We measure the expansion of the forward shock of the Small Magellanic Cloud 
supernova remnant 1E 0102.2-7219 in X-rays using Chandra X-Ray Observatory 
on-axis Advanced CCD Imaging Spectrometer (ACIS) observations from 1999--2016. 
We estimate an expansion rate of 0.025+/-0.006 %/yr and a blast-wave velocity 
of 1,617+/-367 km/s. This velocity implies a lower limit on the postshock 
electron temperature of ~1.10 keV differing significantly from an estimate of 
0.52+/-0.06 keV based on the X-ray spectral analysis. This indicates that 
some shock energy may have gone into accelerating cosmic rays. We combine the 
expansion rate with the blast wave and reverse shock radii to generate a grid 
of one-dimensional models for a range of ejecta masses (2-6 mdot) to 
constrain the explosion energy, age, circumstellar density, swept-up mass, 
and unshocked ejecta mass. We find acceptable solutions for a constant 
density ambient medium and for an r^{-2} power-law profile (appropriate for a 
constant progenitor stellar wind). For the constant density case, we find an 
age of ~1800 yr, explosion energies of 0.87-2.61e51 erg, ambient densities of 
0.85-2.54 cm^-3, swept-up masses of 22-66 mdot, and unshocked ejecta masses 
of 0.05-0.16 mdot. For the power-law density profile case, we find an age of 
~2700~yr, explosion energies of 0.34-1.02e51 erg, densities of 
0.22-0.66 cm^{-3} at the blast wave, swept-up masses of 17-52 mdot, and 
unshocked ejecta masses of 0.06-0.18 mdot. Assuming the true explosion 
energy was 0.5-1.0e51 erg, ejecta masses 2-4 mdot are favored for the 
constant density case and 4-6 mdot for the power-law case. The estimates 
for unshocked ejecta mass are comparable to the mass of Fe expected in 
core-collapse supernovae with progenitor mass 15.0-40.0 mdot, offering a 
possible explanation for the lack of Fe emission observed in X-rays.