1. 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

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 flask ISOLATED SYSTEM: can exchange neither energy nor matter with its surroundings (e.g. a thermos flask)

3. 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

4. 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

5. Exothermic and Endothermic Processes