Why do atoms move at different speeds depending on whether they are in liquids or solids.

In a solid the atoms are tightly packed together and vibrate in place, in a liquid the atoms are loosely packed together and can move past each other,
 
extra: and in a gas the atoms are far apart and move freely and 

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf   

Idk the answer imthink snail cant mate they dont lol