Molecules interact with each other in a variety of ways. The process of smelling involves interactions between the molecules that enter the nose and the molecules that make up the lining of the nose. One key to molecular interactions is the fact that atoms in a molecule often do not share electrons equally. This unequal sharing creates partial positive and negative charges on different atoms in the molecule. These partial charges influence how molecules interact with each other and help to determine properties like phase, smell, and whether the substance will dissolve in another substance. Molecular size, shape, and bonding patterns all contribute to smell.