When we rub our hands, they become warm. Have we supplied heat to the hands?

A force F is applied on a block of mass M. the block is displaced through a distance d in the direction of the force. What is the work done by the force on the block? Does the internal energy change because of this work?

The outer surface of a cylinder containing gas is rubbed vigorously by a polishing machine. The cylinder and its gas become warm. Is the energy transferred to the gas heat or work?

A closed bottle contains some liquid. The bottle is shaken vigorously for 5 minutes. It is found that the temperature of the liquid is increased. Is heat transferred to the liquid? Is work done on the liquid? Neglect expansion on heating.

The final volume of a system is equal to the initial volume in a certain process. Is the work done by the system necessarily zero? Is it necessarily nonzero?