During the AIChE conference last month, and during many such conferences, the question of what is it to "do" chemical engineering arises. I've always liked to think of it as using chemistry, math, physics to develop salable goods and services. Even this doesn't fit all people who do chemical engineering.
Traditional chemical engineering (if there ever was such a thing) landed people in petrochemical companies, where we built refineries and chemical production facilities that produced millions of pounds a day (DuPont, Dow, Shell, Exxon, etc.). That's where my father spent many years of his life as a chemical engineer, until the research center shifted to biosciences and agricultural chemicals and now to pharmaceutical contract manufacture. Research under the guise of chemical engineering covers everything from beer and cereal to pharmaceuticals (both the substance and the product) to medical products to nanomaterials to, yes, the petrochemical industry. That is only one way to slice it. Chemical engineers also tend to apply specific techniques across all of these industries: types of analysis, computational modeling, process control, process synthesis. The WWW Virtual Library on Chemical Engineering lists 30 different subtopics of chemical engineering.
We end up needing to know a lot (education) because we end up in so many different areas of industry. This frequently makes our discussions sound like we "know it all," much to the detriment of good relationships with our business colleagues in chemistry, biology, finance, and other fields. We cannot possibly know it all any more than other people.
This all becomes an issue when the American Institute of Chemical Engineers needs to define itself and its mission to its members. It has has some troubles lately with the economic uncertainties. During a conversation on how The Institute is using technology, the ideas ranged all over the place, but I never understood how this was going to serve the organization or the people that AIChE represents. Fun.
Here are some definitions, if you are curious:
Web WordNet
History of ChEn
US Dept of Labor, Bureau of Labor Statistics description