1422-Chapt-15-Thermodynamics

# 1422-Chapt-15-Thermodynamics - Chapter 15(not much on E...

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Chapter 15 (not much on E) Thermodynamics: Enthalpy, Entropy & Gibbs Free Energy

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Thermo 2 Thermodynamics: thermo = heat (energy) dynamics = movement, motion Some thermodynamic terms chemists use: System: the portion of the universe that we are considering open system: energy & matter can transfer closed system: energy transfers only isolated system: no transfers Surroundings: everything else besides the system Isothermal: a system that is kept at a constant temperature by adding or subtracting heat from the surroundings. Heat Capacity: the amount of heat energy required to raise the temperature of a certain amount of material by 1°C (or 1 K). Specific Heat Capacity: 1 g by 1°C Molar Heat Capacity: 1 mole by 1°C
Thermo 3 Calorie: the amount of heat required to raise the temperature of 1g of water by 1°C. specific heat of water = 1 cal/g °C 1 calorie = 4.18 joules Specific Heats and Molar Heat Capacities Substance Specific Heat (J/°C g) Molar Heat (J/°C mol) Al 0.90 24.3 Cu 0.38 24.4 Fe 0.45 25.1 CaCO 3 0.84 83.8 Ethanol 2.43 112.0 Water 4.18 75.3 Air 1.00 ~ 29 important to: engineers chemists EXAMPLE: How many joules of energy are needed to raise the temperature of an iron nail (7.0 g) from 25°C to 125°C? The specific heat of iron is 0.45 J/°C g. Heat energy = ( specific heat )( mass )( T ) Heat energy = ( 0.45 J/°C g )( 7.0 g )( 100°C ) = 315 J Note that T can be ºC or K, but NOT ºF. When just T is being used in a scientific formula it will usually be kelvin (K).

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