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Copper and Nitric Acid Chemistry Demonstration

The copper and nitric acid reaction is a dramatic color change chemistry demonstration. The reaction illustrates several chemistry principles, including exothermic reactions , redox reactions , coordination complexes, oxidation, oxidation states , and the metal activity series . Here are instructions explaining how you perform this demonstration safely, with a look at its chemical reactions.

You only need two common chemicals. The most important part of the reaction is the choice of reaction vessel. The reaction produces heat, so use a study glass container.

• 40 ml concentrated nitric acid (HNO 3 )
• 1-liter flask (Erlenmeyer, boiling flask, or Buchner flask)
• Clamp stand
• Bowl (optional)

The original demonstration uses a copper penny, but modern pennies are zinc plated with a thin layer of copper. A better choice is a piece of copper wool or some copper shavings. The reaction works fine with copper wire, but is not as dramatic because the wire has less surface area.

A smaller version of the demonstration uses a bit of copper, a small volume of nitric acid, and a borosilicate glass test tube.

Perform the Copper and Nitric Acid Chemistry Demonstration

Nothing could be easier! Set up and perform the demonstration inside a fume hood.

• Pour the nitric acid into the flask.
• When you are ready for the reaction, add the copper.

Initially, the nitric acid attacks the copper, turning the liquid green and releasing heat and reddish brown nitrogen dioxide vapor. Eventually, even the liquid turns brown.

• Add water and dilute the solution.

Diluting the acid changes the conditions. The liquid changes color into a bright blue, while the vapor changes from reddish brown to colorless.

A Look at the Chemistry

If you look at the metal reactivity series, copper is pretty unreactive. It’s even considered a noble metal by some chemists. It resists oxidation by hydrochloric acid (HCl), yet readily reacts with nitric acid (HNO 3 ). This is because nitric acid acts both as an oxidizer and an acid. Copper reacts with nitric acid, forming aqueous copper nitrate, nitrogen dioxide gas, and water.

Cu(s) + 4HNO 3 (aq) → Cu(NO 3 ) 2 (aq) + 2NO 2 (g) + 2H 2 O(l)

The reaction immediately produces heat (reaching 60 to 70 degrees C) and releases deeply-colored nitrogen dioxide gas. The green color comes from copper(II) ions forming a coordination complex with nitrate ions. Diluting the concentrated acid with water changes the liquid color to blue as the water displaces the nitrate ions, leaving only aqueous copper(II) nitrate. The water reacts with nitrogen dioxide and forms nitric oxide.

3Cu(s) + 8HNO 3 (aq) → 3Cu 2+ (aq) + 2NO(g) + 4H 2 O(l)+ 6NO 3 − (aq)

The concentration of the acid affects its oxidizing capacity. For example, copper does not react with dilute sulfuric acid (H 2 SO 4 ), but a similar reaction occurs in concentrated sulfuric acid:

Cu + 2H 2 SO 4  → SO 2  + 2H 2 O + SO 4 2−  + Cu 2+

Containing the Copper and Nitric Acid Reaction

A few simple revisions contain the reaction and improve both the safety and dramatic effect of the copper and nitric acid chemistry demonstration. You can perform this variation of the copper and nitric acid reaction out in the open, but it’s still a good idea to separate the set-up from the audience using a safety shield.

• Add nitric acid to a round-bottomed borosilicate flask. Clamp it into position on a stand. Ideally, use a borosilicate flask and place a bowl beneath the flask in case the glass leaks or breaks.
• Fill an Erlenmeyer (conical) flask with water and clamp it into position near the round flask.
• Stopper the round flask (acid) and loosely plug the conical flask with glass wool. The glass wool prevents the escape of nitrogen dioxide into the outside air. Insert glass tubing the ends reach the bottoms of each flask. (Don’t use plastic tubing.)
• When you are ready for the demonstration, add the copper to the borosilicate flask and fit the stopper and tube onto it.

Initially, the liquid in the round flask turns green and evolves reddish brown nitrogen dioxide. After about a minute and a half, the reaction slows and cools. The pressure reduction from the cooling draws water in from the conical flask. This dilutes the nitric acid and also reacts with the nitrogen dioxide gas, forming a fountain. Finally, the liquid in the round flask turns blue as copper nitrate forms.

Safety and Disposal

• Only perform this demonstration if you are a chemist or chemistry educator and have access to proper safety gear and a fume hood. Nitric acid is a corrosive strong acid, while nitrogen dioxide is a toxic reddish-brown gas. Wear gloves, goggles, and a lab coat. Perform the open demonstration under a fume hood.
• Please choose sturdy glassware for this demonstration. The initial reaction produces heat, so there is a risk of glassware breakage. For this reason, a boiling flask is ideal. Alternatively, use a Buchner flask.
• After the demonstration, neutralize the dilute nitric acid using any inorganic base, such a baking soda, sodium hydroxide solution, or potassium hydroxide solution. The neutralization reaction also produces some heat. Afterward, you can safely wash the liquids down the drain with water.
• Cotton, F. Albert; Wilkinson, Geoffrey (1988). Advanced Inorganic Chemistry (5th ed.). New York: John Wiley & Sons. 769-881.
• Shakhashiri, Bassam Z. (1985). “Properties of Nitrogen(II) Oxide”. Chemical Demonstrations: A Handbook for Teachers of Chemistry Volume 2 . The University of Wisconsin Press. ISBN: 978-0299101305.
• Shakhashiri, Bassam Z. (1985). “Coin-Operated Red, White, and Blue Demonstration: Fountain Effect With Nitric Acid and Copper”. Chemical Demonstrations: A Handbook for Teachers of Chemistry Volume 3 . The University of Wisconsin Press. 83-91. ISBN: 978-0299119508.
• Summerlin, Lee R.; Borgford, Christie L., Ealy, Julie B. (1988 ). Chemical Demonstrations: A Sourcebook for Teachers Volume 2 (2nd ed.). American Chemical Society. ISBN: 978-0841215351.

Electroplating: Copper-Plated Key

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Electroplating uses a form of electrolysis in which the electrodes play a bigger role than just conducting the current.

Using electricity, you can coat the metal of one electrode with the metal of the other in an electroplating process, also known as electrochemistry.

Electroplating, also known as electrodeposition, is essentially a chemical reaction that helps to make various items we see and use every day. There are also specific types of electroplating such as copper plating, silver plating, and chromium plating. Jewelry and silverware can be silver- or gold-plated, while zinc is often used to coat iron to protect against corrosion. Professional electroplating requires specialized chemicals and equipment to make a high-quality coat, but in this project, you can try your hand at a simple procedure that will transfer copper (a versatile, naturally occurring metal ) to a brass key.

Being red in color, copper is known for its high electrical conductivity, malleability, and corrosion resistance. In copper electroplating, a metal substrate is placed in an electrolytic bath and an electric current is used to cause copper ions to adhere to the base material's surface.

(Adult supervision and chemical safety equipment required.)

Watch us use electricity to copper-plate a brass key (copper electroplating) in this Home Science Tools video. See this project in action!

What You Need:

• 1.5-volt D battery with the battery holder (for power supply)
• Two alligator clip leads or insulated wire
• Beaker or glass (250-ml beaker is recommended or similar glass size)
• Copper strip (pure copper)
• Copper sulfate  
• Copper electrode (or coil of copper wire)
• Safety equipment

How to Electroplate Copper:

• Prepare the key for the DIY copper plating by cleaning it with a thin layer of toothpaste or soap and water. Dry it off on a paper towel.
• Stir copper sulfate into some hot water in a beaker until no more will dissolve. Your solution should be dark blue. Let it cool.
• Use one alligator clip and attach the copper electrode to the positive terminal of the battery (this is now the anode ) and then attach the key to the negative terminal (now called the cathode ).
• Partially suspend the key in the solution by wrapping the wire lead loosely around a pencil and place the pencil across the mouth of the beaker. The alligator clip should not touch the solution.
• Place the copper strip/mass of copper into the solution, making sure it doesn't touch the key. The plating solution level is now below the alligator clip. The copper strip will produce a path for conductivity. An electrical circuit has now formed with the positive electrodes & negative electrodes and an electrical current is flowing.
• Leave the circuit running for 20-30 minutes, or until you are happy with the amount of copper on the key.

What Happened During the Plating Process:

The copper sulfate solution is an electrolyte solution that conducts electricity from one electrode to the other, creating an electrical current.

When the current is flowing, oxidation (loss of electrons) happens at the copper anode, adding copper ions to the solution.

Those ions travel on the electric current to the cathode, where reduction (gain of electrons) happens, plating the copper ions onto the key.

There were already copper ions present in the copper sulfate solution before you started, but the oxidation reaction at the anode kept replacing them in the solution as they were plated with a thin layer onto the key, keeping the reaction going.

This project has many variables, including the cleanness and smoothness of the key, the strength of the copper sulfate solution, and the strength of the current.

If a black soot-like substance starts forming on the key, your solution is not strong enough for the current. Take the electrodes out and add more copper sulfate. When you put them back in, make sure the anode and cathode are as far apart as possible. Be sure to take notes for your science experiment to ensure you have great data collection.

There are lots of projects you can do with electroplating!

One fun idea is to use a flat piece of brass as your cathode and draw a design on it with an oil-based marker. The copper will not bond where the marker is.

After you're done plating it, you can use acetone (or nail polish remover) to wipe off the marker, leaving a design of the brass showing through the copper. Copper is relatively dull in color, which means other additives may be needed if a brighter finish is required. You can use a little metal polish to make the copper shiny if you desire.

You may want to try this simple copper-plating experiment that doesn't use electrolysis and requires only household materials.

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Copper chemistry in action.

Please read all the instructions before you begin and record your results throughout the experiment. Then compare your results with a friend!

• 10 dirty pennies
• 4 tablespoons lemon juice
• 8 tablespoons vinegar
• 1 teaspoon salt
• small bowl (not metal!)
• 1 spoon (not metal!)
• paper towels or napkins

Instructions

• Mix the lemon juice, vinegar and salt in the bowl until dissolved.
• Take a penny and dip it half way into the mixture for 20 seconds. Take it out - what happened?
• Put the rest of the pennies into the mixture. Watch carefully. What happens?
• In 5 minutes, take 4 of the pennies out and lay them on a paper towel to dry.
• Take the remaining pennies out of the mixture and hold them under running water until they are thoroughly rinsed. Lay them out to dry on another paper towel and label them "clean."

What Happened?

Why did the pennies look dirty when you started the experiment.

Chemistry can answer these questions! Do you know what an atom is? Atoms are microscopically tiny particles that are the basic building blocks of virtually everything we can see. Our bodies are made up of billions and billions of atoms - all different shapes and sizes. But some things are made up of only one kind of atom. For example, the copper used for pennies is made up mainly of copper atoms. But when they join with other atoms, like oxygen in the air, they form molecules - in this case a molecule called copper oxide. The copper oxide makes the pennies look dirty.

Why does the mixture clean the pennies?

The mixture is acidic, and the acid from the lemon juice and vinegar dissolves the copper oxide. Why not try to dissolve copper oxide in other acidic mixtures! What can you think of?

The pennies that weren't rinsed turned a blue color. Why?

When the mixture removes the copper oxide, it becomes easy for the copper atoms to join together with oxygen and chlorine (salt). When this happens, a new compound is formed, called malachite. Malachite is usually blue-green.

Metal Plating Experiment - Teach Kids about Copper Ions

Posted by Admin / in Chemistry Experiments

Pennies that look dull and are no longer shiny can be cleaned and in the process the copper can be used to provide a shiny copper coating to a nail. Pennies that are dull have experienced oxidation in the form of a copper-oxygen compound which has formed on the surface. A natural acid can be used to remove the dull oxidized surface. The natural acid is then used to transfer the copper to the surface of an iron nail.

Items Needed for Experiment

• 20 dirty pennies
• disposable cup
• steel wool or sandpaper
• 2 iron nails (not galvanized)
• work gloves

EXPERIMENT STEPS

Step 1: Pour about two inches of lemon juice in the bottom of a disposable cup.

Step 2: Place the dirty pennies in the bottom of the cup containing the lemon juice. Non-war time pennies that were minted before 1982 have much more copper content than newer pennies. New pennies only have a thin plating of copper. The remaining metal is actually zinc.

Step 3: Add a pinch of salt to the lemon and penny mixture..

Step 4: Take one iron nail and rub it with steel wool or fine sandpaper. If using steel wool, use the work gloves and be careful not to touch the steel wool to avoid getting any of the thin steel wool pieces in your skin. Set the other iron nail aside.

Step 5: Place the iron nail in the lemon/salt/penny mixture and let the pennies sit about an hour.

Step 6: Pour the lemon juice down the drain, leaving the pennies and nail behind. Never drink the lemon juice used in this experiment. The residual liquid left in the juice can make you sick. Throw away the cup after using it for the experiment also.

Step 7: Look at the nail. Compare this nail to the nail that was not placed in the lemon/copper solution. What do you see? Is any copper plating now on the nail?

SCIENCE LEARNED

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Douglas Rogers - Douglas is a professional engineer and supports math and science education for kids.

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10 Cool Chemistry Experiments

ThoughtCo / Hilary Allison

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• Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
• B.A., Physics and Mathematics, Hastings College

Chemistry is king when it comes to making science cool. There are many interesting and fun projects to try, but these 10 chemistry experiments might be the coolest.

Whether you want to witness color transformations with copper and nitric acid or create a foam spectacle with hydrogen peroxide and potassium iodide, there's something here to spark curiosity in everyone. There's even a famous chemical reaction that will emit blue light and a characteristic barking or woofing sound.

Copper and Nitric Acid

When you place a piece of copper in nitric acid , the Cu 2+ ions and nitrate ions coordinate to color the solution green and then brownish-green. If you dilute the solution, water displaces nitrate ions around the copper, and the solution changes to blue.

Hydrogen Peroxide with Potassium Iodide

Affectionately known as elephant toothpaste , the chemical reaction between peroxide and potassium iodide shoots out a column of foam. If you add food coloring, you can customize the "toothpaste" for holiday-colored themes.

Any Alkali Metal in Water

Any of the alkali metals will react vigorously in water . How vigorously? Sodium burns bright yellow. Potassium burns violet. Lithium burns red. Cesium explodes. Experiment by moving down the alkali metals group of the periodic table. 

Thermite Reaction

The thermite reaction essentially shows what would happen if iron rusted instantly, rather than over time. In other words, it's making metal burn. If the conditions are right, just about any metal will burn. However, the reaction usually is performed by reacting iron oxide with aluminum:

Fe 2 O 3  + 2Al → 2Fe + Al 2 O 3  + heat and light

If you want a truly stunning display, try placing the mixture inside a block of dry ice and then lighting the mixture.

Coloring Fire

 SEAN GLADWELL / Getty Images

When ions are heated in a flame, electrons become excited and then drop to a lower energy state, emitting photons. The energy of the photons is characteristic of the chemical and corresponds to specific flame colors . It's the basis for the flame test in analytical chemistry , plus it's fun to experiment with different chemicals to see what colors they produce in a fire.

Make Polymer Bouncy Balls

Who doesn't enjoy playing with bouncy balls ? The chemical reaction used to make the balls makes a terrific experiment because you can alter the properties of the balls by changing the ratio of the ingredients.

Make a Lichtenberg Figure

A Lichtenberg figure or "electrical tree" is a record of the path taken by electrons during an electrostatic discharge. It's basically frozen lightning. There are several ways you can make an electrical tree.

Experiment with 'Hot Ice'

Hot ice is a name given to sodium acetate, a chemical you can make by reacting vinegar and baking soda. A solution of sodium acetate can be supercooled​ so that it will crystallize on command. Heat is evolved when the crystals form, so although it resembles water ice, it's hot.

Barking Dog Experiment

The Barking Dog is the name given to a chemiluminescent reaction involving the exothermic combination of either nitrous oxide or nitrogen monoxide with carbon disulfide. The reaction proceeds down a tube, emitting blue light and a characteristic "woof" sound.

Another version of the demonstration involves coating the inside of a clear jug with alcohol and igniting the vapor. The  flame front proceeds down the ​bottle , which also barks.

Dehydration of Sugar

When you react sugar with sulfuric acid , the sugar is violently dehydrated. The result is a growing column of carbon black, heat, and the overwhelming odor of burnt caramel.

Easy Science Experiments

Want something less extravagant but still fun? These easy science experiments are doable with items you likely already have at home—from creating invisible ink with baking soda to making homemade ice cream in a plastic bag.

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Turning copper coins into ‘silver’ and ‘gold’

In association with Nuffield Foundation

• Four out of five

Students then witness a coin being heated in a Bunsen flame, forming an alloy of brass which makes the coin appear gold

A simple demonstration involving electroplating and the chemistry of alloys, this demonstration is suitable for any age group depending on the sophistication of the theoretical treatment used.

The demonstration takes about 10–15 minutes.

Try this in microscale

Learners can produce their own gold coins with our microscale version of this experiment .

• Eye protection (goggles)
• Beaker, 250 cm 3
• Electric heating plate
• Pair of tongs or forceps
• Glass stirring rod
• Bunsen burner
• Access to a top-pan balance
• Sodium hydroxide solution, 0.4 M, 100 ml (IRRITANT)
• Zinc powder (HIGHLY FLAMMABLE, DANGEROUS FOR THE ENVIRONMENT), 5 g
• Steel wool (note 7)
• Deionised or distilled water, 100 cm 3
• Copper coins (note 8)

Health, safety and technical notes

• Read our standard health and safety guidance .
• Wear goggles and take care to avoid skin contact.
• Sodium hydroxide, NaOH(s), (WARNING: IRRITANT) – Refer to CLEAPSS Hazcard HC091a .
• Zinc powder, Zn(s), (HIGHLY FLAMMABLE, DANGEROUS FOR THE ENVIRONMENT) – Refer to CLEAPSS Hazcard HC107 . Any solid zinc remaining in the solution (as fine powder or any clumps that have formed) should not be left to dry because it can ignite spontaneously. Dispose of it by rinsing with water, dissolving in excess dilute sulfuric acid and washing the resulting zinc sulfate solution down the sink.
• Hydrogen gas, H 2 (g), (EXTREMELY FLAMMABLE) – Refer to CLEAPSS Hazcard HC048 .
• Since hydrogen is evolved from a hot solution of zinc in sodium hydroxide an electric heating plate should be used to heat the solution and turned off before the zinc is added.
• Hot coins could cause burns. Allow to cool for at least five minutes before handling.
• If steel wool isn’t available a proprietary mild abrasive material (for example, ‘Brillo’ soap pads) can be used instead.
• Copper foil could be used instead, but coins are better since they are everyday articles, and there are bound to be requests from the audience to turn copper into ‘gold’. Strictly speaking it is illegal to ’deface coins of the realm’, so the law-abiding teacher might prefer to use foreign coins instead. It would be wise under these circumstances to ensure that the plating works, since many other alloys are used in foreign coinage.

Before the demonstration 

• Measure 100 ml of 0.4 M sodium hydroxide solution in a 250 cm 3 beaker.
• Heat the solution to boiling point on an electric heating plate.
• Turn the electric heating plate off.
• Add 5 g of zinc powder carefully. The solution will fizz as some of the zinc dissolves forming sodium zincate and giving off hydrogen.
• Clean a ‘copper’ coin with steel wool until it is shiny.

The demonstration

• Drop the cleaned coin into the hot solution containing sodium zincate and the remaining zinc powder.
• The coin must make contact with the powdered zinc at the bottom of the solution. If necessary use a glass rod to move the coin until this is so.
• Leave the coin until it is plated with a shiny coat of zinc. This will take about 2–3 minutes. Leaving the coin too long may cause lumps of zinc to stick to it.
• Remove the plated coin with tongs or forceps and rinse it under running tap water to remove traces of sodium hydroxide and sodium zincate.
• Show the ‘silver’ coin to the audience.
• Using tongs or forceps, hold the plated coin in the upper part of a roaring Bunsen flame for a few seconds until the surface turns gold. Turn the coin so that both sides are heated equally. Overheating will cause the coin to tarnish.
• Allow the coin to cool and show it to the audience.

Teaching notes

It may be sensible to carry out a trial experiment before performing the demonstration in front of an audience.

If the mixture of sodium zincate solution and zinc is cloudy, allow to cool, and then filter off the zinc to leave a clear filtrate. Place a small piece of zinc foil in the liquid as a substitute for the powder.

Younger students might want to have their own coins plated.

The theory is as follows:

The reaction between zinc and sodium hydroxide to form sodium zincate is as follows:

Zn(s) + 2NaOH(aq) + 2H 2 O(l) → Na 2 [Zn(OH) 4 ](aq) + H 2 (g)

The plating reaction involves an electrochemical cell; it will not take place unless the copper and the zinc are in contact, either directly (as here) or by means of a wire.

The electrode reactions are:

At the zinc electrode: Zn(s) → Zn 2+ (aq) + 2e – followed by complexing of the zinc ions as [Zn(OH) 4 ] 2– (aq)

At the copper electrode: [Zn(OH) 4 ] 2– (aq) + 2e – → Zn(s) + 4OH – (aq)

The coating of zinc gives the impression that the coin is now coated with silver.

You can weigh the coins before and after coating to find the mass of zinc added.

On heating the coin in the Bunsen flame, brass is formed by the zinc migrating into the surface layer of the copper. This gives a gold appearance to the coin.

Brass is an alloy of copper containing between 18% and 40% of zinc.

A similar zinc plating process is used industrially, but with cyanide ions rather than hydroxide ions as the complexing agent.

Additional information

This is a resource from the  Practical Chemistry project , developed by the Nuffield Foundation and the Royal Society of Chemistry.

Practical Chemistry activities accompany  Practical Physics  and  Practical Biology .

The experiment is also part of the Royal Society of Chemistry’s Continuing Professional Development course:  Chemistry for non-specialists .

© Nuffield Foundation and the Royal Society of Chemistry

• 11-14 years
• 14-16 years
• 16-18 years
• Demonstrations
• Properties of matter
• Redox chemistry

Specification

• 5.4C Explain how electroplating can be used to improve the appearance and/or the resistance to corrosion of metal objects
• (p) the use of electrolysis in electroplating, purification of copper and the manufacture of sodium hydroxide (and hydrogen gas and chlorine gas)

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Organic Chemistry Frontiers

Photoredox copper-catalyzed regioselective syntheses of allenols via hat-mediated propargyl radical generation.

Selectivity control of the reactions of propargylic and/or allenylic radicals remains particularly elusive. Here, a visible light-mediated Cu-catalyzed protocol for the highly selective syntheses of tri- and tetra-substituted allenols from alkynol derivatives has been developed. Synthetic potentials of the products have been demonstrated. The control experiments, Stern-Volmer quenching, and cyclic voltammetry studies support a reaction pathway involving the generation of allenyl radicals via photo-mediated N-O bond scission, intramolecular 1,5-HAT process, the resonance to propargylic radicals, and coupling. Non-common intramolecular 1,6-HAT process has also been observed.

Supplementary files

• Supplementary information PDF (29282K)

Article information

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W. Li, H. Yu and S. Ma, Org. Chem. Front. , 2024, Accepted Manuscript , DOI: 10.1039/D4QO01245C

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