Answer:
The reaction that occurs is a redox reaction. The Copper metal (Cu 0)on the copper pennies is oxidized in concentrated nitric acid to produce Cu2+ ions. Copper is easily oxidized to Cu2+, which is blue in aqueous solutions (water) so you should see the solution turn blue as the copper penny reacts.
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Taking into account the definition of chemical and physical change, the reaction of the copper penny with nitric acid is a chemical change.
Physical changes are those in which the substances involved are the same before and after the change. That is, a physical change is a transformation in which the nature of matter does not change.
Chemical changes are considered to be those in which the substances involved are transformed into totally different ones.
In this way, the initial substances do not exist after the phenomenon has occurred and instead, new substances are formed, different from the initial ones.
That is, a chemical change is a transformation in which the nature of matter varies.
When a penny of copper reacts with nitric acid, a redox reaction occurs where the copper metal in the copper pennies is oxidized to produce Cu²⁺ ions, whereas because the nitric acid oxidizes the copper, the nitric acid itself is reduced to nitric oxide (NO). Nitric oxide then reacts with oxygen in the air to produce nitrogen dioxide (NO₂). This can be represented by:
Cu + 4 HNO₃ → Cu²⁺(ac) + 2 NO₃⁻ + 2 NO₂ + 2 H₂O
Finally, the reaction of the copper penny with nitric acid is a chemical change because a redox reaction occurs.
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