The surface of water can act like a sort of skin due to a property of liquids called :
Surface tension
It caused by the attraction of the particles in the surface
Hope this helps
Bohr: Electrons can jump from a path in one level to a path in another level.Electrons travel in certain paths, or energy levels
Answer: Rotation occurs at single bonds that are sigma bonds. Rotational barrier is the amount of activation energy required to covert rotamer to another by rotation that occurs around the sigma bond(C-C single bond). Due to the presence of steric hindrance that is the nonbonding interaction effects the reactivity of ions and molecules, activation energy increases. So the rotational barrier in butenyl cation is high.
