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
- 5. Exothermic and Endothermic Processes
- 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)