This document summarizes endothermic and exothermic reactions. It defines physical and chemical changes, noting indicators of chemical changes like temperature change, odor change, formation of precipitates, and sometimes color change. Exothermic reactions release energy to the surroundings, lowering their temperature, while endothermic reactions absorb energy from the surroundings, raising their temperature. Examples of exothermic reactions given are combustion, evaporation of water, and the mixing of sodium and chlorine to form table salt. Examples of endothermic reactions include cold packs and melting ice. The document also discusses activation energy, cellular respiration, photosynthesis, and conduction of two experiments on exothermic reactions involving citric acid/baking soda and steel wool