Question

Brown coloured copper powder on heating in air turns into black and coloured substance

Answer 1

On heating copper powder in air the surface of copper powder become coated with black copper oxide which is black in colour

following reaction occurs -
2Cu +O2= 2CuO

Answer 2

$\huge \bold {\underline \red{A}}\bold {\underline \orange{n}}\bold {\underline \purple{s}}\bold {\underline \pink{w}}\bold {\underline \green{e}}\bold {\underline \blue{r}} \bold { \red{ - }}$

This black substance formed on the surface is because of the process called surface oxidation. Upon heating, the copper metal melts gradually and turns black on the surface. This is because the copper powder present in the china dish reacts with the atmospheric oxygen and forms copper (II) oxide.