Question

A  shiny  brown  colored  element  ‘x’  on  heating  in  air  becomes  black  in  color.  Can
you  predict  the  element  ‘x’  and  the  black  colored  substance  formed?  How  do  you
support  your  prediction?

Answer 1

The shiny brown coloured element 'X' is copper and the black coloured compound formed is Copper oxide. The reaction involved is 

Answer 2

the brown coloured element is copper. by the experiment of oxidation we will observe black color copper oxide.
prediction:
cu+02=>2Cuo
CuO+H2=>Cu+H2O
this is in the presence of heat