subtract the mass of the filter paper (0.27g) from the mass on f the paper and copper (0.98g). record the difference in the data table as the amount that of copper

Is a logical series of steps

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   

Ibelieve the answer is weathering,hope my answer has you : )