Illustrate how copper metal can give different products on reaction with `HNO_(3)`.

Explanation

On heating with dil `HNO_(3)`, copper nitrate and nitric oxide.
`3Cu + 8HNO_(3) ("dil") overset("Heat")rarr 3Cu (NO_(3))_(2) + 4H_(2)O + 2NO` (nitric oxide)
With conc. `HNO_(3)` instead of `NO, NO_(2)` is evolved
`Cu + 4HNO_(3) ("conc.") overset("Heat")rarr Cu(NO_(3))_(2) + 2H_(2)O + 2NO_(2)` (nitrogen dioxide)