potassium iodide and hydrogen peroxide experiment

• Science Notes Posts
• Contact Science Notes
• Todd Helmenstine Biography
• Anne Helmenstine Biography
• Free Printable Periodic Tables (PDF and PNG)
• Periodic Table Wallpapers
• Interactive Periodic Table
• Periodic Table Posters
• Science Experiments for Kids
• How to Grow Crystals
• Chemistry Projects
• Fire and Flames Projects
• Holiday Science
• Chemistry Problems With Answers
• Physics Problems
• Unit Conversion Example Problems
• Chemistry Worksheets
• Biology Worksheets
• Periodic Table Worksheets
• Physical Science Worksheets
• Science Lab Worksheets
• My Amazon Books

Elephant Toothpaste – Two Ways to Make It

Elephant toothpaste is a chemical reaction that makes a volcano of foam when soapy water traps gases from the rapid decomposition of hydrogen peroxide. There are two easy methods for making elephant toothpaste. One makes a giant mountain of foam, while the other produces a smaller effect but is safe enough for kids to touch. The dramatic reaction uses strong peroxide and potassium iodide, while the kid-friendly version uses dilute peroxide and replaces potassium iodide with yeast. Here are instructions for both methods and a look at the chemistry involved.

Why Is It Called Elephant Toothpaste?

First, you may wonder why the reaction has the name “elephant toothpaste.” It’s because the thick column of foam escaping a tube looks like toothpaste big enough for an elephant to use. Also, it’s a lot easier and more descriptive than calling the reaction “rapid decomposition of peroxide”. After all, the point of elephant toothpaste is engaging people in the wonder of science. Even if someone doesn’t understand the chemistry, the project is fun and entertaining.

How to Make Giant Elephant Toothpaste

When you see videos of the world’s largest elephant toothpaste, you’re viewing the classic version of the demonstration.

This version uses concentrated hydrogen peroxide, potassium iodide or sodium iodide, liquid dishwashing detergent, water, and (if desired) food coloring:

• 30% hydrogen peroxide (H 2 O 2 )
• Potassium iodide (KI) or sodium iodide (NaI)
• Liquid dishwashing detergent
• Food coloring (optional)
• Large graduated cylinder or Erlenmeyer flask
• Tray or tarp to catch the foam

The chemicals are available online, although it’s easier to just pick up the peroxide at a beauty supply store. Choose any tall container for the demonstration, but use glass and not plastic because the reaction generates heat.

Start by putting on proper safety gear, including safety goggles and gloves.

• First, prepare a saturated solution of potassium iodide or sodium iodide in water. In a beaker, dissolve crystals of either chemical in about 120 ml (4 ounces) of water. Continue stirring in the solid until no more dissolves. It takes about a tablespoon of the dry chemical. But, measurements are not critical here. Set aside the solution for now.
• Set the cylinder or flask in a tray or on a tarp. Pour about 60 ml (2 ounces) of 30% hydrogen peroxide into the glass tube. Add a squirt (about 5 ml) of dishwashing liquid to the tube. If you want colored foam, add a few drops of food coloring. Swirl the liquids to mix them. Here again, exact measurements are unnecessary.
• When you’re ready for the reaction, pour about 15 ml (one tablespoon) of the iodide solution and stand back. Foam forms within seconds and rapidly escapes the tube.
• After the reaction ends, wash the contents of the tray and tube down the drain with water.

Kid-Friendly Elephant Toothpaste

The classic chemistry demonstration is for chemistry educators, but the kid-friendly elephant toothpaste is safe enough for parents and children to perform and touch. Also, this version uses easy-to-find ingredients.

• 3% household peroxide
• 1-2 packet of dry yeast
• Food coloring
• Empty plastic soft drink bottle
• Cookie sheet or pan to catch the foam (optional)

It’s not necessary to don safety gear for this reaction and it’s fine to use either a plastic or glass container. Just make sure the bottle has a narrow opening because this channels the foam and improves the effect.

Don’t worry about measuring ingredients precisely.

• Pour about a cup of 3% hydrogen peroxide into an empty bottle. If the bottle opening is small, use a funnel.
• Add a couple of squirts of dishwashing liquid and a few drops of food coloring to the bottle. Swish the liquid around to mix it.
• In a separate container, mix together yeast with enough warm water that the liquid is easy to pour. A paper cup is a great container choice because you can pinch its rim and make pouring the yeast mixture easier. Wait a couple of minutes before proceeding so the yeast has a chance to activate.
• When you’re ready, place the bottle on a cookie sheet or pan and pour yeast mixture into the bottle
• Clean-up using warm, soapy water.

Is Elephant Toothpaste Safe to Touch?

You can handle the ingredients and the foam from the kid-friendly elephant toothpaste project. However, don’t touch either the ingredients or the foam from the classic giant elephant toothpaste. This is because the peroxide is concentrated enough to cause a chemical burn, while the giant toothpaste is hot enough to cause a thermal burn.

How Elephant Toothpaste Works

The basis for the elephant toothpaste display is the rapid decomposition of hydrogen peroxide (H 2 O 2 ). Hydrogen peroxide naturally decomposes into water and oxygen gas according to this chemical reaction:

2H 2 O 2 (l) → 2H 2 O(l) + O 2 (g)

In a decomposition reaction , a larger molecule breaks down into two or more smaller molecules. The normally slow progression of the reaction is why a bottle of peroxide has a shelf life . Exposure to light accelerates the decomposition, which is why peroxide comes in opaque containers.

Either potassium iodide or the enzyme catalase (found in yeast) acts as a catalyst for the reaction. In other words, either of these chemicals supercharges the reaction so it proceeds very quickly. Breaking chemical bonds in peroxide releases a lot of energy. Only a fraction of this energy goes back into forming chemical bonds making water and oxygen. What this means is that elephant toothpaste is an exothermic reaction or one that releases heat. How hot the reaction gets depends on how much peroxide you start with and how efficiently the catalyst speeds up the reaction. So, the classic version of the project gets hot enough to steam. The kid-friendly version of elephant toothpaste gets warm, but not hot enough to cause a burn.

Producing gas isn’t enough to make a foamy volcano. Adding liquid soap or dishwashing detergent to the mixture traps the gas bubbles. Normally, the reaction doesn’t have much color. Using food coloring makes the foam more interesting. Depending on your choice of colors, it also makes the foam resemble toothpaste.

• Dirren, Glen; Gilbert, George; Juergens, Frederick; Page, Philip; Ramette, Richard; Schreiner, Rodney; Scott, Earle; Testen, May; Williams, Lloyd. (1983).  Chemical Demonstrations: A Handbook for Teachers of Chemistry. Vol. 1.  University of Wisconsin Press. Madison, Wisconsin. doi:10.1021/ed062pA31.2
• “ Elephant’s Toothpaste .”  University of Utah Chemistry Demonstrations . University of Utah.
• Hernando, Franco; Laperuta, Santiago; Kuijl, Jeanine Van; Laurin, Nihuel; Sacks, Federico; Ciolino, Andrés (2017). “Elephant Toothpaste”.  Journal of Chemical Education . 94 (7): 907–910. doi: 10.1021/acs.jchemed.7b00040
• IUPAC (1997). “Chemical decomposition”. Compendium of Chemical Terminology (the “Gold Book”) (2nd ed.). Oxford: Blackwell Scientific Publications. ISBN 0-9678550-9-8. doi: 10.1351/goldbook

Related Posts

• Utility Menu

Harvard Natural Sciences Lecture Demonstrations

1 Oxford St Cambridge MA 02138 Science Center B-08A (617) 495-5824

• Key to Catalog

enter search criteria into the search box

Hydrogen peroxide decomposition by iodide.

30% Hydrogen peroxide in a large round bottom flask decomposes rapidly to hissing steam and oxygen when potassium iodide is added.

[ https://harvard.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=c3f365a2... video of decomposition of hydrogen peroxide by iodide]

What it Shows

When the H 2 O 2 solution is at room temperature, no reaction appears to be happening. But the reaction is just very, very slow. The dramatic effect of a catalyst on the decomposition rate of H 2 O 2 is immediately evident when potassium iodide is added. The color changes also indicate that the KI returns to its original state after the reaction and is not consumed.

Setting it Up

Wear safety goggles and gloves. Keep the audience at a good distance away. Make sure the flask is stable and the mouth is pointed directly up. Make sure there is nothing directly above the opening of the flask. 30% H 2 O 2 is a reactive hazard, and will burn and bleach skin. After the reaction, the flask and solution is hot, contains potassium iodide and water only and is not a hazard.

Demonstrating it:

The 12L Round Bottom Flask is set on white C-Fold towels covering a large cork ring on the lab bench. 100-150 mL of 30% hydrogen peroxide is carefully poured in. The liquid should be visible against the white towels from the perspective of the class, and any camera, if used. The catalyst is 5 g of potassium iodide in a small plastic weighing boat labeled KI.

Put on safety gear. Add the KI in one smooth motion and get back!

When the KI hits the hydrogen peroxide, it changes color to brown as the active catalytic form of the iodide is formed. This shows up well against the white towels. The brown region bubbles and spreads, and rapidly the entire volume of hydrogen peroxide releases oxygen, and then boils up to nearly filling the flask. Hot oxygen and steam shoot out of the mouth of the flask, to the ceiling if you're lucky.

If the instructor wishes, another aliquot of 75 - 100 ml of hydrogen peroxide can be added, to show that the catalyst is still present. The solution turns brown and bubbles, but does not react as vigorously as the first time.

Cleanup and Disposal:

Once the solution is cool to touch, carefully pour it down the drain with lots of water.

Since we use the same 12 L flask, it must be rinsed of all trace of iodide before putting it upside down to drip dry. Store on the large cork ring on the shelf with the neck low to keep dust from settling. A lot of things act as a catalyst for decomposing hydrogen peroxide, so keep that flask clean!

The decomposition reaction taking place is 2H 2 O 2  (aq) --> 2H 2 O (l)    +  O 2  (g) + heat. The reaction is highly exothermic. The KI acts as a catalyst to speed up the reaction rate with the following mechanism:

H 2 O 2  (aq) + I -  (aq) -> OI -  (aq) + H 2 O (l)

H 2 O 2  (aq) + OI -  (aq) -> H 2 O (l) + O 2  (g) + I -  (aq)

There are other notable variations to this hydrogen peroxide decomposition reaction, as well as many different substances that will catalyze the decomposition including potatoes, liver, manganese dioxide, and yeast. Sodium iodide can be substituted for the potassium iodide.

1) Elephant's toothpaste. Always a crowd-pleaser! Click here to watch a video!

2) Genie in the bottle. Mystify your students by rubbing a magic lamp from which steam emerges! Read about it here .

3) Biological catalysts - Enzymes: Catalase in potatoes and liver will speed the decomposition of hydrogen peroxide. Here is a brief description describing these enzyme catalysts.

References and Acknowledgements:

Developed by Daniel Rosenberg, circa ___.

Johnson, Ken (1967) "Chemical Kinetics of KI Catalyzed H2O2 Decomposition," Iowa Science Teachers Journal: Vol. 5: No. 2, Article 12.

Steve Spangler. (2013, August 22). Back to school science elephant’s toothpaste - cool science experiment . YouTube. https://youtu.be/ZbUOPAgJIOQ?feature=shared

Spangler, Steve. (2023, August 17). Genie in a Bottle . https://stevespangler.com/experiments/genie-in-a-bottle/

University of York, Department of Chemistry. (1995, September). Decomposing Hydrogen Peroxide.  https://www.york.ac.uk/chemistry/about/schools/chemrev/projects/peroxide/

Demo Subjects

Newtonian Mechanics Fluid Mechanics Oscillations and Waves Electricity and Magnetism Light and Optics Quantum Physics and Relativity Thermal Physics Condensed Matter Astronomy and Astrophysics Geophysics Chemical Behavior of Matter Mathematical Topics

Key to Catalog Listings

Size : from small [S] (benchtop) to extra large [XL] (most of the hall)  Setup Time : <10 min [t], 10-15 min [t+], >15 min [t++] /span> Rating : from good [★] to wow! [★★★★] or not rated [—] 

Complete key to listings

• 3D Printing

Chemistry Demonstration: Catalytic Decomposition of Hydrogen Peroxide (Elephant’s Toothpaste)

Introduction.

Hydrogen peroxide (H 2 O 2 ) naturally decomposes to produce oxygen and water. However, this process takes a very long time. It may be sped up by the addition of a catalyst. In this experiment, we will use the iodide ion (I – ) present in potassium iodide or sodium iodide as a catalyst to speed up the decomposition of hydrogen peroxide. The reaction is also exothermic, meaning that it releases heat.

The catalyzed reactions are shown below:

H 2 O 2 (aq)  + I – (aq)  –> H 2 O (l)  + IO – (aq)

IO – (aq)  + H 2 O 2 (aq)  –> H 2 O (l)  + O 2 (g)

The overall reaction is as follows:

2 H 2 O 2 (aq)  –> 2 H 2 O (l)  + O 2 (g)

• 30% Hydrogen Peroxide (H 2 O 2 )
• Potassium iodide or Sodium iodide
• Food Coloring
• Liquid dish detergent (Palmolive)
• 1 Liter Graduated Cylinder
• A large basin or tarp to facilitate cleanup
• glowing splint (optional)
• Place the 1 Liter graduated cylinder in the center of the large basin or tarp.
• Pour 50 mL of 30% hydrogen peroxide into the graduated cylinder. Add two to four drops of food coloring. Add a small layer of liquid dish detergent to the mixture.
• Prepare a saturated solution of potassium iodide or sodium iodide by adding an excess of salt to deionized water. The supernate of these solutions is used to carry out the reaction.
• Swirl the contents of the cylinder and quickly add 5 mL of saturated potassium iodide solution before the agitation has subsided. This reaction occurs rapidly, so stand back immediately after adding the potassium or sodium iodide solution.
• The reaction produces water and oxygen gas. The oxygen gas is trapped in the foam bubbles of the soap solution. To test for the presence of oxygen, you can introduce a glowing splint to the graduated cylinder.

This experiment utilizes 30% hydrogen peroxide, which is a strong oxidizing agent (household hydrogen peroxide is typically about 3%). Concentrated hydrogen peroxide can cause burns. Wear latex gloves, safety glasses, and avoid contact with the skin and mucous membranes.

A safer version of this demonstration that utilizes 3% (household) hydrogen peroxide instead of 30% hyrogen peroxide is also available. See reference #2 below.

Disposal of Waste Products

All waste products may be safely disposed of down the drain upon addition of plenty of water.

• Conklin, A.R.; Kessinger, A.  Demonstration of the catalytic decomposition of hydrogen peroxide .  J. Chem. Educ. ,  1996 , 73(9), 838.
• Trujillo, C.A.  A modified demonstration of the catalytic decomposition of hydrogen peroxide .  J. Chem. Educ. ,  2005 , 82(6), 855.
• November 2021
• Announcements
• Uncategorized
• Entries feed
• Comments feed
• WordPress.org

Skip to Content

Other ways to search:

• Events Calendar
• K918: Iodine Clock Class Activity

Introduction

I.   The reaction between iodide and hydrogen peroxide produces triiodide.  The triiodide ions are reduced back to iodide by thiosulfate at a much faster rate, until the thiosulfate is consumed.  Then the triiodide ions form a blue starch-pentaiodide complex, causing the solution to turn from clear to dark.  The initial concentration of iodide and thiosulfate are varied, and using the time it takes for the different solutions to change color, a rate order can be determined (see activity sheet developed by Amy Palmer).

A.                     3 I - (aq) + H 2 O 2 (aq) + 2 H + (aq)   à  I 3 - (aq) + 2 H 2 O (l)

B.                     I 3 - (aq) + 2 S 2 O 3 2- (aq) à 3 I - (aq) + S 4 O 6 2- (aq)

C.                     2 I 3 - (aq) + starch Û blue I 5 - -starch complex + I - (aq)

Reaction B is the fastest until all S 2 O 3 2- is consumed.  I 3 - is consumed as fast as it is produced, preventing the blue I 5 - -starch complex from forming.  When S 2 O 3 2- is gone, reaction C takes over and I 3 - and starch immediately react to form the blue complex.

• Goggles and gloves
• 12 x 100 mL beakers
• 1 L volumetric flask
• 2 x 250 mL volumetric flask
• 150 mL beaker

1.74 g sodium thiosulfate pentahydrate (Na 2 S 2 O 3  · 5H 2 O)

1.0 g starch

100 mL 2.0 M sulfuric acid (H 2 SO 4 )

0.5 M potassium iodide (KI)

100 mL 3% H 2 O 2

Prior to Lecture   (prep time ~  20 min.)

1.    Prepare the following solutions:

• Solution A-1:  0.50 M KI (There is stock 0.5 M KI in demo room) – volume needed is 15 mL total
• Solution A-2:  0.028 M Na 2 S 2 O 3 – 1.74 g Na 2 S 2 O 3  · 5H 2 O in 250 mL
• Solution A-3:  1% starch solution, dissolve 1 g soluble starch in 100 mL of water (beaker is fine), solution will need stirring and some heat to dissolve the starch
• Solution B:  In a 1 L volumetric flask, add 100 mL 2.0 M sulfuric acid (H 2 SO 4 ) and 100 mL 3% H 2 O 2 to get a solution that is 0.20 M in H 2 SO 4 and 0.09 M in H 2 O 2 . This should be made shortly before the demonstration, within 24 hours has been sufficient.

2.    Prepare 12 beakers for the reaction, six solution A and six solution B, to be combined in lecture, according to the chart.  Total volume of each solution is 20 mL, total volume once combined is 40 mL (this is the volume used for concentration calculations)

To Conduct Demonstration:

• Solutions A and B are pre-measured into six beakers each.  (The B beakers are all the same, but it is helpful to label things 1A, 1B, etc)  Set up the beakers in two rows so they can be quickly combined.
• Have students ready to time the reactions.  Begin combining solutions (start with solution 5) by pouring the B beakers into the A beakers and start a timer.  Swirl them to agitate.  The solutions will change colors in the order of: 4b, 1, 2, 3, 4, 5, taking approximately 30 seconds to 2 minutes.  Note that the color change may not be as instantaneous as it’s supposed to be if the solutions aren’t agitated.
• Record the times and determine the rate from the limiting reagent, thiosulfate, as outlined in the activity document.  Sample data set:

Safety and Disposal

Goggles should be worn.  All solutions are sink disposable with plenty of water.

B.Z. Shakhashiri, Chemical Demonstrations Vol. 4 , p.39, 1992 .

(This is adapted from Procedure B)

Acknowldegements

Kristin Boles, spring 2016, Amy Palmer and Laurel Hyde Boni, spring 2015

• K910: Effect of Concentration and Temperature on Rates – Iodine Clock
• K912: Effect of Concentration on Rate Bleach and Green Food Coloring
• K925: Hot Packs vs Hydrogen Balloon
• K950: Catalysis – Copper Penny Catalytic Combustion of Acetone
• K953: Catalysis – CoCl2 Catalyzed Oxidation of Tartaric Acid By H2O2
• K956: Catalysis – MnO2 catalyzed decomposition of H2O2 (“Genie in a Bottle”)
• K959: Catalysis – KI catalyzed decomposition of H2O2 (“Giant Snake”)

 Free A-level and IB Chemistry Notes, Resources and Tutorials 

A2-Level Rates of Reaction

• Rates of Reaction
• Orders of Reaction
• The Rate Equation
• Rate and Mechanisms
• Clock Reactions

Video   Tutorial  Iodine Clock Reaction

Quick Notes  Clock Reactions

• The length of time taken to form a small amount of product is measured.
• A colour change or observation is used to show when this small amount of product has formed.
• Measuring the initial rate of a reaction is difficult because the concentrations of the reactants are constantly changing, meaning the rate of reaction is also changing.

• The thiosulfate ions are instantly converting any iodine molecules formed into iodide ions.
• Iodine molecules will no longer be reacted back to iodide ions by the thiosulfate ions and they can react with the starch (causing colour change).
• This is used to find how long it took to form a specific amount of iodine and give the initial rate of reaction.

Full Notes  Clock Reactions

The initial rate of a reaction refers to how fast a reaction is happening at the very start of the reaction . The rate of a reaction changes as the reaction proceeds, due to changes in the concentrations of the reactants ( see Rates of Reaction ).

To find a rate of a reaction, the change in concentration of a reactant (or product) needs to be measured against time. Finding changes of a concentration during the initial stages of a reaction can be very difficult because the concentration is changing rapidly as the reaction proceeds.

One effective method is to time how long it takes to produce a small amount of product compared to the starting amount of reactants . This means that, although the amount of the reactants is changing, the change is very small compared to the concentration overall – meaning the change to the rate is minimal, enabling us to study the initial rate of the reaction.

In order to determine when a small amount of product has been made, we need a visual indication of some kind – usually an indicator (although sometimes precipitate formation can be used). The problem is indicators can be very sensitive and will often change colour as soon as a product is formed – this is no good as we won’t know exactly how much product has been formed to cause the colour change. The colour change would also happen so fast, we would never be able to time it accurately.

To overcome this, another substance is added to the mixture that reacts with the product from the main reaction. This means that no colour change will occur until all of this substance is used up . By adding a known amount of this ‘new reactant’, we can determine how much product must have been formed from the first reaction by the time a colour change occurs.

This process is called a clock reaction. Clock reactions can be confusing to A-level students, but their idea is actually very simple.

Iodine Clock Reaction

A common example of a clock reaction at A-level Chemistry is the iodine clock reaction.

The basic reaction involves hydrogen peroxide and potassium iodide (in the presence of an acid catalyst).

The hydrogen peroxide oxides the iodide ions and iodine (I 2 ) is formed.

Using a simple starch indicator, we can see when iodine has been formed (starch turns dark blue (blackish) in the presence of iodine ).

However, as we are trying to determine the initial rate of the reaction we also need to time how long it takes to form a specific amount of iodine.

To do this, a known amount of sodium thiosulfate is added. Thiosulfate ions react with iodine to form iodide ions.

Now, every time a molecule of iodine is made in the first reaction, it is instantly converted back into iodide ions by the thiosulfate ions. As long as the thiosulfate ions are reacting with the iodine formed, there will be no colour change to the mixture (as there is no iodine to turn the starch indicator dark blue).

As soon as the thiosulfate in the mixture is used up, however, the iodine formed by reaction one stays as iodine. This means the solution turns dark blue (due to the starch indicator).

The time it takes the solution to change colour is determined by the amount of thiosulfate ions there are at the start. The higher the amount of thiosulfate ions, the longer it will take for the solution to change colour. As we are trying to find the initial rate of reaction, we want the amount of thiosulfate ions to be very small compared to the amount of hydrogen peroxide and iodide ions in the mixture (see above) .

If, for example, one mole of thiosulfate ions is present in the mixture when the hydrogen peroxide and iodide ions are mixed, and it takes 30 seconds for the solution to change colour, this means it has taken 30 seconds to produce 0.5 moles of iodine (the reacting ratio of thiosulfate ions to iodine is 2:1).

We now have a ‘rate of reaction’, as we know how long it took to produce a set amount (0.5 moles) of iodine.

By changing the concentration of hydrogen peroxide or potassium iodide, but keeping the amount of thiosulfate ions the same, we can see how the rate of reaction changes as we change the concentrations of each reactant. This is now just the same as determining a rate equation from reaction data ( see Rate Equation ).

Elephant Toothpaste Chemistry Demonstration

A fun science experiment that looks like pachyderm dental care

Jasper White / Getty Images

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

The dramatic elephant toothpaste chemistry demonstration produces copious amounts of steaming foam that looks like the kind of toothpaste an elephant might use to brush his tusks. To see how to set up this demo and learn the science of the reaction behind it, read on.

Elephant Toothpaste Materials

The chemical reaction in this demonstration is between the hydrogen peroxide and a solution of potassium iodide and dishwashing detergent that captures the gases to make bubbles.

• 50-100 ml of 30% hydrogen peroxide (H 2 O 2 ) solution (Note: This hydrogen peroxide solution is much more concentrated than the kind you'd generally purchase at a pharmacy. You can find 30% peroxide at a beauty supply store, science supply store, or online.)
• Saturated potassium iodide (KI) solution
• Liquid dishwashing detergent
• Food coloring
• 500 mL graduated cylinder
• Splint (optional)

For this demonstration, it's advisable to wear disposable gloves and safety glasses. Since oxygen is involved in this reaction, do not perform this demonstration near an open flame. Also, the reaction is exothermic , producing a fair amount of heat, so do not lean over the graduated cylinder when the solutions are mixed. Leave your gloves on following the demonstration to aid with cleanup. The solution and foam may be rinsed down the drain with water.

Elephant Toothpaste Procedure

• Put on gloves and safety glasses. The iodine from the reaction may stain surfaces so you might want to cover your workspace with an open garbage bag or a layer of paper towels.
• Pour ~50 mL of 30% hydrogen peroxide solution into the graduated cylinder.
• Squirt in a little dishwashing detergent and swirl it around.
• You can place 5-10 drops of food coloring along the wall of the cylinder to make the foam resemble striped toothpaste.
• Add ~10 mL of potassium iodide solution. Do not lean over the cylinder when you do this, as the reaction is very vigorous and you may get splashed or possibly burned by steam.
• You may touch a glowing splint to the foam to relight it, indicating the presence of oxygen.

Variations of the Elephant Toothpaste Demonstration

• You can add 5 grams of starch to the hydrogen peroxide. When the potassium iodide is added, the resulting foam will have light and dark patches from the reaction of some of the starch to form triiodide.
• You can use yeast instead of potassium iodide. Foam is produced more slowly, but you can add a fluorescent dye to this reaction to produce elephant toothpaste that will glow very brightly under a black light .
• You can color the demonstration and make it into an Elephant Toothpaste Christmas Tree for the holidays.
• There's also a kid-friendly version of the elephant toothpaste demo that's safe for little hands.

Elephant Toothpaste Chemistry

The overall equation for this reaction is:

2 H 2 O 2 (aq) → 2 H 2 O(l) + O 2 (g)

However, the decomposition of the hydrogen peroxide into water and oxygen is catalyzed by the iodide ion.

H 2 O 2 (aq) + I - (aq) → OI - (aq) + H 2 O(l)

H 2 O 2 (aq) + OI - (aq) → I - (aq) + H 2 O(l) + O 2 (g)

The dishwashing detergent captures the oxygen as bubbles. Food coloring can color the foam. The heat from this exothermic reaction is such that the foam may steam. If the demonstration is performed using a plastic bottle, you can expect a slight distortion of the bottle due to the heat.

Elephant Toothpaste Experiment Fast Facts

• Materials: 30% hydrogen peroxide, concentrated potassium iodide solution or a packet of dry yeast, liquid dishwashing detergent, food coloring (optional), starch (optional)
• Concepts Illustrated: This demonstration illustrates exothermic reactions, chemical changes, catalysis, and decomposition reactions. Usually, the demo is performed less to discuss the chemistry and more to raise interest in chemistry. It is one of the easiest and most dramatic chemistry demonstrations available.
• Time Required: The reaction is instantaneous. Set-up can be completed in under half an hour.
• Level: The demonstration is suitable for all age groups, particularly to raise interest in science and chemical reactions. Because the hydrogen peroxide is a strong oxidizer and because heat is generated by the reaction, the demonstration is best performed by an experienced science teacher. It should not be performed by unsupervised children.
• Sulfuric Acid and Sugar Demonstration
• Create a Magic Genie in a Bottle Effect (Chemistry)
• 10 Cool Chemistry Experiments
• 10 Amazing Chemical Reactions
• 10 Cool Chemistry Demonstrations for Educators
• Color Change Chemistry Experiments
• How to Do the Color Change Chameleon Chemistry Demonstration
• Interesting High School Chemistry Demonstrations
• How to Perform the Nitrogen Triiodide Chemistry Demonstration
• Valentine's Day Chemistry
• The Blue Bottle Chemistry Demonstration
• Alchemy Experiment: Turning Water Into Liquid Gold
• Halloween Chemistry Demonstrations
• Water - Wine - Milk - Beer Chemistry Demonstration
• How to Do the Barking Dog Chemistry Demonstration
• The Gallium Beating Heart Demonstration

Stack Exchange Network

Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Hydrogen peroxide and potassium iodide reactions

What is the explanation for the two possible reactions of $\ce{H2O2}$ with $\ce{KI}$ in acid media (iodide-catalyzed decomposition of hydrogen peroxide or iodide oxidation by hydrogen peroxide) and what determines the prevalence of one over the other?

It is known that if the hydrogen peroxide is concentrated, the pathway which results in the decomposition of hydrogen peroxide is favored. Otherwise, the iodide oxidation is predominant.

Two well-known chemistry demonstrations (elephant's toothpaste and the iodine clock) rely on these reactions.

The first one involves the decomposition of hydrogen peroxide

$$ \ce{2H2O2 ->[\ce{KI}] 2H2O + O2} $$ which is believed to occur through the following mechanism $$ \ce{H2O2 +I- + H+ -> HOI + H2O} $$ $$ \ce{HOI + H2O2 -> H2O + O2 +I- + H+} \text{(rate-determining step)} $$

On the other hand, the reaction that happens in the iodine clock is $$ \ce{H2O2 + 3 I- + 2 H+ -> I3- + 2H2O} $$

I would like to understand this phenomenon based on thermodynamic or kinetic data, since I could not find an explanation for it.

• reaction-mechanism
• thermodynamics
• home-experiment

• $\begingroup$ related chemistry.stackexchange.com/questions/107884/… $\endgroup$ –  Mithoron Commented Mar 14, 2021 at 1:15
• $\begingroup$ What is the mechanism of the 'clock' reaction? Does it also form $HOI$ initially? What is its (likely) rate-determining step? Assuming that both types of reactions can happen in parallel, what decides which one is prevalent must be kinetics, as far as I can tell. So if you can write the differential expression of the rds of each, you should be able to answer your question. $\endgroup$ –  user6376297 Commented Mar 14, 2021 at 13:07
• $\begingroup$ See: chemistry.stackexchange.com/questions/8857/… ... chemistry.stackexchange.com/questions/61260/… $\endgroup$ –  Nilay Ghosh Commented Apr 8, 2021 at 8:04

Know someone who can answer? Share a link to this question via email , Twitter , or Facebook .

Your answer.

Reminder: Answers generated by artificial intelligence tools are not allowed on Chemistry Stack Exchange. Learn more

Sign up or log in

Post as a guest.

Required, but never shown

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .

Browse other questions tagged reaction-mechanism thermodynamics kinetics home-experiment catalysis or ask your own question .

• Featured on Meta
• Preventing unauthorized automated access to the network
• User activation: Learnings and opportunities
• Join Stack Overflow’s CEO and me for the first Stack IRL Community Event in...

Hot Network Questions

• What causes, and how to avoid, finger numbness?
• I want a smooth orthogonalization process
• Why do (some) LaTeX fonts have separate 8pt and 10pt font files?
• In the absence of an agreement addressing the issue, is there any US law giving a university copyright in an undergraduate student's class paper?
• Is it common in modern classical music for timpani to play chromatic passages?
• Is the Star Trek TNG episode Aquiel inspired by The Thing?
• What is an ellipse in infinite-dimensional spaces?
• Undamaged tire repeatedly deflating
• Is the Earth still capable of massive volcanism, like the kind that caused the formation of the Siberian Traps?
• How do I avoid getting depressed after receiving edits?
• Why does Voyager use consumable hydrazine instead of reaction wheels that only rotate when moving the spacecraft?
• How important exactly is the Base Attack Bonus?
• Purpose of sleeve on sledge hammer handle
• Sticky goo making it hard to open and close the main 200amp breaker
• How can the doctor measure out a dose (dissolved in water) of exactly 10% of a tablet?
• What is the smallest interval between two palindromic times on a 24-hour digital clock?
• Pulling myself up with a pulley attached to myself
• A time-travel short story where the using a time-travel device, its inventor provided an alibi for his future murderer (his wife)
• Does legislation on transgender healthcare affect medical researchers?
• What made scientists think that chemistry is reducible to physics and when did that happen?
• Double 6x6 Beam
• Could you suffocate someone to death with a big enough standing wave?
• \element and \lowercase or \MakeLowercase not working together
• An everyday expression for "to dilute something with two/three/four/etc. times its volume of water"

Your browser is not supported

Sorry but it looks as if your browser is out of date. To get the best experience using our site we recommend that you upgrade or switch browsers.

Find a solution

• Skip to main content
• Skip to navigation

• Back to parent navigation item
• Primary teacher
• Secondary/FE teacher
• Early career or student teacher
• Higher education
• Curriculum support
• Literacy in science teaching
• Periodic table
• Interactive periodic table
• Climate change and sustainability
• Resources shop
• Collections
• Remote teaching support
• Starters for ten
• Screen experiments
• Assessment for learning
• Microscale chemistry
• Faces of chemistry
• Classic chemistry experiments
• Nuffield practical collection
• Anecdotes for chemistry teachers
• On this day in chemistry
• Global experiments
• PhET interactive simulations
• Chemistry vignettes
• Context and problem based learning
• Journal of the month
• Chemistry and art
• Art analysis
• Pigments and colours
• Ancient art: today's technology
• Psychology and art theory
• Art and archaeology
• Artists as chemists
• The physics of restoration and conservation
• Ancient Egyptian art
• Ancient Greek art
• Ancient Roman art
• Classic chemistry demonstrations
• In search of solutions
• In search of more solutions
• Creative problem-solving in chemistry
• Solar spark
• Chemistry for non-specialists
• Health and safety in higher education
• Analytical chemistry introductions
• Exhibition chemistry
• Introductory maths for higher education
• Commercial skills for chemists
• Kitchen chemistry
• Journals how to guides
• Chemistry in health
• Chemistry in sport
• Chemistry in your cupboard
• Chocolate chemistry
• Adnoddau addysgu cemeg Cymraeg
• The chemistry of fireworks
• Festive chemistry
• Education in Chemistry
• Teach Chemistry
• On-demand online
• Live online
• Selected PD articles
• PD for primary teachers
• PD for secondary teachers
• What we offer
• Chartered Science Teacher (CSciTeach)
• Teacher mentoring
• UK Chemistry Olympiad
• Who can enter?
• How does it work?
• Resources and past papers
• Top of the Bench
• Schools' Analyst
• Regional support
• Education coordinators
• RSC Yusuf Hamied Inspirational Science Programme
• RSC Education News
• Supporting teacher training
• Interest groups

• More navigation items

Hydrogen peroxide decomposition using different catalysts

• Four out of five
• No comments

From fresh liver, to powdered manganese, create different catalysts to explore the effervescent world of hydrogen peroxide decomposition 

Your shopping list might look strange, but this practical will be well worth it. Supporting student to understand reaction rates, catalysis, and enzymes.

This experiment should take 5 minutes.

Equipment 

• Eye protection
• Measuring cylinders, 250 cm 3 , x1 for each catalyst
• Large tray for spills
• Hydrogen peroxide solution, 75 cm 3 ,100 vol
• Powdered manganese(IV) oxide (manganese dioxide, MnO 2 ), 0.5 g
• Lead(IV) oxide (lead dioxide, PbO 2 ), 0.5 g
• iron(III) oxide (red iron oxide, Fe 2 O 3 ), 0.5 g
• Potato, 1 cm 3
• Liver, 1 cm 3

Health, safety and technical notes

• Read our standard health and safety guidance .
• Always wear eye protection.
• Hydrogen peroxide is corrosive, see CLEAPSS Hazcard HC050 .
• Manganese oxide is harmful if swallowed or inhaled, see CLEAPSS Hazcard HC060 .
• Lead dioxide is a reproductive toxin, harmful if swallowed or inhaled, a Specific Target Organ Toxin and hazardous to the aquatic environment, see CLEAPSS Hazcard HC056 .
• Avoid contact of the catalysts with aluminium and other metal powders, explosive reactions can occur.

Before the demonstration

• Line up five 250 cm 3 measuring cylinders in a tray.
• Add 75 cm 3 of water to the 75 cm 3 of 100 volume hydrogen peroxide solution to make 150 cm 3 of 50 volume solution.

The demonstration

• Place about 1 cm 3 of washing up liquid into each of the measuring cylinders.
• To each one add the amount of catalyst specified above.
• Then add 25 cm 3 of 50 volume hydrogen peroxide solution to each cylinder. The addition of the catalyst to each cylinder should be done as nearly simultaneously as possible – using two assistants will help.
• Start timing.
• Foam will rise up the cylinders.
• Time how long each foam takes to rise to the top (or other marked point) of the cylinder.
• The foam from the first three cylinders will probably overflow considerably.
• Place a glowing spill in the foam; it will re-light, confirming that the gas produced is oxygen.

The lead dioxide will probably be fastest, followed by manganese dioxide and liver. Potato will be much slower and the iron oxide will barely produce any foam. This order could be affected by the surface areas of the powders.

Some students may believe that the catalysts – especially the oxides – are reactants because hydrogen peroxide is not noticeably decomposing at room temperature.

The teacher could point out the venting cap on the peroxide bottle as an indication of continuous slow decomposition.

Alternatively, s/he could heat a little hydrogen peroxide in a conical flask with a bung and delivery tube, collect the gas over water in a test-tube and test it with a glowing spill to confirm that it is oxygen.

This shows that no other reactant is needed to decompose hydrogen peroxide.

NB: Simply heating 50 volume hydrogen peroxide in a test-tube will not succeed in demonstrating that oxygen is produced. The steam produced will tend to put out a glowing spill. Collecting the gas over water has the effect of condensing the steam. It is also possible to ‘cheat’ by dusting a beaker with a tiny, almost imperceptible, amount of manganese dioxide prior to the demonstration and pouring hydrogen peroxide into it. Bubbles of oxygen will be formed in the beaker.

The reaction is :

2H 2 O 2 (aq) → 2H 2 O(l) + O 2 (g)

This is catalysed by a variety of transition metal compounds and also by peroxidase enzymes found in many living things.

• Repeat the experiment, but heat the liver and the potato pieces for about five minutes in boiling water before use.
• There will be almost no catalytic effect, confirming that the catalyst in these cases is an enzyme that is denatured by heat.
• Investigate the effect of using lumpy or powdered manganese dioxide.
• The powdered oxide will be more effective because of its greater surface area.
• Try using other metal oxides or iron filings as catalysts.
• Animal blood may be used instead of liver if local regulations allow this.
• One teacher suggested measuring the height of the foam over suitable time intervals and plotting a graph.

More resources

Add context and inspire your learners with our short career videos showing how chemistry is making a difference .

Hydrogen peroxide decomposition using different catalysts - teacher notes

Additional information.

This practical is part of our Classic Chemistry Demonstrations  collection.

• 14-16 years
• 16-18 years
• Demonstrations
• Reactions and synthesis
• Rates of reaction

Specification

• Catalysts are substances that speed up chemical reactions but can be recovered chemically unchanged at the end of the reaction.
• (d) catalysts as substances that increase the rate of a reaction while remaining chemically unchanged and that they work by lowering the energy required for a collision to be successful (details of energy profiles are not required)
• (e) characteristics of a catalyst
• 2.3.2 suggest appropriate practical methods to measure the rate of a reaction and collect reliable data (methods limited to measuring a change in mass, gas volume or formation of a precipitate against time) for the reaction of: metals with dilute acid;…
• 2.3.2 suggest appropriate practical methods to measure the rate of a reaction and collect reliable data (methods limited to measuring a change in mass, gas volume or formation of a precipitate against time) for the reaction of: metals with dilute acid…
• Rate of reaction.
• (ii) catalysts.
• Enzymes as catalysts produced by living cells (two examples).
• WS.3.5 Interpreting observations and other data (presented in verbal, diagrammatic, graphical, symbolic or numerical form), including identifying patterns and trends, making inferences and drawing conclusions.
• Catalysts change the rate of chemical reactions but are not used up during the reaction. Different reactions need different catalysts.
• Enzymes act as catalysts in biological systems.
• Factors which affect the rates of chemical reactions include: the concentrations of reactants in solution, the pressure of reacting gases, the surface area of solid reactants, the temperature and the presence of catalysts.
• WS3.5 Interpreting observations and other data (presented in verbal, diagrammatic, graphical, symbolic or numerical form), including identifying patterns and trends, making inferences and drawing conclusions.
• Recall that enzymes act as catalysts in biological systems.
• Describe the characteristics of catalysts and their effect on rates of reaction.
• 3e Interpreting observations and other data (presented in verbal, diagrammatic, graphical, symbolic or numerical form), including identifying patterns and trends, making inferences and drawing conclusions
• 7.6 Describe a catalyst as a substance that speeds up the rate of a reaction without altering the products of the reaction, being itself unchanged chemically and in mass at the end of the reaction
• 7.8 Recall that enzymes are biological catalysts and that enzymes are used in the production of alcoholic drinks
• IaS2.11 in a given context interpret observations and other data (presented in diagrammatic, graphical, symbolic or numerical form) to make inferences and to draw reasoned conclusions, using appropriate scientific vocabulary and terminology to communicat…
• C6.2.4 describe the characteristics of catalysts and their effect on rates of reaction
• C6.2.5 identify catalysts in reactions
• C6.2.14 describe the use of enzymes as catalysts in biological systems and some industrial processes
• C6.2.13 describe the use of enzymes as catalysts in biological systems and some industrial processes
• WS.1.3e interpreting observations and other data
• C5.1f describe the characteristics of catalysts and their effect on rates of reaction
• C5.1i recall that enzymes act as catalysts in biological systems
• C5.2f describe the characteristics of catalysts and their effect on rates of reaction
• C5.2i recall that enzymes act as catalysts in biological systems

Related articles

Help learners master equilibrium and reversible reactions

2024-06-24T06:59:00Z By Emma Owens

Use this poster, fact sheet and storyboard activity to ensure your 14–16 students understand dynamic equilibrium

Non-burning paper: investigate the fire triangle and conditions for combustion

2024-06-10T05:00:00Z By Declan Fleming

Use this reworking of the classic non-burning £5 note demonstration to explore combustion with learners aged 11–16 years

Everything you need to introduce alkenes

2024-06-04T08:22:00Z By Dan Beech

Help your 14–16 learners to master the fundamentals of the reactions of alkenes with these ideas and activities

No comments yet

Only registered users can comment on this article., more experiments.

‘Gold’ coins on a microscale | 14–16 years

By Dorothy Warren and Sandrine Bouchelkia

Practical experiment where learners produce ‘gold’ coins by electroplating a copper coin with zinc, includes follow-up worksheet

Practical potions microscale | 11–14 years

By Kirsty Patterson

Observe chemical changes in this microscale experiment with a spooky twist.

Antibacterial properties of the halogens | 14–18 years

By Kristy Turner

Use this practical to investigate how solutions of the halogens inhibit the growth of bacteria and which is most effective

• Contributors
• Email alerts

Site powered by Webvision Cloud

• Grades 6-12
• School Leaders

Get our mega Halloween worksheets bundle! 👻

Elephant Toothpaste Experiment: How-To Plus Free Worksheet

Heat things up with this larger-than-life science lesson.

Who knew toothpaste could be so fun? While no actual toothpaste is produced, this experiment is an exciting and hands-on way to bring several science lessons to life. You’ll want to use some caution when performing it with kids. Some of the chemicals used can be irritating and the substance produced is hot, so you won’t want to actually brush anyone’s teeth with the foam, as tempting as that may be! Read on to see how to do the Elephant Toothpaste Experiment, and  fill out the form on this page  to grab your free recording sheet.

How does the Elephant Toothpaste Experiment work?

This experiment works through a chemical reaction that results from a catalyst (potassium iodide, aka yeast) being introduced into a mixture of hydrogen peroxide and dish soap. The hydrogen peroxide is decomposed into water and oxygen and the catalyst speeds up the reaction, forcing the oxygen into the soap bubbles. The resulting effect is the substance quickly pouring up and out of the container.

What does the Elephant Toothpaste Experiment teach?

This experiment is a crowd-pleaser, but it also serves to teach kids a lot. The concept of a catalyst speeding up a reaction is demonstrated in an obvious and exciting way as the introduction of the yeast forces the foam to explode up and out of the bottle. It also teaches kids about exothermic reactions as the foam coming out of the bottle is hot. Additionally, kids get to see a decomposition reaction as the rapid decomposition of hydrogen peroxide results in the release of oxygen gas.

Is there an Elephant Toothpaste Experiment video?

This video from teacher Hilary Statum will give you the step-by-step instructions for making your own Elephant Toothpaste.

Materials Needed

To do the experiment, you will need:

• 16-oz. empty plastic soda bottle
• Very warm water
• 3% hydrogen peroxide (6% is better, if available)
• Measuring cups
• Measuring spoons
• Safety glasses
• Safety gloves
• Funnel or measuring cup with a lip
• Food coloring

Our free recording sheet is also helpful— fill out the form on this page to get it!

Elephant Toothpaste Experiment steps:

1. place the bottle on a large tray and put on your safety goggles and gloves., 2. mix 1 tablespoon of yeast into 3 tablespoons of warm water until you achieve a creamy consistency. place in a small cup and set to the side., 3. use a funnel or measuring cup to pour half a cup of hydrogen peroxide into the bottle., 4. add a bit of food coloring. for a solid color, add directly into the bottle. for stripes, squirt it with the pipettes so it trickles down the sides of the inside of the bottle., 5. add approximately 1 tablespoon of dish soap to the hydrogen peroxide., 6. use a funnel or measuring cup to add the yeast mixture to the bottle., 7. step back and watch the explosion, grab our free elephant toothpaste experiment worksheet.

Fill out the form on this page to get your worksheets. The first worksheet asks kids to make a prediction about what they think will happen. They can use the provided spaces to draw or write their predictions and observations. The second worksheet lists questions for students to answer about the experiment.

Additional Reflection Questions

• Why do we add the yeast to the water?
• What do you think would happen if we added more dish soap?
• What do you think would happen if we added more yeast to the mixture?
• What is the liquid that is left in the bottle?
• Describe the reaction that occurs. How long does it last?

Can this experiment be done for a science fair?

Yes! If you want to do the Elephant Toothpaste Experiment for a science fair, we recommend switching up some of the variables. For example: Does the type or shape of the container matter? Does the type of dish soap matter? Does adding more yeast change the reaction? Form a hypothesis about how changing the variables will impact the experiment. Good luck!

Looking for more experiment ideas? Check out our  big list of experiment ideas here.

Plus, be sure to  subscribe to our newsletters  for more articles like this., you might also like.

61 Wet and Wild Outdoor Science Experiments and Activities

The whole world is one big science classroom. Continue Reading

Copyright © 2024. All rights reserved. 5335 Gate Parkway, Jacksonville, FL 32256

Amaze a Science Class With Elephant Toothpaste

Iodine Clock Reaction

Try an at home version of this experiment using a few things you may have in your bathroom medicine cabinet. In may ways this experiment feels almost like magic. Two colorless liquids are mixed together and after a few moments the mixture turns a dark blue color. There are actually a couple of simple chemical reactions going on at the same time to make this “clock reaction” occur. This version of the classic “iodine clock reaction” uses safe household chemicals most people have on hand at home.

What you need:

• distilled water (tap water will work OK as well)
• a couple plastic cups
• 1000 mg vitamin C tablets
• tincture of iodine (2%)
• hydrogen peroxide (3%)
• liquid laundry starch

What to do:

• Make a vitamin C solution by crushing a 1000 mg vitamin C tablet and dissolving it in 2 oz of water. Label this as “vitamin C stock solution”.
• Combine 1 tsp of the vitamin C stock solution with 1 tsp of iodine and 2 oz of water. Label this “solution A”.
• Prepare “solution B” by adding 2 oz of water to 3 tsp of hydrogen peroxide and 1/2 tsp of liquid starch solution.
• Pour solution A into solution B, and pour the resulting solution back into the empty cup to mix them thoroughly. Keep pouring the liquid back and fourth between the cups.

What’s going on?

There are actually two chemical reactions going on at the same time when you combine the solutions. During these reactions two forms of iodine created – the elemental form and the ion form.

In Reaction # 1 iodide ions react with hydrogen peroxide to produce iodine element which is blue in the presence of starch. BUT, before that can actually happen, the Vitamin C quickly reacts and consumes the elemental iodine.

The net result, at least for part of the time is that the solution remains colorless with excess of iodide ions being present. Now after a short time as the reactions keep proceeding in this fashion, the Vitamin C gets gradually used up. Once the Vitamin C is used up, the solution turns blue, because now the iodine element and starch are present.

Safety Precautions

Be careful when working with the iodine – it stains, and it stains really well. Be very careful not to spill any of the solution.

Waste Disposal

Dig deeper into the science behind clock reactions in  this paper  from the Journal of Chemical Education.