causes the differences? What models could allow us to explain , predict , and even design , these differences? Carbon dioxide Nitrogen Water
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Chemistry XXI Answering Questions How do we explain that oxygen has a higher boiling point than nitrogen? Why do liquids get colder when they evaporate? Why does the boiling point of water increases with increasing pressure? Why do gases cool down under rapid expansion? For example,
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Chemistry XXI Particulate Model of Matter One of the most powerful models we have to explain and predict the physical properties and behavior of substances is the particulate model of matter. 1 mL of water = 33444444444444444444444 particles = Solid Liquid Gas Basic Assumptions: 1. Any macroscopic sample of a substance is composed of a large number of very small particles;
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Chemistry XXI 0.0000001 m = 10 -7 m 0.00001 m = 10 -5 m 0.001 m = 10 -3 m 0.01 m = 10 -2 m 0.1 m = 10 -1 m How Small? 1 m Most substances are made of particles of “nanometer” size.
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Chemistry XXI Solid Liquid Gas What do these “particles” represent? What are the limitations of these representations? Particles could represent anything we want: atoms, molecules, ions. These representations are static , have unrealistic proportions , represent particles as solid objects , mix levels of representation . Being Cautious
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Chemistry XXI 2. Particles are constantly moving; Dynamic Nature Basic Assumptions: Temperature is a measure of average kinetic energy per particle: In this model: Pressure is determined by the force of the particle collisions on the walls: Pressure = Force/Area
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This note was uploaded on 04/09/2009 for the course CHEM 151 taught by Professor Staff during the Fall '08 term at University of Arizona- Tucson.

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M2_1-student - Unit 1 How do we distinguish substances?...

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