Depends on the context in which you ask the question: if it's your choice we're discussing, no one's going to be able to rationalize your behavior but you; if you're a physicist and trying to rationalize the behavior of your offspring ("Where did we go wrong?"), see a family counselor; if you're trying to define the nature of questions and answers that are answered in detail by chemists, as a sub-field of physics, as compared to the nature of questions and answers physicists present to describe identical phenomena, physics is the organized study of the properties of and interactions of matter and energy (or if you wish to be "relativistic," of energy or matter), that is, everything there is, while chemistry is the study of the properties and interactions of atoms and molecules as isolated entities, in bulk, and in "simple" mixtures.