We'll learn about the five major types of chemical reactions: synthesis, decomposition, synthesis, single replacement (also called single displacement) and double replacement (also called double displacement). We'll look at examples of each, so that you can classify them, figuring out what type they are. In a synthesis reaction, a compound is made from more simple materials. In a decomposition reaction, a compound breaks down into simpler elements or compounds. In a combustion reaction, a compound (usually with carbon, hydrogen, and sometimes oxygen) combines with oxygen to give carbon dioxide and water. In a single replacement (displacement) reaction, one element that is on its own displaces another element in aqueous solution, kicking it out. In a double replacement (displacement) reaction, the positive and negative ions in two ionic compounds switch places, causing a precipitate to form.