Types of chemical reaction

Chemical reactions can be grouped by the way atoms rearrange. In a combination reaction two or more substances join to make one product (A + B → AB). In a decomposition reaction one substance breaks down into two or more simpler ones (AB → A + B), usually needing heat, light or electricity. In a displacement reaction a more reactive element pushes a less reactive one out of its compound (A + BC → AC + B). In a double displacement reaction two compounds swap partners (AB + CD → AD + CB), often forming a precipitate or water.