What is the difference between mechanical digestion and chemic al digestion in the mouth?

Well mechanical digestion involves physically  breaking the food into smaller pieces but chemical digestion involves breaking down into simpler nutrients that can be used by cells.

Mechanical digestion occurs with mastication between teeth and the maneuvering of food into a bolus by the tongue. chemical digestion refers to digestive enzymes secreted in the saliva such as amylase which helps in breaking down protein into smaller subunits.