Students may have a familiarity with the colors assigned to
particular elements from the use of molecular modeling kits. All
modeling kits use the CPK coloring system (designed by
chemists Robert Corey and Linus Pauling, and improved by
Walter Koltun).16 Pipe cleaners are available in most of the
CPK colors. Figure 7 shows some models made using pipe
cleaners with CPK colors. This increases the cost of the activity
(as packs of single color pipe cleaners are more expensive than
mixed packs); however, it is a useful approach to produce
models analogous to those constructed with 3D molecular
models, especially with older students, and can help the
modeling process “feel” more familiar.