Chapter 6 Thermochemistry
Definitions #1 Energy : The capacity to do work or produce heat Potential Energy : Energy due to position or composition Kinetic Energy : Energy due to the motion of the object 2 1 2 KE mv 6.1 The Nature of Energy
• In the initial position, ball A has a higher potential energy than ball B. Initial Position 6.1 The Nature of Energy
• After A has rolled down the hill, the potential energy lost by A has been converted to random motions of the components of the hill and to the increase in the potential energy of B. Final Position 6.1 The Nature of Energy
Definitions #2 Law of Conservation of Energy: The First Law of Thermodynamics : The total energy content of the universe is constant energy can be converted from one form to another but can be neither created nor destroyed. The total energy content of the universe is constant. 6.1 The Nature of Energy
• Heat - involves the transfer of energy between two objects due to a temperature difference. • Work – force acting over a distance. • Energy - is a state function; work and heat are not: State Function – property that does not depend in any way on the system’s past or future (only depends on present state). 6.1 The Nature of Energy
• System – part of the universe on which we wish to focus attention. • Surroundings – include everything else in the universe. Chemical Energy 6.1 The Nature of Energy
• Endothermic Reaction: Heat flow is into a system. Absorb energy from the surroundings. • Exothermic Reaction: Energy flows out of the system. • Energy gained by the surroundings must be equal to the energy lost by the system. Chemical Energy 6.1 The Nature of Energy
Concept Check Classify each process as exothermic or endothermic . Explain. The system is underlined in each example. a) Your hand gets cold when you touch ice. b) The ice gets warmer when you touch it. c) Water boils in a kettle being heated on a stove. d) Water vapor condenses on a cold pipe. e) Ice cream melts. Exo Endo Endo Exo Endo 6.1 The Nature of Energy
• Law of conservation of energy is often called the first law of thermodynamics.
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