Chapter 7

# Chapter 7 - Chapter 7 7.1 Energy is the capacity to make...

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Chapter 7 7.1 “Energy” is the capacity to make things move. “Kinetic Energy” is the energy something that’s already moving around has. “Potential Energy” is energy that’s stored somehow, and ready to make something move. Energy is conserved, like atoms; it is never created or destroyed. It can be converted from kinetic to potential energy and back again, or from one place/thing to another, but never created or destroyed. Energy is measured in units of “Joules”. One Joule is equal to 1Nm or 1 (kgm^2/s^2) It’s a relatively small amount of energy (it takes 4.184J to increase the temperature of one gram of water one degree Celsius), so we frequently use kilojoules (kJ) An older unit of energy is the “calorie” (cal), and is equal to 4.184J. The energy of foods is measured in “dietary calories” Cal, which are equal to 1 kcal. 7.2 The molecules of a substance are in constant motion. They fly around relative to one another (“translate”), spin (“rotate”) and vibrate. All of these motions have kinetic energy associated with them The sum of al these kinetic energies for all the molecules in a sample is the “Internal Energy”. Internal energy is often represented with the letters E or U. The internal energy is an extensive property of a system. Extensive properties are those that depend on the amount of stuff (number of molecules) in a system. The average kinetic energy associated with each of these motions is the “Temperature”. The temperature is an intensive property of a system. Intensive properties are those that do not depend on the amount of stuff (number of molecules) in a system. Temperature is usually represented with the letter T.

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## This note was uploaded on 09/18/2008 for the course CHEM 1000 taught by Professor Moore during the Spring '08 term at St. John's.

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Chapter 7 - Chapter 7 7.1 Energy is the capacity to make...

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