Chemistry 2 Monday, August 28, 2006

Chemistry 2 Monday, August 28, 2006 - ** Almost all...

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Monday, August 28, 2006 Chemistry CASH OR CHARGE? - How do charges govern energy? - How were electrons discovered? Text : Sections 1.6 - 1.8 (first 2 parts) CHARGE AND ENERGY 1. +/- charges (Ben Franklin) a. Opposite charges attract like charges repel 2. Potential Energy stored in interacting charges a. E: energy of interaction Note difference between force and energy Ex. 1.8 in text (p.16) parts “a” and “b” reversed 3. Coulomb’ Law E = k q 1 q 2 εε r q 1 2 = charges r = distance between charges ε = insulating ability of “median” ( = 1 for vacuum) k = constant “lower E” = more negative +1 +1 (+1)(+1) = 1 +2 1 like most charges energy +1 +1 (+1)(+1) +1 = 2 .5 0 +1 -1 (+1)(-1) -1 = -1 opp. least 1 charges energy -2 +1 -1 (+1)(-1) = -2 .5
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Monday, August 28, 2006 PLOTS OF E vs. DISTANCE 2 2 1 1 -2 -1 1 2 -2 -1 1 2 -1 -1 -2 -2 Like Charges Opposite Charges *Systems in nature usually seek the lowest E possible (nature is lazy)
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Unformatted text preview: ** Almost all chemistry is based on the interaction of charges seeking the lowest E DISCOVERY OF ELECTRONS 1. How do materials (and atoms) acquire charge? (Dalton = neutral atoms) 2. Thomson: cathode ray experiment. Phosphorescent Power--Screen--+ Cathode Rays + Extra Field: OFF Distance depends SMALL on charge/mass ratio LARGE Conclusions-Charged particles- Large charge/mass ratio- Large charge or really small mass could Monday, August 28, 2006 MILLIKAN: OIL-DROP EXPERMENT charge gravity +1 X-rays ionize air e- stick to drop-1-measure charge-calculate mass (from Thomson’s charge/mass)-1/1800 th of H-atom NEW MODEL OF ATOM GOALS-Compare energies at different charges at different distances-Describe the experiments that led to the discovery and mass of the e-...
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This note was uploaded on 03/20/2008 for the course CH 101 taught by Professor Bigham during the Fall '08 term at N.C. State.

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Chemistry 2 Monday, August 28, 2006 - ** Almost all...

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