Thermodynamics

# Thermodynamics - CHEMICAL THERMODYNAMICS 1. The...

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Thermodynamics 1 CHEMICAL THERMODYNAMICS 1. The thermodynamic laws 2. Thermochemistry THE THERMODYNAMIC LAWS Classical physics has three pilars: 1. mechanics 2. electromagnetism 3. thermodynamics Thermodynamics studies the flow of heat in systems. Since heat is a form of energy, it studies changes in the distribution of energy. Thermodynamics studies macroscopic properties. Thermodynamics is founded on three (or four) laws, and it builds up through deductions from these laws.

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Thermodynamics 2 The objectives are to understand the following concepts: 1. heat, heat capacity and the Zeroth Law 2. heat, work, internal energy and the First Law . 3. enthalpy and the First Law . 4. state functions 5. entropy and the Second Law . 6. the standard state and the Third Law . to distinguish between different types of processes: 1. reversible and irreversible 2. adiabatic and isothermal
Thermodynamics 3 ZEROTH LAW OF THERMODYNAMICS When two bodies that are in contact have different temperatures, heat will flow from the hotter body to the colder body until the temperatures are the same. Zeroth Law When the temperatures are the same, the system is at thermal equilibrium. The hotter body went from T h to T m . The colder body went from T l to T m . The heat given off by the hotter body was equal to s hotter m hotter (T m -T h ) The heat gained by the colder body was equal to s colder m colder (T m -T l ) hot cold hot cold heat always final minus initial Both heats were equal but with opposite sign : -s hotter m hotter (T m -T h ) = s colder m colder (T m -T l ) “s” is a proportionality constant that corresponds to the specific heat of the substance specific heat = amount of heat necessary to raise the temperature of one gram of substance one degree Celsius.

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Thermodynamics 4 Two 1 kg aluminum blocks (specific heat = 0.902 J/g.K) are placed in contact inside an insulated container, where heat cannot flow out. One block is at 350 K and another block is at 500 K. What will be the final temperature of the blocks? -s hotter m hotter (T m -T h ) = s colder m colder (T m -T l ) -0.902 J/g.K x 1000 g (T m -500 K)=0.902 J/g.K x 1000 g (T m - 350 K) - T m + 500 K = T m - 350 K 500 K + 350 K = 2 T m T m = 425 K
Thermodynamics 5 In 1850, Joule performed an experiment with the following components: An insulated container with water. adiabatic : heat cannot flow in or out of the system. A paddle that can be moved by a string connected to a weight. The weight can perform mechanical work. J m s m kg m . N : units cos d F : vectors 2 of product scalar d F work 2 A thermometer to measure the change in temperature of the water. He found that the work done on the system was proportional to the change in temperature of the water and to the mass of water. work = s m H2O T + term Mechanical energy can be converted into thermal energy (heat).

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## This note was uploaded on 05/01/2011 for the course CHEM 345 taught by Professor Cardelino during the Fall '09 term at Spelman.

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Thermodynamics - CHEMICAL THERMODYNAMICS 1. The...

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