Chemists need to characterize the products of their chemical reactions so that they can be sure of the structure and composition of the molecule(s) they have made. One common way is by measuring the melting point of a solid substance. This doesn’t provide specific information about the arrangement of chemical bonds in a molecule, though, so more advanced techniques are required to completely characterize a molecule. These techniques often involve using electromagnetic radiation to probe the energy levels in the molecules (see “Physical and Theoretical Chemistry” for more on these topics). Knowledge of what energies/wavelengths of light the molecule can absorb can be related directly to structural features of the molecule.