Why can't I have a neutral particle come into a cloud chamber and leave a track? I was reading about cloud chambers and it says when the charged particle comes in it ionizes the vapor in the chamber. But why couldn't a neutron come in and ionize the particles in the chamber with its kinetic energy? Or would the neutron have to be traveling pretty fast. Just for an approximation i set the kinetic energy of a neutron equal to the ionization energy of a hydrogen atom, and the neutron had to be going pretty fast. And also why does the alcohol vapor have to be ionized to form liquid droplets?