The anti-conformation is the most stable conformation of n-butane. In this, the bulky methyl groups are as far apart as possible thereby keeping steric repulsion at a minimum.

On cracking or pyrolysis, the hydrocarbon with higher molecular mass gives a mixture of hydrocarbons having lower molecular masses. Hence, liquid hydrocarbons can be converted into a mixture of gaseous hydrocarbons. (Lower hydrocarbons exist in gaseous state while higher ones are in liquid state or solid state.)

$$ \therefore $$ C₂ - sp, C₃ - sp³, C₅ - sp² and C₆ - sp³

Alkenes with double bonds cannot undergo free rotation and can have different geometrical shapes with two different groups on each end of the double bond.