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Thermo#2

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gbsliebs2002

This document defines different types of systems and their interactions with surroundings in thermodynamics. An open system can exchange both matter and energy with surroundings, a closed system can only exchange energy, and an isolated system cannot exchange either. Exothermic processes release heat to surroundings while endothermic processes absorb heat from surroundings. Specific examples of endothermic processes that require energy input include vaporization and melting, while freezing is exothermic and releases energy.

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SYSTEM OPENISOLATED CLOSEDSystems & SurroundingsIn thermodynamics, the world is divided into a system and its surroundingsA system is the part of the world we want to study (e.g. a reaction mixture in a flask)The surroundings consist of everything else outside the system
OPEN SYSTEM: can exchange both matter and energy with the surroundings (e.g. open reaction flask, rocket engine)CLOSED SYSTEM: can exchange only energy with the surroundings (matter remains fixed) e.g. a sealed reaction flaskISOLATED SYSTEM: can exchange neither energy nor matter with its surroundings (e.g. a thermos flask)
ExothermicA chemical reaction or a physical change that releases heat -energy flows out as a result of a temperature difference between the system and the surroundingsExothermic processes have negative q reaction
EndothermicA chemical reaction or a physical change in which heat is absorbed - energy flows into a system from the surroundings.Endothermic processes have positive q reaction
Exothermic and Endothermic Processes
VaporisationEnergy has to be supplied to a liquid to enable it to overcome forces that hold molecules together endothermic process (q is positive)MeltingEnergy is supplied to a solid to enable it to vibrate more vigorously until molecules can move past each other and flow as a liquid endothermic process (q is positive)FreezingLiquid releases energy and allows molecules to settle into a lower energy state and form a solid exothermic process (q is negative)(we remove heat from water when making ice in freezer)

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Thermo#2

  • 1. SYSTEM OPENISOLATED CLOSEDSystems & SurroundingsIn thermodynamics, the world is divided into a system and its surroundingsA system is the part of the world we want to study (e.g. a reaction mixture in a flask)The surroundings consist of everything else outside the system
  • 2. OPEN SYSTEM: can exchange both matter and energy with the surroundings (e.g. open reaction flask, rocket engine)CLOSED SYSTEM: can exchange only energy with the surroundings (matter remains fixed) e.g. a sealed reaction flaskISOLATED SYSTEM: can exchange neither energy nor matter with its surroundings (e.g. a thermos flask)
  • 3. ExothermicA chemical reaction or a physical change that releases heat -energy flows out as a result of a temperature difference between the system and the surroundingsExothermic processes have negative q reaction
  • 4. EndothermicA chemical reaction or a physical change in which heat is absorbed - energy flows into a system from the surroundings.Endothermic processes have positive q reaction
  • 6. VaporisationEnergy has to be supplied to a liquid to enable it to overcome forces that hold molecules together endothermic process (q is positive)MeltingEnergy is supplied to a solid to enable it to vibrate more vigorously until molecules can move past each other and flow as a liquid endothermic process (q is positive)FreezingLiquid releases energy and allows molecules to settle into a lower energy state and form a solid exothermic process (q is negative)(we remove heat from water when making ice in freezer)