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
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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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Thermo 4 Problem: How much energy does it take to raise the body temperature 2.5ºC (a fever of just over 103ºF) for someone who weighs 110 pounds (50 kg). Assume an average body specific heat capacity of 3 J/ºC.g. Problem: What would be more effective at melting a frozen pipe – hot water or a hair dryer (hot air gun). Why?
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Thermo 5 State Functions System properties, such as pressure ( P ), volume ( V ), and temperature ( T ) are called state functions . The value of a state function depends only on the state of the system and not on the way in which the system came to be in that state. A change in a state function describes a difference between the two states. It is independent of the process or pathway by which the change occurs. For example, if we heat a block of iron from room temperature to 100°C, it is not important exactly how we did it. Just on the initial state and the final state conditions. For example, we could heat it to 150°C, then cool it to 100°C. The path we take is unimportant, so long as the final temperature is 100°C. Miles per gallon for a car, is NOT a state function. It depends highly on the path: acceleration, speed, wind, tire inflation, hills, etc. Most of the thermodynamic values we will discuss in this chapter are state functions.
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Thermo 6 Energy: "The capacity to do work and/or transfer heat" Forms of Energy: Kinetic (E kinetic = ½ mv 2 ) Heat Light (& Electromagnetic) Electricity Sound Potential Gravitational Chemical Nuclear - Matter (E = mc 2 )  WORK
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Thermo 7 First Law of Thermodynamics: The total amount of energy (and mass) in the universe is constant.
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This note was uploaded on 11/12/2011 for the course CHEM 1422 taught by Professor Staff during the Fall '08 term at LSU.

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

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