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:notransfers Surroundings:everything else besides the system Isothermal:a system that is kept at a constant temperatureby 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 joulesSpecific Heats and Molar Heat Capacities Substance Specific Heat (J/°Cg) Molar Heat (J/°Cmol) Al 0.90 24.3 Cu 0.38 24.4 Fe 0.45 25.1 CaCO30.84 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/°Cg. Heat energy = (specific heat)(mass)(T) Heat energy = (0.45 J/°Cg)(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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