  Spectral energy distributions are presented for 94 young stars surrounded by
disks in the Serpens Molecular Cloud, based on photometry and Spitzer IRS
spectra. Taking a distance to the cloud of 415 pc rather than 259 pc, the
distribution of ages is shifted to lower values, in the 1-3 Myr range, with a
tail up to 10 Myr. The mass distribution spans 0.2-1.2 Msun, with median mass
of 0.7 Msun. The distribution of fractional disk luminosities in Serpens
resembles that of the young Taurus Molecular Cloud, with most disks consistent
with optically thick, passively irradiated disks in a variety of disk
geometries (Ldisk/Lstar ~ 0.1). In contrast, the distributions for the older
Upper Scorpius and Eta Chamaeleontis clusters are dominated by optically thin
lower luminosity disks (Ldisk/Lstar ~ 0.02). This evolution in fractional disk
luminosities is concurrent with that of disk fractions. The actively accreting
and non-accreting stars (based on Ha data) in Serpens show very similar
distributions in fractional disk luminosities, differing only in the brighter
tail dominated by strongly accreting stars. In contrast with a sample of Herbig
Ae/Be stars, the T Tauri stars in Serpens do not have a clear separation in
fractional disk luminosities for different disk geometries: both flared and
flat disks present wider, overlapping distributions. This result is consistent
with previous suggestions of a faster evolution for disks around Herbig Ae/Be
stars. Furthermore, the results for the mineralogy of the dust in the disk
surface do not show any correlation to either stellar and disk characteristics
or mean cluster age in the 1-10 Myr range probed here. A possible explanation
for the lack of correlation is that the processes affecting the dust within
disks have short timescales, happening repeatedly, making it difficult to
distinguish long lasting evolutionary effects. [abridged]
