saturated fatty acid FATTY ACIDwith a hydrocarbon
chain that contains no double bonds but has the maxi-
mum possible number of hydrogen atoms attached to
every carbon atom; it is “saturated” with hydrogen
atoms. A fatty acid is the building block of fat, which is
composed of one or more fatty acids, and exists mostly
solid at room temperature. It raises the blood LDL-
cholesterol (“bad” cholesterol) level.
saturated hydrocarbons Hydrocarbons that contain
only single carbon-carbon and carbon-hydrogen bonds.
Also referred to as alkanes or paraffin hydrocarbons.
saturated solution A solution in which no more
solute will dissolve; a solution in equilibrium with the
dissolved material. A SUPERSATURATED SOLUTIONcon-
tains more dissolved substance than a saturated solution.
scanning electron microscope A special kind of
microscope in which a finely focused beam of elec-
trons is scanned across a specimen, and the electron
intensity variations are used to construct an image of
the specimen.
scavenger A substance that reacts with (or otherwise
removes) a trace component or traps a reactive reaction
INTERMEDIATE(as in the scavenging of RADICALs or free
electrons in radiation chemistry). Also an animal that
feeds on dead animals.
Schiff base An imine bearing a hydrocarbyl group on
the nitrogen atom: R 2 C=NR′(R′≠H).
Schroedinger equation (wavefunction) Original
equation in quantum mechanics used to write wave
functions for particles; governs the evolution of proba-
bility waves in quantum mechanics.
scientific method The steps taken by a scientist after
he or she develops a hypothesis, tests its predictions
through experimentation, and then changes or discards
the hypothesis if the predictions are not supported by
the results.scientific notation The system used when studying
very small or very large quantities. A way to represent
real numbers as a number between one and 10 multi-
plied by 10 to some power, rather than in full written
form.scrambling SeeISOTOPIC SCRAMBLING.secondary alcohol An alcohol in which the OH
group is attached to a secondary carbon atom. Also
called a sec-alcohol.242 saturated fatty acid
A scientist using a scanning electron microscope (SEM). The
SEM uses a beam of electrons, rather than light, to illuminate the
subject. The wavelength of electrons is considerably shorter than
optical wavelengths, allowing a much larger magnification—up
to about 40,000×. The beam is scanned across the subject that
emits secondary electrons from its surface. These can be focused
onto a phosphor screen or detected electronically and shown on
a monitor. Nonmetallic subjects are usually coated with a thin
film of gold to reflect the beam current.(Courtesy of Chris
Taylor/CSIRO/Science Photo Library)