Thermo#2

SYSTEM OPEN ISOLATED CLOSED Systems & Surroundings In thermodynamics, the world is divided into a system and its surroundings A 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 flask ISOLATED SYSTEM: can exchange neither energy nor matter with its surroundings (e.g. a thermos flask)

Exothermic A chemical reaction or a physical change that releases heat -energy flows out as a result of a temperature difference between the system and the surroundings Exothermic processes have negative q reaction

Endothermic A 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

Vaporisation Energy has to be supplied to a liquid to enable it to overcome forces that hold molecules together ,[object Object],Melting Energy is supplied to a solid to enable it to vibrate more vigorously until molecules can move past each other and flow as a liquid ,[object Object],Freezing Liquid releases energy and allows molecules to settle into a lower energy state and form a solid ,[object Object],(we remove heat from water when making ice in freezer)

Thermo#2

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