Chemical Changes

Chemical changes are changes in which a substance is changed into a different substance. Chemical changes occur when a chemical reaction causes bonds between atoms to break or to form. (Some in completely new forms.) Evidence that a chemical change has occured might include: a color change (not always the best evidence), an odor change, formation of a precipitate (you mix two liquids and make a solid), gas is formed (bubbles), changes in physical properties. During a chemical change, energy can be released in the form of: heat and light. When a chemical change occurs, energy is either released or absorbed. Exothermic is when heat is released. Endothermic is when goes in a substance.