The term for free electrons in metals transferring energy by colliding with other atoms or electrons is

Conduction

In metals, the electrons of each atom are delocalized, which means they are free to move about in the structure of the metal. When heat is applied at one end of the metal, the electrons there are excited and collide with surrounding particles, transferring their energy to them. This is what makes metals very good conductors of both heat and electricity. 

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.