Chemical reactions can be recognized by careful observations. The production of a precipitate, a color change, evolution of a gas, or a transfer of energy are all clues that a chemical change is occurring. In the picture above, a copper sheet has been placed into a colorless solution of silver nitrate. The reaction slowly produces silver metal, which clings to the surface of the copper sheet. The other product of the reaction is aqueous copper(II) nitrate, which is blue in color. In this chapter, we begin to advance beyond simply recognizing chemical reactions by writing chemical equations that describe how the reactants in a given reaction are converted into products. Classifying chemical reactions into several distinctive categories will aid you in predicting the products of many different chemical reactions.
Flickr:Shandchem. www.flickr.com/photos/14508691@N08/3498221509/. CC BY 2.0.