Temperature Heat and Energy Transfer Energy of Phase Change Measure of hotness Celsius 0o freezing point of pure water at standard pressure 100o boiling point at standard pressure Fahrenheit 0o was lowest attained 32 was his age when he performed experiments 212 is boiling point in those increments Temperature Convert with equations 5 C F 32 9 Order of operations Parentheses first Then multiply or divide Add or subtract last Or use adjacent scales such as p 142 of Conceptual Physical Science textbook 9 F C 32 5 Heat Calorie Amount of heat required to raise the temperature of 1 gram of pure water 1o C Food Calories are kilocalories Joule of calorie Temperature Kelvin same size as degree Celsius Absolute Zero is 0 K notice no degree symbol on K 0o C 273 K Molecular motion ceases at absolute zero Laws of Thermodynamics 1 Heat added increase in thermal energy external work done by the system 2 Heat never spontaneously flows from a cold substance to a hot substance 3 No system can reach absolute zero 1 cal 4 184 J 1 Entropy Natural increase of randomness in system Energy spreads to disorder in the system Does not spontaneously reform gasoline from carbon dioxide and water Heat Expansion Random motion causes substance to be bigger Liquids usually have greater heat expansion than solids Thermostats use different expansion of different type of metals Specific Heat Capacity Quantity of heat needed to change the temperature of given amount of a substance 1o C Water very high specific heat capacity Maritime areas more mild temperature than continental areas Takes 1 8 calorie to raise temperature of iron 1o C Water Expansion Unusual response to cooling Contracts until reaching 4o C Expands slightly upon further cooling to 0o C Expands 9 upon freezing http www alaskarails org terminology questions html http demo physics uiuc edu LectDemo scripts demo descript idc DemoID 40 Water Molecule Bent Polar Water Expansion Molecule shape fit together closer in liquid Open structured crystal due to hydrogen bonding of polar molecules upon freezing 2 Water Expansion Heat Transfer conduction Tile is a better conductor of heat than the wood floor http www elmhurst edu chm vchembook 122densityice html Heat Transfer convection Currents from heater shown by shadows Heat Transfer radiation Does not need material to transfer radiant energy Dark bodies absorb it better than light colored ones Radiant Energy All objects emit thermal energy Visible light above 500oC Re emit absorbed radiation at wavelength according to temperature Good absorbers are good emitters Poor absorbers are poor emitters Heat Transfer Conduction Direct molecule interaction Transferring energy to next molecule Convection Movement of fluid liquid or gas Radiation Through open space Electromagnetic radiation 3 Phases of Matter Three phases of water Solid Liquid Gaseous or vapor Plasma http www cdli ca CITE glaciers htm Gas Solid and Liquid Evaporation Kinetic energy of molecules great enough to escape surface Energy is taken from liquid cools it Gaseous phase or vapor phase Zumdahl Zumdahl DeCoste World of Chemistry 2002 page 441 http www unit5 org christjs Matter 20and 20Energy Unit 202 20PP files frame htm Gas Steam Water vapor H2O g Steam http www unit5 org christjs Matter 20and 20Energy Unit 202 20PP files frame htm http en wikipedia org wiki Water vapor 4 Evaporation or Not Condensation Opposite of evaporation Kinetic energy of molecules running into surface of liquid and joining it Heats environment http www geology sdsu edu classes geol351 01watercycle watercyclefigs htm Condensation on Glass Liquid Water H2O l Water http www geology sdsu edu classes geol351 01watercycle watercyclefigs htm http www unit5 org christjs Matter 20and 20Energy Unit 202 20PP files frame htm Atmosphere Evaporation Energy goes into air Cools remaining water Condensation Energy goes from air to surface Warms local environment Atmosphere Warm air has greater capacity for holding water in the vapor phase Saturation at capacity Relative Humidity percent of water contained compared to saturated amount at that temperature 5 Water Vapor Capacity http www wdtv com weather images Weather Review humidity htm Condensation diagram http weatherstreet com weatherquestions What is condensation htm Condensation http observe arc nasa gov nasa earth hydrocycle graphics condensation jpg Sea Fog http www anythingmarine co uk anything met htm Coastal fog http www victoriaweather ca clouds php image fog Boiling http www chem purdue edu gchelp liquids boil2 html 6 Boiling http www deepseaimages com dsilibrary showphoto php photo 2912 password sort 1 size medium cat 853 page 1 Pressure Cooker http www goodmans net get item ma 6qt maitres 806212 6 qt cooker htm Boiling Temp vs Pressure Microscopic boiling http www chem purdue edu gchelp liquids boil2 html Pressure canner http hgic clemson edu factsheets HGIC3020 htm Boiling at less than 100 o C Pour in hot water Reduce Pressure with syringe http www micrecol de air2 html http www chem purdue edu gchelp liquids boil2 html 7 Energy of Water Phase Change Energy of phase change for water Calorie energy to change 1 g water 1 K or 1 oC Also need energy to change to different state of matter Energy of vaporization condensation 540 calories per gram of water 2256 J g Energy of melting freezing 80 calories per gram 334 J g http hyperphysics phy astr gsu edu hbase thermo phase html Molecular Structure of Ice Solid Ice H2O s Ice Zumdahl Zumdahl DeCoste World of Chemistry 2002 page 455 http www unit5 org christjs Matter 20and 20Energy Unit 202 20PP files frame htm http www unit5 org christjs Matter 20and 20Energy Unit 202 20PP files frame htm Solid Liquid Gas http www unit5 org christjs Matter 20and 20Energy Unit 202 20PP files frame htm 8
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