Chpt5 - Chapter 5 Thermochemistry Thermodynamics...

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Chapter 5 Thermochemistry
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Thermodynamics Thermodynamics is the study of energy and its transformations. Thermochemistry is the area of thermodynamics that deals with relationships between chemical reactions and energy changes involving heat.
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Energy The ability to do work or transfer heat. Work : Energy used to cause an object that has mass to move. Heat : Energy used to cause the temperature of an object to rise.
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Kinetic Energy Energy an object possesses by virtue of its motion. 1 2 E = mv
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Potential Energy Energy an object possesses by virtue of its position or chemical composition. E = mgh m = mass; g = gravitational constant (9.8 m/s 2 ); h = height
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Electrostatic Potential Energy Arises from the interaction between charged particles. κ = constant (8.99 x 10 9 J-m/C 2 ); Q 1 and Q 2 = electrical charge; d = distance κ Q 1 Q 2 d E el =
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Units of Energy The SI unit of energy is the joule (J) . An older, non-SI unit is still in widespread use: The calorie (cal) . 1 cal = 4.184 J 1 Cal = 1000 cal = 1kcal 1 J = 1  kg·m 2 s 2
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System and Surroundings The system includes the molecules we want to study (here, the hydrogen and oxygen molecules). The surroundings are everything else. Closed systems (systems that exchange energy but not matter with their surroundings) are the most readily studied.
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Work Energy used to move an object over some distance. w = F d , where w is work, F is the force, and d is the distance over which the force is exerted.
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Heat Heat is the energy that is transferred between a system and its surroundings due to a difference in temperature. Energy can also be transferred as heat. Heat flows from warmer objects to cooler objects.
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Transferal of Energy a) The potential energy of this ball of clay is increased when it is moved from the ground to the top of the wall.
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Transferal of Energy b) As the ball falls, its potential energy is converted to kinetic energy.
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Transferring Energy c) When it hits the ground, its kinetic energy falls to zero (since it is no longer moving); some of the energy does work on the ball, the rest is dissipated as heat.
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First Law of Thermodynamics Energy is neither created nor destroyed.
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This note was uploaded on 04/25/2008 for the course CHEM 131 taught by Professor Sykora during the Spring '08 term at S. Alabama.

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Chpt5 - Chapter 5 Thermochemistry Thermodynamics...

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