CH302%20Zumdahl%20Chapter%209%20thermodynamics%20review%20sp08

# CH302%20Zumdahl%20Chapter%209%20thermodynamics%20review%20sp08

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1 Chapter 9 - Review Thermodynamics: The First Law 2 The Nature of Energy ± Thermodynamics is the study of the transformation of energy. ± There are two laws that govern the study of thermodynamics. 1. The first law keeps track of energy changes by allowing us to calculate how much heat is generated during a reaction. 2. Provides explanations for why some reactions occur and others do not. 3 The Nature of Energy ± English physicist, James Joule, showed that both heat and work are forms of energy in the middle 1800’s. ² Energy is the capacity to do work ² Energy is the capacity to produce heat ± Energy may be ² Transformed from one form to another ² Transferred from one place to another

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4 The Nature of Energy ± The law of conservation of energy states that energy can be converted from one form into another but can neither be created or destroyed. ² The energy of the universe is constant. ± Energy may be classified as: ² Potential energy - energy that matter possesses by virtue of its position, condition, or composition. ² Kinetic energy - energy that matter possesses by virtue of its motion. 5 The Nature of Energy Chemical systems tend toward a state of minimum potential energy. ² Examples of this include: ² Combustion reactions release heat energy. ² Acid/base reactions release heat energy. 6 The Nature of Energy Kinetic Energy – is the energy due to motion. ± The kinetic energy of an object is due to its motion and is dependent on the its mass and its velocity. K.E. = ½m υ 2 m = mass υ = velocity
7 Systems To keep track of energy, the world is divided into: ± A system – the substances involved in the chemical and physical changes that we are interested in studying. ² The reactants and products of a reaction. ² The condition of a substance before and after a change of state. ± The surroundings – everything in the system’s environment. ² A water bath in which a reaction mixture may be immersed. ² The surroundings are where observations are made on the energy transferred into or out of the system. 8 Systems The universe – is the system plus the surroundings. ± However, the part of the actual universe that is affected usually consists of a sample, a flask, and a water bath. 9 The system is the sample or the reaction mixture of interest. • Reactants and products of the reaction Outside the system are the surroundings . • The reaction container, the room, and everything else other than the reactants and products. The system plus its surroundings is called the universe .

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10 Energy and matter can be exchanged with its surroundings Energy but not matter can be exchanged with its surroundings Neither energy nor matter can be exchanged with its surroundings A system can be open, closed or isolated .
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## This note was uploaded on 09/20/2008 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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CH302%20Zumdahl%20Chapter%209%20thermodynamics%20review%20sp08

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