water 3-10

S example na1 cl 1 s water discourages re association

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Unformatted text preview: Water "discourages" re-association of oppositely charged compounds. s States of Water s Liquid: Liquid Between 0 and 100C. s Flow properties are due to H bonds that link adjacent molecules. s Without H bonds water = gas because of its small mass. s H bonds are constantly breaking and reforming. Hydrogen Bonds H H O H O H States of Water s Warming water requires one calorie per gram per degree Celsius (1 cal/g/C): Specific heat s Water has high specific heat = absorbs a lot of heat with small change in temperature. s This is used to cushion foods against rapid rise in temperature. States of water Examples: Heat food in a boiler rather than putting directly on flame. s Putting custard in pan of water in the oven. s Fats have much lower specific heat; Olive oil = 0.471 s A pan of oil will heat to temperature twice as fast as a pan of water. s States of Water Materials used to make cooking utensils have a low specific heat; aluminum = 0.214 cast iron = 0.119 s Surface Tension: The attraction Tension between molecules at the surface of a liquid. s The effort or pressure to be in gaseous state = vapor pressure. pressure s States of Water s Crystalline: Lowest energy. s Motion of molecules is slowed s Volume shrinks slightly and hydrogen bonds last longer. s Water is densest at 4 C (1 g/cc). s Molecules begin to associate in precise arrangement. States of Water At 0C the actual phenomenon of freezing takes place s 79.6 cal/g are removed from the system (heat of fusion). s This removal of heat is not accompanied by change of temperature. s When ice is melting this heat is needed to disrupt H bonds and melt the ice. s States of Water s When ice melts, temperature begins to rise. s As a result of expansion (9%) ice is less dense than water. s Expansion causes vegetable cell walls to rupture when frozen. States of Water GAS: Highest energy state s Water vapor or steam s Evaporation = water molecules obtain enough kinetic energy. s Random motion to break hydrogen bonds and escape into atmosphere. s H-bonds break and refor...
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This note was uploaded on 04/08/2013 for the course NUSC 3233 taught by Professor Mariafernandez during the Fall '10 term at UConn.

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