ACTIVITY

Pukin’ Pumpkin

Brewing Up Some Halloween Chemistry!

| Carolina Staff
| October 2, 2026

Carolina Staff
| October 2, 2026

Introduction

What happens when you combine a carved pumpkin with one of the most popular chemistry demonstrations of all time? A spectacular Halloween eruption of foamy fun!

This pumpkin-themed Elephant Toothpaste activity is the perfect way to add seasonal excitement to your science lessons while exploring chemical reactions, catalysts, and decomposition. Students will love the dramatic results, and you’ll love the meaningful science behind the spectacle.

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Activity Details

Materials

Carved pumpkins
Dishwashing liquid
Green food coloring
Hydrogen peroxide, 30%, 30 mL
Large garbage bag or large tray
Weighing boat or filter paper
2 plastic bottles or large graduated cylinders, 250 to 500 mL
Graduated cylinder, 100 mL
Digital balance
Spatula
Timer
Safety Goggles
Gloves

Overview

Because of water’s unique molecular properties, its observable physical properties impact our daily lives in ways we don’t often notice. This activity provides you with visual and quantitative evidence of the phenomena of adhesion, cohesion, and surface tension in water. You will compare these properties of water for deionized water and deionized water with Dawn dish detergent added to make sense of how water’s polar nature determines its physical properties.

Investigation Question

How does the addition of a catalyst affect reaction rate?

Safety

Hydrogen peroxide at 30% is a very strong oxidizer. It is corrosive to clothing and will cause burns if spilled on the skin. Use appropriate personal protective equipment (PPE), such as gloves, chemical splash goggles, and lab coats or aprons, to avoid contact. Know and follow all federal, state, and local regulations, as well as school district guidelines, for the disposal of laboratory waste.

Standards & NGSS

This activity addresses the following concepts:

HS-PS1-4

Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends on changes in total bond energy.

Science and Engineering Practice—Developing and Using Models

Use reaction-time data and a potential energy diagram to construct a model of catalyzed and uncatalyzed reactions.

Disciplinary Core Idea—Matter and Its Interactions:

Develop a model showing that the release or absorption of energy from a chemical reaction system depends on changes in total bond energy.

Crosscutting Concept—Energy and Matter

Changes of energy and matter in a system can be described in terms of flows into, out of, and within that system.

Activity

Teacher Preparation, Tips and Disposal

Upon completion of this demonstration, rinse and dry the bottles before putting them away. Keep PPE on in case a bottle contains leftover hydrogen peroxide. Unless otherwise prohibited, carefully roll up the foam and catalyst on the trash bag and discard it in the trash.

Make sure the bottles are identical and that students understand both bottles are getting the same amount of the same chemicals. The only difference is the addition of the catalyst.
Dawn dishwashing liquid produces a high volume of bubbles.
Announce for students to get ready to time the reactions. You may want to assign individual students, 2 students per group, or split the room in half so both reactions are timed.
Begin timing as soon as the KI is added.
Announce to students when to stop timing the catalyzed reaction.
Check the uncatalyzed reaction periodically for any evidence of bubbles.

Activity Procedure

Crush any lumps of potassium iodide (KI) into fine crystals with a spatula, and then weigh 1.5 g onto a weighing boat or filter paper.
Lay a large garbage bag flat on a desk, table, or lab bench to protect the demonstration area. A large tray may also be used.
Prepare both bottles or cylinders at the same time. Label one “Uncatalyzed” and the other “Catalyzed.”
Place the plastic bottles or large graduated cylinders in the middle of the carved pumpkin.
Measure 15 mL of 30% hydrogen peroxide and pour it into the bottle or cylinder. Repeat for the second bottle or cylinder.
Add 25 drops of dishwashing liquid to the hydrogen peroxide in both bottles or cylinders.
Swirl the bottles or cylinders to mix the liquid soap and peroxide.
Prepare students to begin timing the reactions as soon as the KI is added to the bottle or cylinder labeled “Catalyzed”.
Quickly add the KI crystals to the bottle or cylinder labeled “Catalyzed” and begin timing.
Observe the oxygen gas as it forms bubbles in the soap, creating a plume of foam that is quickly expelled from the pumpkin.
Stop timing the catalyzed reaction when the foam stops flowing out of the pumpkin.
Direct students to answer the demonstration analysis questions. Check for evidence of a reaction in the uncatalyzed container every 5 minutes until students finish. Stop timing if or when a noticeable volume of bubbles is produced in the uncatalyzed container.

Data and Observations

Reaction	Time (s)	Observations
Uncatalyzed Reaction	Will vary with temperature	May see small bubbles
Catalyzed Reaction	Instantaneous–runs for about 2 minutes	Large amounts of foam spew out of the bottle

Analysis and Discussion

What evidence indicates that a reaction took place?
Bubbles were produced.
Why was dishwashing detergent added to the hydrogen peroxide?
The detergent traps the oxygen bubbles, making a foam that allows the bubbles to be more visible and last longer.
Why was the solid potassium iodide added to one of the bottles?
It serves as a catalyst.
Compare the times for the 2 reactions. Using the time data, write a statement explaining what catalysis is.
When a reaction time is relatively slow and needs to be faster, a catalyst can be added. A catalyst reaction has a shorter reaction time because the addition of a catalyst lowers activation energy. See the explanation of the reaction mechanism below.
Hydrogen peroxide (H₂O₂ ) is stable for at least a year if stored in an airtight opaque container at room temperature. Common in first aid kits, a 3% H₂O₂ solution can be applied to minor cuts and abrasions. When the solution contacts tissue and blood, it rapidly decomposes into water (H₂O) and oxygen gas (O₂).
2H₂O₂(_l ) → 2H₂O(_l ) + O₂(_g )
The oxygen gas creates a foam that lifts and washes contaminants out of the wound. This rapid decomposition can only happen in the presence of a catalyst. In the human body that catalyst is catalase, a biological catalyst in blood and tissue. Catalase can lower the activation energy from 75 kJ/mol to about 8 kJ/mol. In this demonstration, solid potassium iodide (KI) dissolves in aqueous H₂O₂ , forming an aqueous iodide ion (I^–) and catalyzing the reaction of aqueous H₂O₂. The steps of the reaction mechanism are as follows:

The decomposition of hydrogen peroxide is an exothermic reaction. If the uncatalyzed activation energy is about 75 kJ/mol and ΔH = -196.1 kJ/mol, sketch a potential energy diagram for the catalyzed and uncatalyzed reactions. Label the reactions, axes, reactants, products, and activation energy for both reactions.