This document discusses writing and balancing chemical reactions. It explains that when writing chemical equations, reactants are written on the left and products are written on the right. It also notes that every atom must be balanced according to the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction. The document indicates that if an equation is not balanced, a coefficient can be placed in front of a molecule to balance the number of atoms, but no bonds can be broken in the process of balancing equations.