Why loss of mass is a apparent loss?

Lewis structure and molecular geometry for nh2cl

Arollercoaster car at the top of a hill has potential energy kinetic energy chemical energy light energy

Which of the following observations indicates that there is a small, dense, positively charged part in the center of an atom? some uncharged particles are scattered by a gold foil. all uncharged particles are attracted towards a gold foil. all positively charged particles pass straight through a gold foil. some positively charged particles bounce back from a gold foil.