What is the reaction of breaking down substances into simpler components?

In breaking-down reactions one substance breaks up into a number of smaller ones. For example, some photographic film is coated with silver chloride

(AgCl), a substance that breaks down when light falls on it, leaving a dark image, or negative, on the film. Two products are formed from this reaction, silver

(Ag) and chlorine gas (Cl2). The reaction could be written:

• as a Word equation: silver chloride → silver + chlorine

• as an unbalanced formula equation: AgCl → Ag + Cl2

• showing the states of matter: AgCl(s) → Ag(s) + Cl2 (g)

Breaking-down reactions are also known as decomposition reactions. Source: Science Dimentions 2 textbook