Dentifrice d'Éléphant

Décomposition catalytique rapide du peroxyde d'hydrogène produisant une immense colonne de mousse

Classroom Demonstrations Beginner (Middle School) 20 min ~$10,00

Objectif

Démontrer la décomposition catalytique du peroxyde d'hydrogène avec l'iodure de potassium, illustrant les concepts de catalyse, de réactions exothermiques et de dégagement gazeux.

Contexte

Elephant toothpaste is one of the most popular chemistry demonstrations. Concentrated hydrogen peroxide (H₂O₂) is decomposed rapidly by a potassium iodide (KI) catalyst, releasing oxygen gas and steam. When performed in a narrow-neck flask with dish soap, the oxygen gas creates a towering column of foam that erupts like giant toothpaste. The reaction is exothermic, and the foam is warm to the touch. The iodide ion acts as a catalyst by cycling between I⁻ and IO⁻ intermediates.

Avertissements de sécurité

  • 30% H₂O₂ causes severe skin burns and eye damage
  • Wear face shield and heavy-duty gloves
  • Do not stand over the flask when adding KI
  • The foam is hot — do not touch immediately
  • Perform behind a safety shield

EPI requis

goggles gloves lab_coat face_shield

Matériaux

  • Hydrogen peroxide (30%) (50 mL)
    30% concentration required for dramatic effect
  • Potassium iodide (KI) (10 g)
    Dissolved in 25 mL water
  • Liquid dish soap (15 mL)
  • Food coloring (5 drops)
    Optional, for visual effect
  • Large tray or bin (1)
    To catch overflow

Équipement

Erlenmeyer flask (1 L, narrow neck) Measuring cylinder Safety shield or splash guard Funnel

Procédure

1

Place the Erlenmeyer flask on the large tray. Set up the safety shield.

2 min Ensure audience is at safe distance
2

Carefully pour 50 mL of 30% H₂O₂ into the flask.

2 min 30% H₂O₂ is extremely corrosive
3

Add 15 mL of dish soap and a few drops of food coloring. Swirl gently to mix.

2 min
4

Dissolve 10 g of KI in 25 mL of warm water. Pour this solution into the flask using a funnel and step back immediately.

2 min Step back immediately after adding
5

Observe the rapid evolution of foam. The reaction is complete in seconds. Discuss the role of KI as a catalyst.

5 min
6

After the foam cools, students may touch it (with gloves). It contains only water, oxygen, soap, and KI — no H₂O₂ remains.

5 min Wait until foam is cool

Résultats attendus

A dramatic eruption of warm, colored foam that rises 1–2 meters above the flask. Steam may be visible. The reaction demonstrates catalysis (KI is not consumed), exothermic processes, and gas evolution (O₂).

Nettoyage

The foam is non-toxic (soap, water, KI). Rinse down the drain with plenty of water. Clean the flask and tray.

Détails

Catégorie
Classroom Demonstrations
Difficulté
Beginner (Middle School)
Durée
20 min
Coût estimé
$10,00
Étapes
6
Matériaux
5

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Frequently Asked Questions

What is the objective of Dentifrice d'Éléphant?
Démontrer la décomposition catalytique du peroxyde d'hydrogène avec l'iodure de potassium, illustrant les concepts de catalyse, de réactions exothermiques et de dégagement gazeux.
How difficult is Dentifrice d'Éléphant?
This experiment is rated as Beginner (Middle School). It takes approximately 20 minutes to complete.
What safety precautions are needed for Dentifrice d'Éléphant?
Key safety precautions include: 30% H₂O₂ causes severe skin burns and eye damage; Wear face shield and heavy-duty gloves; Do not stand over the flask when adding KI.
What materials are needed for Dentifrice d'Éléphant?
The main materials required are: Hydrogen peroxide (30%), Potassium iodide (KI), Liquid dish soap, Food coloring, Large tray or bin.
What results should I expect from Dentifrice d'Éléphant?
A dramatic eruption of warm, colored foam that rises 1–2 meters above the flask. Steam may be visible. The reaction demonstrates catalysis (KI is not consumed), exothermic processes, and gas evolution (O₂).