clean coins experiment

Science Experiment: How to Clean Pennies

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Have you ever wondered how to clean pennies ? Cleaning copper pennies can be a lot of fun for kids! You can turn the coin from a dull brown to bright and shiny. Get out your tarnished coins & let’s get going!

I decided to turn this into science experiment with my kids to test a few different substances and see what works best to clean old coins.

I remember accidentally doing this one time with a packet of hot sauce from Taco Bell when I was in high school. That’s where this experiment idea came from! My friends & I thought it was so cool that the penny got so shiny.

Why Do Pennies Turn Brown?

Pennies are made of copper. When copper is exposed to oxygen it will corrode (turn brown) because of chemical reactions. The oxidation creates a brown coating called patina. These are copper oxide molecules and they actually protect the metal underneath. Over time, copper transitions from its shiny brown color to a darker brown shade. There are also layers of dirt and grime that build up on coins.

How to Clean Pennies:

If you are genuinely wanting to know how to clean pennies, I have learned that a mixture of vinegar and table salt will get them really clean and shiny . Soak them in the solution for a couple of minutes. Then gently scrub the pennies with a soft-bristled toothbrush. Obviously you’ll want to use an old toothbrush.  😉  Rinse the coins with warm water and use a soft towel to wipe them dry. Be careful not to create any scratches or abrasions on the surface of the coins as you clean them.

Why clean copper coins?

Coin collectors often want to clean coins. Collectible coins are typically displayed, so their owners want them looking good! You can clean your everyday coins, too if you want. But usually you only keep they for a short time. Rare coins need to be kept clean.

But for the sake of this experiment, we wanted to try some different substances to see what would work best for us. I let my kids help pick the different things to test.

We filled some cups with a small amount of different substances in our kitchen to see which one would get our dirty pennies the cleanest. I had my kids each take a guess at which thing would get the pennies the cleanest. They were way off, so it was fun to see which really did get them clean. We let the pennies soak for a time, then put them on a paper towel to dry. Next wipe or scrub the penny clean with paper towels.

Substances We Tested for Cleaning Pennies

When experimenting with how to clean pennies, we tested a variety of items, here are some ideas:

Lemon or lime juice Water Soy sauce Dish soap White vinegar Ginger ale Ketchup Salt water Hot Sauce Mustard Milk Baking soda (we did not try this, but it would be a good option to add in!)

Pour a tablespoon or so of each substance in a a bowl, jar or cup, enough to cover the penny, then allow it to sit for a time. We left ours for 30 minutes.

Our Results:

We took them out and wiped each one off on a paper towel. You can see the surface of the pennies change and become shinier. You can then rinse them with soapy water and set them on a towel to dry. You may have to wipe off some of the built-up dirt on some of them.

Vinegar and lemon juice both work really well for cleaning pennies. But, ketchup was the clear winners for our pennies, with soy sauce next, maybe with a little more time they would have gotten a little bit cleaner.

This is a fun experiment to try with younger kids! My kids of all ages were interested in the results, though. So if you want to do it with older kids, just go deeper with the science!

Use my  Scientific Method Worksheets  to extend this!

See even more  STEM projects  for kids.

Now just for the sake of preserving history, here is our original image from the first time we tried this experiment about 10 years ago. 🙂

Former school teacher turned homeschool mom of 4 kids. Loves creating awesome hands-on creative learning ideas to make learning engaging and memorable for all kids!

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Perfect! This is just the activity we need this week!

Apparently, it is the salt + acid combo that works so well…that’s why hot sauce works better than just vinegar or lemon juice…and ketchup should work just as well as hot sauce! Thank you so much for linking up with the Smart Summer Challenge!

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This would be my son science project for this year, than k you!!!!

Yeah! You are most welcome!

on the last penny to the lower right “clean-pennies.jpg” what did you use?

The one on the bottom row to the right (I think that’s the one you mean)- That one was soy sauce.

Thank u soooooo much! i needed to find a science project for schoool and it is due tommorow! luckily i found this!

What a fun experiment!! I did it with my husband for a date night. He predicted the vinegar and I predicted the salt solution. We used dish soap, soy sauce, vinegar, lime juice, ketchup and salt solution. But our results were different. All the pennies were very clean afterward. No brown ones left, except a stubborn stain here and there. To my surprise, the shiniest one was the one soaked in dish soap. No brown left at all!. I thought the dish soap would have performed the worst! Thanks for sharing thisa

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Cleaning Coins Experiment [Procedure And Explanation]

Today is the day you take out your old coins and declare this day, coin cleaning day.

Get your copper coins out of the containers where they’ve been hiding for many years and get them cleaned.

You don’t need any fancy gadgets or science kits to clean these coins, all you need are a few household ingredients and you will have shiny new coins in less than an hour.

Before you start, it’s important to take note that for this cleaning coins experiment to work, you need coins made of copper; otherwise, this will not work.

Note: Some of the links on this page are affiliate links. 

chemistry, kitchen science experiments , coin experiments

Questions To Ask Before The Experiment:

• What can clean pennies the best?
• Why do you think coins lose their shine?
• We are going to put the coins into different liquids, which of these liquids do you think will clean them?

You will need:

• 1/4 cup of catsup
• 1/4 cup of coke
• 1/4 cup of apple juice
• 1/4 cup of water
• 1/4 cup of vinegar
• 1/4 cup of vinegar + salt
• kitchen paper
• stick or teaspoon for mixing
• 6 old copper coins
• strips of paper for labeling

Step by Step Procedure:

There are two different stages to this Science activity . You don’t have to do the 2nd one, but it’s also a good scientific experiment and you’ll even find out why the Statue of Liberty is the color that it is.

• First, prepare all your cups and line them up. Since we have 6 different liquids here, it’s best to properly label each cup. Write the name of each liquid on a strip of paper and put one strip beside the cup to mark it.
• Next, pour one liquid into each cup. So 1st cup will have catsup, 2nd will have coke, and so on.
• Afterwards, put one old coin in each cup.
• Leave the coins in the liquid for 10 minutes.  (You may need to push the one in the catsup to get it fully submerged). If you’re doing this with kids, this is a good time to ask them questions about the experiment. Which one do they think will clean the coin the most? What will happen when the liquid cleans the coin?
• After 10 minutes, use your tweezers to take the coins out of each cup. (we used our hands — very messy business especially with the catsup but the kids thought that was fun!) .
• Finally, wipe the coins dry with a tea towel or kitchen paper. Now closely look at each coin. Which one is the cleanest?  the shiniest?

Video: Stage 1 Coin Cleaning Experiment

Here is a video of when we did the first stage of this experiment which we put up on our GallyKids Youtube Channel . Check it out. We’ll try and put up the next stage soon. And also, don’t forget to Subscribe to our channel for more fun kids activities

Most of the liquids (except the water) should have somewhat cleaned the coin. The vinegar + salt mixture and the ketchup will have come out as the clear winners.

So for the 2nd stage of this experiment, you will work on these two materials alone.

• First, put the coins back into the same mixture as the one you used in the first experiment. Remember, you will be working with only the vinegar salt mixture and the catsup. This means you will only have two cups to work with.
• Leave the coins for 10 minutes.
• After 10 minutes, take the coins out; but this time, don’t wipe the coins clean. Just put the coins on the tea towel and leave it to air dry.
• Finally, after about 30 minutes to 1 hour, look at the coins again. What has happened to the coins?

Quick & Easy Explanation

So what just happened here? Did you get to the same conclusion that the ketchup and the vinegar + salt mixture cleaned the coins the most?

Why do you think this happened?

Remember that at the very start, I said you should use only copper coins? There’s a reason for that.

You see, copper coins are usually shiny and well, copper-colored. In time, however, they get darker, brownish and dull.

The reason for this is that copper has quite the relationship with Oxygen that is they react to each other.

So when the coin stays in your pocket or is passed from person to person or stays in that container where you keep all your pennies, the copper in the coin reacts with the oxygen in the air and turns into what is called copper oxide.

Copper oxide is blackish. It’s that dull dark color that coats old coins.

Also, Copper oxide easily dissolves in acid.

And what is vinegar? It’s acid! So, the acetic acid in vinegar dissolves the copper oxide and cleans it. So if you look at the coin in the vinegar solution, it made the old coin a little bit brighter and less brown.

But here’s the question that I’m sure is brewing in your mind….

But the vinegar by itself didn’t clean the coin as well as the vinegar + salt solution! Why is that?

It turns out that when you mix vinegar and salt, a chemical reaction takes place and  form what is called hydrochloric acid.

And hydrochloric acid is so much more acidic than vinegar alone.

Isn’t that amazing? You simply add salt to vinegar and you end up making an even more acidic concoction? That’s Chemistry in action for you!

And because this mixture is way up high in the acidic scale, it cleaned the coin so much better and quicker than just vinegar.

And now the 3rd question arises.

But what about the ketchup? Why did the catsup clean the coin as well as the vinegar + salt solution?

Well, it’s time to look at what is in our catsup! And see what’s the science behind this phenomena.

So in our case, we looked at the ingredients. We know that it’s mostly tomatoes – a quite acidic vegetable. But we think that that alone could not clean coins this quickly.

So we proceeded to read the other ingredients  and guess what we found? Salt!

And it even had added acetic acid! You can only guess how highly acidic this ketchup must be!

So there you go, that’s how it cleaned the coins too.

Did you do the 2nd stage of this cleaning coins experiment? What happened to the coins when air dried?

They turned bluish-green, right?

Here’s what happened to your coin.

When the vinegar cleaned the coin, it stripped away the coating and exposed the copper.

Now when you dipped it into the salt + vinegar solution and then air-dried it, it also took with it some chlorine which is often found in salt.

And here’s where the science matters.

Remember that copper turns dark brown when reacting with oxygen? Well, here’s something even more fascinating. When you add chlorine in that mix, the color turns bluish-green instead!

This bluish-green color is called Malachite.

It’s exactly the same reaction that’s happening to the dearly beloved Statue of Liberty!

Yes, that’s right. The statue is made of copper and it has turned bluish-green because of this copper-oxygen-chlorine reaction.

Isn’t that a cool and fun fact?

2 thoughts on “Cleaning Coins Experiment [Procedure And Explanation]”

This website is helpful to me but,add more steps and I think it can be more helpful.

Thanks a lot Meriley. We’ll keep that in mind. 🙂

Comments are closed.

Cleaning Pennies Science Experiment for Kids

Have you ever wondered why some pennies are shiny and some are dull? It’s not just dependent on how old the pennies are. Chemical reactions are responsible for the change in a penny’s appearance over time.

Kids will love trying their hand at the classic cleaning pennies science experiment to see if they can use a chemical reaction to make pennies shine brightly once again.

Cleaning Pennies Science Experiment

If you have dirty, dull, or green pennies lying around, try the cleaning pennies science experiment to turn them bright again! You need just a few things for this experiment:

• Dull pennies
• Small container (we used a beaker)
• Paper towels

Create a solution of vinegar and salt using one teaspoon of salt and 1/4 of a cup of vinegar. Mix until the salt is dissolved (it helps if the vinegar is a little warm). Add the pennies.

Wait about 5 minutes, then remove the pennies from the solution. Dry the pennies with a paper towel.

The pennies will be cleaner and brighter than before.

Repeat the experiment with the same pennies in a new solution of vinegar and salt and see if you can make them even brighter!

Will using lemon juice and salt have better results than vinegar? Try other materials containing small amounts of acid to see which produces the best results. Ketchup and oranges have a high acid content as do vinegar and lemons.

Cleaning Pennies Science Experiment Explained

Pennies turn dull and green due to oxidation. Over time, pennies form a layer of copper oxide on the surface of the penny, which actually protects it from further corruption. After quite some time, or after exposure to an acid, pennies will form copper sulfate, carbonate, and chloride salts, which gives pennies a green color. Washing the pennies in a vinegar and salt solution removes the patina from the pennies, exposing the brighter copper underneath once more.

More fun science for kids:

Copper Caper

What do i need.

• 20 dull, dirty pennies
• 1/4 cup white vinegar
• 1 teaspoon salt
• A clear, shallow bowl (not metal)
• 2 clean steel nails
• A clean steel screw or bolt
• Paper towels

What do I do?

Put the salt and vinegar in the bowl. Stir until the salt dissolves.

Dip one penny halfway into the liquid. Hold it there for about 10 seconds, then pull it out. What do you see?

Dump all the pennies into the liquid. You can watch them change for the first few seconds. After that you won't see anything happen.

After 5 minutes, take half of the pennies out of the liquid. Put them on a paper towel to dry.

Take the rest of the pennies out of the liquid. Rinse them really well under running water, and put them on a paper towel to dry. Write "rinsed" on the second paper towel.

Put a nail and a screw into the liquid. Lean another nail against the side of the bowl so that only part of it is in the liquid.

After 10 minutes, take a look at the nails. Are they a different color than they were before? Is the leaning nail 2 different colors? If not, leave the nails in the bowl and check on them again in an hour or so.

What's happening to the screw? You may see lots and lots of fizzing bubbles coming from the threads. Is the screw changing color? Leave it in the liquid for a while and see what happens.

After about an hour, look at the pennies on the paper towels. What's happened to the ones you rinsed? What's happened to the others? What color is the paper towel under the un-rinsed pennies?

What's Going On?

Why did the pennies look dirty before i put them in the vinegar.

Everything around you is made up of tiny particles called atoms. Some things are made up of just one kind of atom. The copper of a penny, for example, is made up of copper atoms. But sometimes atoms of different kinds join to make molecules. Copper atoms can combine with oxygen atoms from the air to make a molecule called copper oxide. The pennies looked dull and dirty because they were covered with copper oxide.

Why did the vinegar and salt clean the pennies?

Copper oxide dissolves in a mixture of weak acid and table salt-and vinegar is an acid. You could also clean your pennies with salt and lemon juice or orange juice, because those juices are acids, too.

Why did the unrinsed pennies turn blue-green?

When the vinegar and salt dissolve the copper-oxide layer, they make it easier for the copper atoms to join oxygen from the air and chlorine from the salt to make a blue-green compound called malachite.

How did the nail and the screw get coated with copper?

To understand how the nail and screw got coated with copper, you need to understand a little bit more about atoms. Atoms are made up of even smaller particles called protons, neutrons, and electrons. Electrons and protons are both electrically charged particles. Electrons are negatively charged and protons are positively charged. Negative charges attract positive charges, so electrons attract protons.

When you put your dirty pennies in the vinegar and salt, the copper oxide and some of the copper dissolve in the water. That means some copper atoms leave the penny and start floating around in the liquid. But when these copper atoms leave the penny, they leave some of their electrons behind. Rather than having whole copper atoms in the liquid, you've got copper ions, copper atoms that are missing two electrons. These ions are positively charged.

Now add two steel nails and a screw to the mixture. Steel is a metal made by combining iron, other metals, and carbon. As you found out when you cleaned your pennies, your mixture of salt and vinegar is really good at dissolving metals and metal oxides. When you put the steel nail in the mixture, some of the iron dissolves. Like the copper atoms, each of the iron atoms that dissolves leaves two electrons behind. So you've got positively charged iron ions floating in your vinegar with the positively charged copper ions.

Originally, the steel nail was neutrally charged-but when the iron ions left their electrons behind, the nail then became neg-atively charged. And remember what we said way back at the beginning of this section: negative charges attract positive charges. The negative charges on the nail attract positive charges in the liquid. Both the iron ions and the copper ions are positively charged. The copper ions are more strongly attracted to the negative charge than the iron ions, so they stick to the negatively charged nail, forming a coating of copper on the steel.

Why did bubbles come off the steel screw?

Each water molecule is made up of two hydrogen atoms and an oxygen atom. In an acid (like vinegar or lemon juice), lots of hydrogen ions (hydrogen atoms that are missing an electron) are floating around. In the chemical reactions at the surface of the screw, some of these hydrogen ions join and form hydrogen gas. The bubbles that you see coming off the screw are made of hydrogen gas.

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Clean or Green Pennies

Use a simple chemical reaction to clean pennies or turn them green!

Grades: 3rd grade and up

Materials: 4 or more pennies (some from before 1982, if possible), vinegar, salt, 2 small non-metal bowls, paper towel

Time: 10 minutes (active time), 60 minutes (wait time)

• Place a piece of paper towel in the bottom of each small bowl. Remember, do not use metal bowls.
• Place two pennies in each bowl. Note: Pennies made before 1982 have a higher copper content than pennies made after 1982. The chemical reactions in this experiment will be more visible with the older pennies since they have more copper.
•  In Bowl 1, pour in a little bit of vinegar to soak the paper towel. Let this bowl sit for one hour.
• In Bowl 2, pour in some vinegar and salt. Swirl or stir to dissolve the salt. Within about 30 seconds, the pennies in this bowl will start to shine. The vinegar and salt mixture dissolves the outer layer of dirt. Flip the pennies over and wait another 30 seconds. Then remove them, rinse them with water, and dry. Now you have two clean, shiny pennies!
• After an hour, check on Bowl 1. You should start to see a green layer forming on the pennies.

What is happening?

In Bowl 1, the vinegar helps speed up a chemical reaction between the copper in the penny and the oxygen in the air. This reaction is called oxidation. When copper oxidizes, it turns a blue-green color, forming a compound called malachite.

In Bowl 2, the vinegar and salt create a chemical reaction. This reaction dissolves the copper oxide (the dirty looking spots) and some of the copper on the outside of the penny. The result is a shiny looking penny!

What Cleans an Old Penny?

The average U.S. coin is in circulation for 30 years, so it’s no surprise that coins get dirty! Pennies, with their copper exterior, often look especially tarnished. Try this experiment to see if soap or vinegar does a better job at making pennies shine again.

What You'll Need

Guess which liquid will make a penny shine.

Set one penny aside. Put each of the other two pennies into its own paper cup.

In one cup, pour enough vinegar to cover the penny.

In the other cup, pour enough liquid soap to cover the penny.

Wait at least ten minutes.

Remove the pennies, rinse them in water and rub them with a paper towel.

Compare all three pennies.

How It Works

The vinegar made its penny shiny. Pennies become dull over time as copper on the surface reacts with oxygen from the air. The two elements combine to form dark chemicals called copper oxides. The acetic acid in vinegar dissolves these chemicals and leaves the copper surface of the penny looking shiny. Soap can clean lots of things, but it can’t dissolve copper oxides.

Extend the Fun

Younger kids: Do the experiment again with more pennies. With your child, collect 10 pennies and count them one at a time. Before the pennies go in the vinegar, talk about what they look like. Think about color, shape and size. Repeat the experiment and then talk again after the pennies are shiny and rinsed. What is different about the pennies? What is the same? Finish up by counting the pennies again and adding them to your child’s piggy bank.

Older kids: In this experiment, you left the penny in the vinegar for 10 minutes. What do you think would happen if you left it in for 30 seconds? What if you left it in for an hour? What would happen if you put only part of the penny in the vinegar? Make a guess and test these ideas with other pennies. If you run out of vinegar, you can also use other acidic liquids, such as lemon juice or pickle juice. See how they compare!

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How To Clean Pennies – Science Experiment For Kids

What do you use to clean coins?

For this experiment, we used several solutions that could clean our coins. We used baking soda and water, vinegar, soap and water, ketchup, and orange juice. We let our coins sit for about 2 hours as we ran errands. I also setup a mini baking soda vinegar surprise experiment where I hid in a few drops of food coloring.

After the coins sat long enough in the solutions, we simply cleaned with water and laid them out to analyze. Both boys seem to agree that baking soda and water cleaned and shined their coins the best.

We did a little coin counting afterward because you know, we have to add in a little math 😏.

Have you tried this experiment yet? How did it go?

Ice cube tray (2)

5 cups to hold each solution: Orange Juice, Vinegar, Ketchup, Baking Soda & Water, Vinegar, Soap & Water

5 coins of each (5 pennies, 5 nickels, 5 dimes, 5 quarters) and few extra for the “control”.

Directions:

• Gather all of your coins and lay neatly. Analyze how each looks. Have a few extra for the control to compare to later.
• Put all the pennies in the first row, nickels in the second, dimes in the third, and quarters in the fourth row.
• For each column starting with the first, add in baking soda and water to the penny, nickel, dime and quarter. Do the same for each set of 4 coins in a column- Second column add in vinegar; Third column add in soap and water; Fourth column add in ketchup; and the fifth column add in orange juice.
• Let the solution sit for at least 30 minutes.
• Rinse with a clean bowl of water and set on a paper towel.
• Compare the coins to the control and conclude which solution cleans the coins best.

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Penny Cleaning Experiment - Teach Kids about Phosphorus

Posted by Admin / in Chemistry Experiments

Pennies have a copper coating that when new looks very shiny. As the copper gets older, it reacts with the oxygen in the air and begins to form a copper-oxygen compound. This compound makes the penny look dull brown. This experiment helps to teach kids how to use the phosphor content in Coke or Pepsi to clean pennies.

Materials Needed

• dirty pennies
• disposable cup
• dark cola like Coke or Pepsi
• permanent marker

EXPERIMENT STEPS

Step 1: Pour a couple of inches of Coke or Pepsi (any dark cola will work) in the bottom of a disposable cup.

Step 2: Using the permanent marker, mark an X on one side of several of the pennies. Record which pennies that were marked by writing down the year of each penny.

Step 3: Drop a few pennies in the bottom of the cup. Most pennies that were minted before about 1982 have much more copper content than newer pennies. It is fun to try some newer pennies and a few older pennies to experiment with the results.

Step 4: Let the pennies sit in the cola overnight.

Step 5: Pour the cola down the drain, leaving the pennies behind. Never drink the cola used in this experiment. The residual copper left in the cola can make you sick. Also, throw away the cup after using it for the experiment.

Step 6: Compare the pennies used in the experiment to other uncleaned pennies

Science Learned

Dark colas like Coke and Pepsi actually contain phosphor in the form of phosphoric acid. This acid breaks down the copper-oxygen compound chemical bonds allowing a fresh unoxidized layer of copper to be exposed. The copper which is removed from the surface of the pennies ends up in the cola in the form of copper ions. Another great experiment to make use of copper ions removed from pennies can be found in the Copper Plating Experiment .

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Cleaning Pennies

Does the amount of salt affect the shine of a rusted penny when mixed with white vinegar?

2014 Elementary Project Contest Winning Submission Submitted by: Mariam A.

Project Details

Grade Level

• White Vinegar
• Measuring Cup
• 3 Teaspoons
• 3 Rusted Pennies

Label one bowl as 0 tsp, one as 2 tsp, and the last one as 4 tsp. Fill each bowl with 1/8 cup of white vinegar. Pour the salt in the bowl. Put 0 tsp in the first bowl,2 tsp in the second one and 4 tsp in the last one. Stir each bowl. Lastly, put one penny on each spoon and drop one penny in each of the bowls at the same time (you might need to get help so you can drop them at the same time). Let the pennies soak overnight and check the next day. Remove the pennies from the bowl and make observations.

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May 25, 2017

Shine Bright Like a...Penny!

A shiny new chemistry activity

By Science Buddies & Megan Arnett

A chemistry activity that makes good cents

George Retseck

Key concepts Chemistry Chemical reactions Acidity Oxidation

Introduction “See a penny, pick it up—all day long you’ll have good luck!” Maybe you’ve heard this phrase before, and maybe you’ve even stopped to pick up a lucky penny off the sidewalk. But sometimes those pennies you see on the ground look anything but lucky. They appear brown or black, and sometimes they’re so dirty looking you can’t even tell whether they’re pennies!

In this activity we’re going to explore why pennies don’t stay bright and shiny, and test different methods to bring their shine back!

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Background All pennies start out the same color—bright copper. But somewhere along the way, those pennies lose their luster. What happens?

The answer is pretty simple: Although copper is a shiny metal, it is also reactive. The negatively charged oxygen atoms in our air are attracted to the positively charged copper atoms in the penny. When oxygen binds with copper, they form a new molecule known as copper oxide. Copper oxide is brownish or sometimes black in color (depending on other things in the penny's environment). This is why most pennies you see look dirty or tarnished—it’s not actually dirt but copper oxide that makes them look so dull.

Luckily, there are a number of ways to clean pennies and make them look bright and shiny again—using chemistry! We’re going to test a few different methods for cleaning pennies and determine which gets our pennies the cleanest.

Set of measuring spoons

10 very tarnished pennies (The more tarnished the better—and the activity works best with pennies that are about equally tarnished.)

Two tablespoons of baking soda

Four teaspoons of salt

Two tablespoons of white vinegar

Two tablespoons of freshly squeezed lemon juice

Two tablespoons of ketchup

Two tablespoons of Tabasco sauce (or other hot sauce)

11 plastic cups (Small Tupperware containers or bowls will work as well.)

Pen or pencil

Dishwashing gloves

Permanent marker

A timer or clock

Paper towels

Access to a sink

Camera (optional)  

Preparation

Make a paste from your baking soda and water: Pour one quarter cup of baking soda into one of your plastic cups. Slowly add water, one tablespoon at time, until you’ve created a paste.

Use your permanent marker to label your plastic cups as described below. If using bowls or Tupperware, write your label on clear plastic tape and gently attach it.

Cup labels—on each of the remaining cups place a label as follows: Ketchup 1 Ketchup 5 Tabasco 1 Tabasco 5 Vinegar 1 Vinegar 5 Lemon 1 Lemon 5 Control 1 Control 5

Put one tablespoon of ketchup into each “Ketchup” cup. Put one tablespoon of Tabasco into each “Tabasco” cup. Put one tablespoon of vinegar and one teaspoon of salt into each “Vinegar” cup. Put one tablespoon of lemon juice and one teaspoon of salt into each “Lemon” cup. Leave the “Control” cups empty.

Use your paper and pencil to create a table with three columns and six rows that lists your five test substances (ketchup, Tabasco sauce, vinegar, lemon juice and control) in a column on the left. Label this column “Cleaning Method.” The next column, label “1 Minute.” And label the third column “5 Minutes.” Make each cell (square) of the table large enough to place your penny in it after your testing is complete. Do you have a hypothesis about which substance will best clean a tarnished penny? Why?

Place a penny on each square of your table, heads side up. If you have a camera, take a picture of the pennies. If you don’t have a camera, look closely at the color of each penny. This will allow you to make a better judgment of how well each method cleaned, by looking at the pennies before and after their treatment. What do you notice about each penny? Can you clearly see the date on the penny or is it too dirty? Can you clearly see Abraham Lincoln’s profile?

Start with the cups labeled “1.” Line these cups up in a row. Take the penny from the “Ketchup, 1 Minute” square of your table, and place it in the “Ketchup 1” cup. Gently swirl the cup so the penny is completely covered with ketchup.

Start a one-minute timer.

Put on your dishwashing gloves.

When one minute has passed, rinse the cup with water until its inside and the penny is clean. (Be careful not to lose your penny.) Keep the penny in the cup.

Repeat this procedure with each of the other pennies in the “1 Minute” column, in turn placing each into their corresponding cup. In each case, make sure the penny is completely covered by the contents of the cup.

For the “Control, 1 Minute” penny do not add anything to the cup. This is your control. Complete the full procedure.

Once all of the “1 Minute” pennies have been rinsed, use your fingers to gently scrub the pennies one at a time with your baking soda paste. Keep your gloves on for this part, being careful to keep each penny with its labeled cup. Scrub each penny for 10 seconds, then rinse it again with water and place it back into its cup.

Set these cups aside for now.

Repeat these steps with the pennies in your “5 Minutes” column. Start by placing the “Ketchup, 5 Minutes” penny into the cup labeled “Ketchup 5.” Again, make sure the penny is completely covered by ketchup.

Start a timer for five minutes.

Continue to place each penny in the “5 Minutes” column in its corresponding cup.

Once all the pennies are in their correct cups, use the remaining time to observe the pennies and the contents of the cups. Do you notice any changes in the appearance of the pennies? What is changing? Do you notice any changes in the contents of the cups? Is anything bubbling or changing color?

Once five minutes have passed, rinse the cups with water until their insides and the pennies are clean. (Be careful not to lose your pennies). Keep the pennies in the cups.

Once all of the pennies have been rinsed, use your fingers to gently scrub the pennies one at a time with your baking soda paste. (Again, keep your gloves on for this part.) Scrub each penny for 10 seconds, then rinse it again with water and place it back into its cup.

Go back to the table you drew. Use your paper towels to gently dry off each penny then place it in the corresponding square of your table.

Compare the “1 Minute” and “5 Minutes” pennies in each row. How does time affect the cleanliness of the pennies? Was one or five minutes more effective in cleaning the pennies overall? Can you think of why time would be important? Were there any cleaning methods where the time didn't matter, so the "1 Minute" and "5 Minutes" pennies are equally clean? Why do you think this might be?

Compare all of the cleaned pennies with the control ones. Which penny looks the cleanest compared with the control? Which is still the most tarnished?

If you took a picture at the beginning, go back and compare each penny's cleanliness before and after being cleaned. Which penny is the cleanest compared with its before picture? Which is the least clean?

Extra: Test even longer periods of time with each of the cleaning methods. What is the optimal time to leave the pennies in the cleaning solution?

Extra: Test whether these cleaning solutions work on other types of coins. What do your results tell you about the special properties of copper pennies?

Extra: Can you think of other safe household acids you could test? What about soda? Orange juice?

Observations and results In this activity you tested four different cleaning methods to determine which was the most effective at cleaning pennies. You should have observed that each cleaning method made the pennies cleaner but some methods may have been more successful than others. Which method works best is determined by the amount of acid and the presence of salt. Different brands of ketchup and hot sauce will have different amounts of salt and acid in their ingredients, so your results might be different than someone else doing this activity at their house. In each case, however, the cleaning method that should have worked best for you is the one that has the highest concentration of acid.

As they are exposed to the environment, pennies become coated with a layer of copper oxide, making them look tarnished (with a dull, brown, dirty appearance). Copper oxide dissolves in a mixture of weak acid and table salt. Vinegar and lemon juice are both acids. Check the ingredient list for your ketchup and Tabasco sauce—some of the labels might list vinegar or citric acid whereas others might say tomato puree. Tomatoes contain some naturally occurring citric acid, another acid that is generally slightly weaker than vinegar or the amount of citric acid in lemon juice. Therefore, each cleaning method you tested contained acid and salt but the ketchup and Tabasco sauce may have had a slightly weaker acid. In this case, you might have noticed the ketchup and Tabasco pennies were not quite as well cleaned as the pennies that were in the vinegar and lemon juice.

You also might have also noticed the longer the pennies stayed in the cleaning solution, the cleaner-looking they became! The chemical reaction that dissolves the copper oxide on your pennies is an ongoing process. Leaving your pennies in the cleaning solution longer gives the reaction more time to continue, and gives you shinier pennies!

More to explore From Dull to Dazzling: Using Pennies to Test How pH Affects Copper Corrosion , from Science Buddies Rusting Out: How Acids Affect the Rate of Corrosion , from Science Buddies Cabbage Chemistry—Finding Acids and Bases , from Scientific American Science Activities for All Ages! , from Science Buddies

This activity brought to you in partnership with Science Buddies

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Clean pennies with vinegar, you will need.

* A few old (not shiny) pennies * 1/4 cup white vinegar * 1 teaspoon salt * Non-metal bowl * Paper towels

Pour the vinegar into the bowl and add the salt – stir it up. Put about 5 pennies into the bowl and count to 10 slowly. Take out the pennies and rinse them out in some water. Admire their shininess!

How does it work?

There is some pretty fancy chemistry going on in that little bowl of yours. It turns out that vinegar is an acid, and the acid in the vinegar reacts with the salt to remove what chemists call copper oxide which was making your pennies dull. You’re not done yet, though, lets try another experiment:

Add more pennies to the bowl for 10 seconds, but this time , don’t rinse them off. Place them on a paper towel to dry off. In time the pennies will turn greenish-blue as a chemical called malachite forms on your pennies. But wait, you’re still not done yet.

Place one or two nuts and bolts in the vinegar and watch – they may become COPPER in color! The vinegar removed some of the copper from the pennies, if there is enough copper in the vinegar, the copper will become attracted by to the metal in the nuts and bolts and they will take on a new copper color – cool.

MAKE IT AN EXPERIMENT

The project above is a DEMONSTRATION. To make it a true experiment, you can try to answer these questions:

1. Will other acids (like lemon juice or orange juice) work as well?

2. Does this cleaning chemistry work on other coins?

3. Do other amounts of salt make a difference in the chemistry of the experiment?

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Dirty Pennies Kitchen Science Experiment

In this fun and easy kitchen science experiment for kids, we’re going to use a chemical reaction to clean pennies. 

• Dirty pennies
• Measuring spoons
• Paper towels

Instructions:

• Fill the glass about halfway full with vinegar.
• Stir in about one teaspoon of salt and mix until it dissolves.
• Drop eight to ten of the dirty pennies into the solution.
• After several minutes, remove half of the pennies and place them on a paper towel to dry.
• Now remove the remaining pennies. Do not these pennies and place them on a separate paper towel to dry.
• Observe the difference between the two groups of pennies.

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How it Works:

The vinegar is an acid and reacts with the salt to remove the copper oxide from the pennies. This will make the pennies look shiny as the copper oxide is what gives the pennies a dirty and tarnished look. The copper oxide comes from the pennies reacting with the oxygen in the air. The vinegar on the second batch of remaining pennies will help them form malachite which will turn the pennies bluish-green. 

Make This A Science Project:

Before disposing of your vinegar, add other metal object like washers, nails, or bolts and observe what happens. Try other types of acid like lemon juice. Try adding more salt. 

EXPLORE TONS OF FUN AND EASY SCIENCE EXPERIMENTS!

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Science project, cleaning coins.

Grade Level: 6th to 8th; Type: Chemistry

This project explores the effectiveness of various cleaning solutions in cleaning tarnished and oxidized coins.

Research Questions:

• Do the coins become clean or do they remain tarnished or oxidized?
• Which cleaning solution works best?
• How much effort does it take?
• Do the copper pennies get cleaner than the other coins?
• Do the oxidized coins get cleaner than the tarnished coins?
• Six pennies (tarnished or oxidized)
• Six nickels (tarnished or oxidized)
• Six dimes (tarnished or oxidized)
• Six quarters (tarnished or oxidized)
• One cup dish liquid
• One cup lemon juice
• One cup orange juice
• One cup water
• One cup cola
• One cup baking soda paste (Mix baking soda with water for a paste consistency.)
• Six plastic spoons
• Six toothbrushes
• Newspaper or art cloth (to cover the table)
• Latex gloves (optional)

Experimental Procedure:

• Fill four cups each one quarter full with each of the six cleaning solutions suggested (4 with lemon juice, 4 with orange juice, 4 with cola, 4 with water, 4 with baking soda paste and 4 with dish liquid). Label the cups.
• Carefully record each coin’s condition prior to placing it into its cup.
• Place one of each type of coin into each solution.
• Let all coins soak overnight.
• Using the plastic spoons and latex gloves, scoop each coin out of its cup and place it on the covered table. Take care to label and keep track of which coin came from which solution.
• Examine the coins and record what you see before you start using the toothbrushes.
• Use the toothbrushes to clean the coins, rinse with water, re-examine the coins, and record your observations.
• Address the research questions.

Terms/Concepts: oxidation, tarnish, chemical

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Green Pennies Experiment

Why is the Statue of Liberty green? It’s a beautiful patina, but how does it happen? Explore the science in your own kitchen or classroom by making green pennies ! Learning about the patina of pennies is a classic science experiment for kids!

PENNY EXPERIMENTS

Science experiments with things found in your purse or pocket? Get ready to add this simple penny experiment to your science activities this season. If you want to learn how to turn pennies green and what cleans them, let’s dig in! While you’re at it, make sure to check out our other penny experiments.

TRY THESE PENNY EXPERIMENTS

• Penny Spinner STEAM Project
• Drops on a Penny Lab
• Skeleton Bridge
• Sink the Boat Challenge
• Strong Paper Bridge Challenge

Our science activities and experiments are designed with you, the parent or teacher, in mind! Easy to set up, quick to do, most activities will take only 15 to 30 minutes to complete and are heaps of fun! Plus, our supplies lists usually contain only free or cheap materials you can source from home!

WHY DO PENNIES TURN GREEN?

Get yourself a dozen dull pennies and try out a double science activity with polishing pennies and making green pennies. Either one is a fun science activity in itself, but together they make a great science project and help kids to understand further why green pennies and the Statue of Liberty look the way they do!

DULL PENNIES ARE THE BEST TO START WITH…

We know that copper is shiny and bright, so why do these pennies {that are copper} look dull? Well, the atoms in the copper when mixed with oxygen atoms in the air form copper oxide which is the dull surface appearance of the penny. Can we polish it? YES, keep reading to find out!

Adding the green pennies to a mixture of salt and acid {vinegar} dissolves the copper oxide and restores the copper atoms to their shiny state.

What is the scientific method?

The scientific method is a process or method of research. A problem is identified, information about the problem is gathered, a hypothesis or question is formulated from the information, and the hypothesis is put to the test with an experiment to prove or disprove its validity. Sounds heavy…

What in the world does that mean?!? The scientific method should be used as a guide to help lead the process. It’s not set in stone.

You don’t need to try and solve the world’s biggest science questions! The scientific method is all about studying and learning things right around you.

As kids develop practices that involve creating, gathering data evaluating, analyzing, and communicating, they can apply these critical thinking skills to any situation. To learn more about the scientific method and how to use it, click here.

Even though the scientific method feels like it is just for big kids…

This method can be used with kids of all ages! Have a casual conversation with younger kiddos, or do a more formal notebook entry with older kiddos! You can even turn this into a science fair project!

• Easy Science Fair Projects
• Science Project Tips From A Teacher
• Science Fair Board Ideas
• Variables In Science

Click here to get your FREE printable mini Science Pack !

PENNY SCIENCE EXPERIMENT

• So what makes green pennies green?
• What is copper?
• What does all this have to do with the Statue of Liberty? 
• white vinegar
• bowl with a good size bottom base
• paper towels

PENNY EXPERIMENT SET UP:

STEP 1: Prep the green pennies science experiment by filling 2 small bowls with about 1/4 cup of vinegar and a teaspoon of salt each. Mix thoroughly.

STEP 2: Before dropping about 5 pennies into the bowl. Take one and dip it halfway into the bowl. Count to 10 slowly and pull it out. What happened?

Add a few more pennies and let them sit for a few minutes. What can you see happening?

Make sure to add 6 pennies to the other bowl too.

STEP 3: Now, take the pennies from one bowl, rinse them and let them dry on a paper towel. Take the other pennies from the other bowl and place them directly on another paper towel (do not rinse). Let’s wait and see what happens.

Alternatively, try out other acids like lemon juice and other citrus juices and see which ones work best!

Can you see the differences between the two groups of pennies, the rinsed and unrinsed pennies? Do you now have some green pennies? I bet you do! Your dull pennies should either be green or polished!

GREEN PENNIES AND THE STATUE OF LIBERTY

Your green pennies have what is called a patina. A patina is a thin layer that has formed on the surface of your copper penny from “weathering” and oxidization from the chemical process we just put the penny through.

Why is the Statue of Liberty Green?

The Statue of Liberty is covered in a thin layer of copper. Because she sits out in the elements and is surrounded by salt water, she has a patina similar to our green pennies. It would be a huge job to polish her!

MORE FUN SCIENCE EXPERIMENTS

Kids’ science experiments are numerous! Easy to set up, budget-friendly, and filled with opportunity!

• Rubber Egg in Vinegar Experiment
• Easy Sandbox Volcano
• Magic Pepper Demonstration
• Salt Water Density
• Walking Water
• Oobleck Recipe

Printable Science Projects For Kids

If you’re looking to grab all of our printable science projects in one convenient place plus exclusive worksheets and bonuses like a STEAM Project pack, our Science Project Pack is what you need! Over 300+ Pages!

• 90+ classic science activities  with journal pages, supply lists, set up and process, and science information.  NEW! Activity-specific observation pages!
• Best science practices posters  and our original science method process folders for extra alternatives!
• Be a Collector activities pack  introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
• Know the Words Science vocabulary pack  includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
• My science journal writing prompts  explore what it means to be a scientist!!
• Bonus STEAM Project Pack:  Art meets science with doable projects!
• Bonus Quick Grab Packs for Biology, Earth Science, Chemistry, and Physics

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• cleaning-coins

Cleaning Coins

This experiment is disgustingly fun but might just make you think twice the next time you fancy having a taste of a fizzy drink. Let’s get started!

What Do I Need?

• Some copper coins
• Patience (not too much needed!)

How Do I Do It?

STEP1 - When you’re out and about collect up some copper coins. The older and dirtier the better.

STEP2   - Pour out a glass of your cola.

STEP3   - Cover one side of each coin with Blu-Tac but leave the other side open.

STEP4   - Pop your coins into your glass of coke.

STEP5 - Sit back and wait but you should be able to see a difference in the colour of your coins within about an hour.

What’s Going On?

If you put some copper coins in a glass of water for a couple of days would that make them clean?

Nope! So we know that it’s something within the cola that’s causing the change but what? Well, cola is acidic. It’s actually the acid within the cola that’s reacting with the rust on the surface of our coins and causing them to return to their original shiny selves.

Our cola contains phosphoric acid which is why cola is acidic. The acid reacts with the oxide rusty coating that has covered our coins and returns them back to almost as good as new.

More Fun Please! - Experiment Like A Real Scientist!

• Does using diet or regular cola make any difference?
• What about testing out different brands of cola?
• Does it have to be cola that we use?
• What about giving vinegar or lemon juice a try?

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