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Nitric Acid Acts Upon Copper (5 Favorites)

DEMONSTRATION in Observations, Chemical Change, History, Reduction, Redox Reaction, Oxidation. Last updated July 23, 2021.


Summary

In this demonstration, students will hear a story about how Ira Remsen’s interest in chemistry was sparked and watch a demonstration that recreates her first experiment reacting nitric acid with a copper penny.

Grade Level

High school

NGSS Alignment 

This demonstration will help prepare your students to meet the performance expectations in the following standards:

  • HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties. 
  • Scientific and Engineering Practices:
    • Constructing Explanations and Designing Solutions
    • Engaging in Argument from Evidence

Objectives

By the end of this demonstration, students should be able to

  • Explain how Ira Remsen’s interest in chemistry was sparked.
  • Explain the steps in the reaction between copper and nitric acid.

Chemistry Topics

This demonstration supports students’ understanding of

  • History of Chemistry
  • Chemical Changes
  • Redox Reaction
  • Observations

Time

Teacher Preparation: 1 hour

Lesson: 20 minutes

Materials

  • Concentrated nitric acid, 15.8 M
  • 1-L Erlenmeyer flask
  • One-hole stopper that fits on the Erlenmeyer flask
  • Polished glass tubing that fits into the hole stopper
  • Clear plastic hose that fits over the glass tubing
  • Piece of copper
  • 2-L beaker
  • Fume hood
  • 2-L Beaker
  • Water
  • Optional: Universal Indicator solution (see note below)

Safety

  • This experiment should be done in a fume hood, as toxic gas is released.
  • Wear an apron, gloves, and safety goggles while performing the demonstration.
  • Take extreme care when handling concentrated nitric acid.

Teacher Notes

  • If you do not have a fume hood, you can use this video of the demonstration. Turn down the volume so that you can read Ira Remsen’s journal entry as the video plays. The script for the journal entry and demo is included in the procedures below. 
  • Please read through all the demonstration procedures and notes, regardless if you do the demo live or use the video.
  • Further explanation of the chemistry of this demonstration can be found in the article, Ira Remsen: Stories for Chemical Education, from the Royal Australian Chemical Institute. 
  • This is an excellent demonstration to start the school year. It is visually appealing to students and offers many observations that can be referred to as you teach different concepts throughout the year: solutions, chemical reactions and equations, reaction types and redox reactions, energy and thermodynamics, gas laws and solutions.
  • Have students take detailed notes of their observations so that they can refer to them during later lessons.
  • This demonstration can be extended by having students write out the chemical reactions that are taking place.  Cu (s) + 4 HNO3 (aq)  Cu(NO3)2 (aq) + 2 NO2 (g) + 2 H2O (l)
  • If you do the demo live and collect the nitrogen dioxide gas under water, you can discuss a second equation, shown below. The reaction between the nitrogen dioxide gas (which is brown) and water produces nitric acid and nitrogen monoxide gas (which is colorless). The brown gas becomes colorless as it travels through the tube to the beaker of water.

3NO2 (g) + H2O (l) → 2HNO3 (aq) + NO (g)

  • As the concentrated copper (II) nitrate in the flask cools, water from the beaker is drawn to the flask, diluting the solution, which then turns the solution from green to blue. The remaining brown gas also reacts with the water and the gas becomes colorless.
  • If you want to shorten the demo you can stop after the brown gas travels to the beaker of water, not waiting to have the water move through the tube to the flask. If using the video, stop it once the water starts moving through the tube and fast forward to the color changes when the water enters the flask.
  • If you choose to use the Universal Indicator solution in the water students will see a color change as the nitrogen dioxide reacts with the water to form an acid.

Demonstration:

  • Purpose: This demonstration can be used to start off the year, sparking student interest in chemistry and a desire to learn an explanation for all of the things that happened before their eyes.  This demonstration will produce two reactions, one between the copper and nitric acid and the other between nitrogen dioxide and water.
  • Preparation: 
    • Secure a short piece of polished glass tubing through a one-hole stopper.  
    • Fit the stopper into the top of a one-liter Erlenmeyer flask.  
    • If you’d like to add an acid-base component to the demonstration, add Universal Indicator to the water. 
    • Attach one end of a length of clear plastic hose to the glass tubing and place the other end in a 2-L beaker that is filled with water.  
    • Cut a 2-cm square of copper. It will represent Remsen’s penny. If you can find some pre-1983 pennies you can use them instead. 
    • Have 50 mL of concentrated nitric acid available. This should be placed in your fume hood.  
    • Wear an apron, gloves, and safety goggles while performing the demonstration.
  • Procedure
    • Read the following story by Ira Remsen, who discovered saccharin and founded the department of chemistry at Johns Hopkins University, as you are performing this demonstration: While reading a textbook of chemistry I came upon the statement, "nitric acid acts upon copper." I was getting tired of reading such absurd stuff and I was determined to see what this meant. Copper was more or less familiar to me, for copper cents were then in use. I had seen a bottle marked nitric acid on a table in the doctor's office where I was then "doing time." I did not know its peculiarities, but the spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words "act upon" meant. The statement "nitric acid acts upon copper" would be more than mere words. 
    • Hold up the nitric acid and copper when they are mentioned.  Place the copper or penny in the flask.  Continue reading the autobiography: All was still. In the interest of knowledge I was even willing to sacrifice one of the few copper cents then in my possession. I put one of them on the table, opened the bottle marked nitric acid, poured some of the liquid on the copper, and prepared to make an observation. But what was this wonderful thing which I beheld? The cent was already changed and it was no small change either. A green-blue liquid foamed and fumed over the cent and over the table. The air in the neighborhood of the performance became colored dark red. A great colored cloud arose. This was disagreeable and suffocating. How should I stop this?
    • Pour the nitric acid into the flask after reading the second sentence and quickly tighten the stopper. Continue to slowly read the autobiography as the reaction occurs: I tried to get rid of the objectionable mess by picking it up and throwing it out of the window. I learned another fact. Nitric acid not only acts upon copper, but it acts upon fingers. The pain led to another unpremeditated experiment. I drew my fingers across my trousers and another fact was discovered. Nitric acid acts upon trousers. Taking everything into consideration, that was the most impressive experiment and relatively probably the most costly experiment I have ever performed... It was a revelation to me. It resulted in a desire on my part to learn more about that remarkable kind of action. Plainly, the only way to learn about it was to see its results, to experiment, to work in a laboratory.
    • Point out that the reaction vessel is hot to the touch.
    • Point out how the brown gas “disappeared” as it bubbled through the water and discuss the second reaction. As the copper (II) nitrate cools, water will be drawn into the flask, diluting the solution and reacting with the gas.

For the Student

Lesson

Background

Ira Remsen was a famous chemist who founded the Johns Hopkins University chemistry department and an early laboratory for chemical research in the United States. While he was studying chemistry, he made an “accidental” discovery about the importance of doing and experiencing science, instead of just reading about it. The demonstration you will see today is based on one of his early journal entries about an amazing discovery he made in the lab.

Purpose

To make careful observations about chemical reactions.

Instructions

As you watch the demonstration, make careful observations about the two reactions you will see. We will refer to these reactions and observations as we move through the school year.

Reaction 1: Copper (a penny) reacts with nitric acid solution, producing copper (II) nitrate solution, nitrogen dioxide gas, and liquid water:

Cu (s) + 4 HNO3 (aq) → Cu(NO3)2 (aq) + 2 NO2 (g) + 2 H2O (l)

  1. Describe the solid copper and the nitric acid solution before the reaction.
  2. Make observations that might indicate that a reaction might be occurring.
  3. Based on your observations, which product was the nitrogen dioxide and which was the copper (II) nitrate? How do you know?
  4. The reaction flasks “feels hot to the touch”. Do you think that the reaction produced or absorbed energy (heat) and explain your answer.

The brown gas that is produced in the first reaction collects in the flask and then travels into the beaker of water and seems to disappear. The water changed color, indicating that it was becoming acidic.

Reaction 2: Nitrogen dioxide gas (brown) reacts with liquid water and produces nitric acid solution and nitrogen monoxide gas (colorless).

NO2 (g) + H2O (l) HNO3 (aq) + NO (g)

  1. Describe the nitrogen dioxide gas and liquid water before the reaction.
  2. Make observations that might indicate that a reaction might be occurring.
  3. Can you explain the color change?

As the flask containing the brown nitrogen dioxide gas and copper (II) nitrate solution cools, the water in the beaker is drawn through the tube and into the flask.
The solution is diluted and changes colors and the brown gas seems to disappear.

  1. Describe the color change in the solution.
  2. What do you think happened to the brown gas?