When Copper is heated with $\mathrm{Conc}.{\mathrm{HNO}}_3$, it produces-

Redox reactions:

• “The reactions in which both oxidation and reduction take place are called oxidation-reduction reactions or redox reactions.”

Reaction of Copper with $\mathrm{Conc}.{\mathrm{HNO}}_3$:

• The reaction of Copper ($\mathrm{Cu}$) with concentrated nitric acid $\left({\mathrm{HNO}}_3\right)$ produces Cupric nitrate ($\mathrm{Cu}({\mathrm{NO}}_3{)}_2$), and Nitrogen dioxide (${\mathrm{NO}}_2$) along with water.
• Nitric acid (${\mathrm{HNO}}_3$) is a strong oxidizing agent that oxidizes Copper ($\mathrm{Cu}$) while itself gets reduced.
• The reaction is as follows:

$\underset{\left(\mathrm{Copper}\right)}{\mathrm{Cu}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Nitric}\mathrm{acid}\right)}{4{\mathrm{HNO}}_3\left(\mathrm{aq}\right)}\to \underset{\left(\mathrm{Cupric}\mathrm{nitrate}\right)}{\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)}+\underset{\left(\mathrm{Nitrogen}\mathrm{dioxide}\right)}{2{\mathrm{NO}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$