The attractions of molecules for each other are called intermolecular interactions to distinguish them from covalent and ionic bonding, forms of intramolecular interactions. For very large molecules, such as proteins, nucleic acids, and synthetic polymers, non-covalent interactions of groups that make up the molecules (functional groups) have the same characteristics as intermolecular interactions even though they may actually take place between groups within the same molecule. The interactions that lead to specific shapes of enzymes, referred to as protein-folding interactions, is an example. Intermolecular interactions are most significant in liquid and solid phases where molecules are very close together. In fact, even in liquids and solids intermolecular interactions are only strong for molecules that are next to each other. The interactions of molecules in the liquid and solid states have significant consequences that are readily observable. The strength of intermolecular interactions affects numerous properties, including boiling...