Endothermic & Exothermic Chemical Reactions

Classifying Reactions  Reactions can be classified based on whether the change involves an absorption of energy or a release of energy.  These reactions are termed: 1.Endothermic 2.Exothermic

Endothermic Reactions  A reaction in which energy is absorbed from the surrounding environment as the products form  Molecules, atoms and bonds gain or energy from their surroundings.  The container in which an endothermic reaction is taking place will feel cold.

Exothermic Reactions  Reaction in which energy is released by the system into the surrounding environment as products form.  Molecules, atoms and bonds lose energy to their surroundings.  The container in which an exothermic reaction is taking place will feel warm.

Exothermic Reactions - Examples  Sodium metal dropped into a beaker of water causes an explosion.  Sweat beads form on your forehead after a heavy workout.  Cellular Respiration  The freezing of a substance.  Glow Sticks  Fireworks  Condensation

Endothermic Reactions - Examples  Ice melts on a counter top.  Green plants need sunlight for growth (Photosynthesis)  Cold packs