The properties of an average conformation are not always the same as the average of the properties for the individual conformations. This is particularly relevant when the properties are not linearly dependent on the conformation. They can be used to deduce the conformation of a molecule but as you can see, care must be taken in their calculation. This ability means that MD is a deterministic method . Molecular Dynamics Simulation Molecules are dynamic.
All molecules are in motion except at absolute zero.
The motion can be associated with overall translation, rotation or vibration, which are relevant to temperature and pressure of a system. However, more importantly, some of the motions are internal. These internal motions can drastically alter the conformation of the molecule, particularly through torsion rotation. In reality, one conformational state changes to another in a smooth time-dependent manner. This is an infinite series and must at some point be truncated.