The Scope of Chemical Science

Chemistry is too universal and dynamically-changing a subject to be confined to a fixed definition; it might be better to think of chemistry more as a point of view that places its major focus on the structure and properties of substances— particular kinds of matter— and especially on the changes that they undergo.

In some ways, physics might be considered more "fundamental" to the extent that it deals with matter and energy in a more general way, without the emphasis on particular substances. But the distincion can get pretty fuzzy; it is ultimately rather futile to confine any aspect of human endeavour to little boxes.

Chemistry: the central science

The real importance of Chemistry is that it serves as the interface to practically all of the other sciences, as well as to many other areas of human endeavor. For this reason, Chemistry is often said (at least by chemists!) to be the "central science".
Chemistry can be "central" in a much more personal way: with a solid background in Chemistry, you will find it far easier to migrate into other fields as your interests develop.

Chemistry can enhance any career. Chemistry is so deeply ingrained into so many areas of business, government, and environmental management that some background in the subject can be useful (and able to give you a career edge as a team member having special skills) in fields as varied as product development, marketing, management, computer science, technical writing, and even law.

So just what is chemistry?

Do you remember the story about the group of blind men who encountered an elephant? Each one moved his hands over a different part of the elephant's body— the trunk, an ear, or a leg— and came up with an entirely different description of the beast.

Chemistry can similarly be approached in different ways, each yielding a different, valid, (and yet hopelessly incomplete) view of the subject.
Thus we can view chemistry from multiple standpoints ranging from the theoretical to the eminently practical:

Mainly theoretical	Mainly practical
Why do particular combinations of atoms hold together, but not others?	What are the properties of a certain compound?
How can I predict the shape of a molecule?	How can I prepare a certain compound?
Why are some reactions slow, while others occur rapidly?	Does a certain reaction proceed to completion?
Is a certain reaction possible?	How can I determine the composition of an unknown substance?

Boiling it down to the basics

At the most fundmental level, chemistry can be organized along the lines shown here.

Dynamics

refers to the details of that rearrangements of atoms that occur during chemical change, and that strongly affect the rate at which change occurs.

Energetics

refers to the thermodynamics of chemical change, relating to the uptake or release of heat. More importantly, this aspect of chemistry controls the direction in which change occurs, and the mixture of substances that results.

Composition and structure

define the substances that are results of chemical change. Structure refers specifically to the relative arrangements of the atoms in space. The extent to which a given structure can persist is itself determined by energetics and dynamics.

 

Synthesis

strictly speaking, refers to formation of new (and usually more complex) substances from simpler ones, but in the present context we use it in the more general sense to denote the operations required to bring about chemical change and to isolate the desired products.

This view of Chemistry is a rather astringent one that is probably more appreciated by people who already know the subject than by those who are about to learn it, so we will use a somewhat expanded scheme to organize the fundamental concepts of chemical science. But if you need a single-sentence"definition of Chemistry, this one wraps it up pretty well:

Chemistry is the study of substances; their properties, structure, and the changes they undergo.

 

Micro-macro: the forest or the trees

Chemistry, like all the natural sciences, begins with the direct observation of nature— in this case, of matter. But when we look at matter in bulk, we see only the "forest", not the "trees"— the atoms and molecules of which matter is composed— whose properties ultimately determine the nature and behavior of the matter we are looking at.
This dichotomy between what we can and cannot directly see constitutes two contrasting views which run through all of chemistry, which we call macroscopic and microscopic.

• In the context of Chemistry, "microscopic" implies detail at the atomic or subatomic levels which cannot be seen directly (even with a microscope!)
• 
  The macroscopic world is the one we can know by direct observations of physical properties such as mass, volume, etc.

The following table provides a conceptual overview of Chemical science according to the macroscopic/microscopic dichotomy we have been discussing. It is of course only one of many ways of looking at the subject, but you may find it a helpful means of organizing the many facts and ideas you will encounter in your study of Chemistry. We will organize the discussion in this lesson along similar lines.

realm	macroscopic view	microscopic view
composition	formulas, mixtures	structures of solids, molecules, and atoms
properties	intensive properties of bulk matter	particle sizes, masses and interactions
change (energetics)	energetics and equilibrium	statistics of energy distribution
change (dynamics)	kinetics (rates of reactions)	mechanistics