8.2 Temp and Heat

# 8.2 Temp and Heat - Phase transitions 8.2 Temperature and...

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1 8.2 Temperature and Heat Phase Transitions Ideal gas Law Kinetic Theory of the Ideal gas Phase transitions Typical phase diagram. Boiling temperature and melting temperature depend on pressure. Triple point is unique. Phase diagram for ice Ice is less dense than water Increasing pressure lowers the freezing point Pressure causes ice to melt. Water at the bottom of lakes does not freeze in winter. Heat of transformation is reversible +Q -Q solid liquid Heat is absorbed on melting Heat is released on solidification Hand warmer crystaline salt hydrated saturated salt solution A supersaturated salt solution can be triggered to crystallize by a mechanical pulse. Heat is released. +Q -Q Solar Heat Storage David Allen’s Solar Home in Utah www.allanstime.com/SolarHome/ Glauber’s Salt . Melting point 90 o F. L f =83 calories/g Solar heat is used to melt salt during the day Heat is released during freezing at night to heat the house. Salt Chamber

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2 Heat of fusion Heat released when water freezes can be used to save crops from freezing. Heat of evaporation Heat of vaporization provides energy for hurricanes. Thermal power Consider 1 inch of rain falling in an area of 1km 2 . Calculate the thermal energy released v Qm L = v AhL 33 2 3 (1000kg/m )(10 m) (.025m)(2257x10 J)
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## This note was uploaded on 06/01/2009 for the course PHYS phys2c taught by Professor Okamura during the Spring '09 term at UCSD.

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8.2 Temp and Heat - Phase transitions 8.2 Temperature and...

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