  We study the dynamics of the closed scalar field FRW cosmological models in
the framework of the so called Unified Dark Matter (UDM) scenario. Performing a
theoretical as well as a numerical analysis we find that there is a strong
indication of chaos in agreement with previous studies. We find that a positive
value of the spatial curvature is essential for the appearance of chaoticity,
though the Lyapunov number seems to be independent of the curvature value.
Models that are close to flat exhibit a chaotic behavior after a long time
while pure flat models do not exhibit any chaos. Moreover, we find that some of
the semiflat models in the UDM scenario exhibit similar dynamical behavior with
the Lambda cosmology despite their chaoticity.
  Finally, we compare the measured evolution of the Hubble parameter derived
from the differential ages of passively evolving galaxies with that expected in
the semiflat unified scalar field cosmology. Based on a specific set of initial
conditions we find that the UDM scalar field model matches well the
observational data.
