what is conformations of alkanes like ethane etc?
Conformations , various forms of molecule are related by very simple rotation around a single bond. These kind of inter conversions are generally very fast, because of that sample of a molecule can exist in many different conformations.
For alkanes, many conformations can be shown by using the dash-wedge notation in structural drawing. An alternative approach is Newman Projection, which view molecule by looking a C-C bond axis.