What is impulse? how does this relate to momentum?

Impulse is a force acting briefly on a body and producing a finite change of momentum.
This relates to momentum because impulse is a change in momentum. Impulse = momentum. Since force is a vector quantity, impulse is also a vector in the same direction. Impulse applied to an object produces equivalent vector change in its linear momentum, also in the same direction. m•(triangle)v

A. they hold atoms  together with a molecule.its a force that exist between molecules. hope this .