What Is an Exothermic Reaction and How to Observe It with a Simple Experiment

An exothermic reaction is a chemical reaction that releases energy in the form of heat. It is the opposite of an endothermic reaction, which absorbs energy from its surroundings.

🧪 How to Understand an Exothermic Reaction with a Practical Experiment

Below is a very simple experiment that helps explain what an exothermic reaction is in a visual and hands-on way. It is suitable for children, always under adult supervision.

📦 Materials Needed

• 🧲 Steel wool (available at any hardware store).
• 🧪 Vinegar.
• 🥛 Two glass beakers or cups.
• 🧻 A lid or a piece of paper to cover the glass.
• 🌡️ A thermometer.

🔬 Steps to Perform the Experiment

1. Place the steel wool in one glass and soak it in vinegar for about one minute.
2. Remove the steel wool, lightly squeeze out the excess liquid, and place it in the second glass together with the thermometer.
3. Cover the glass, leaving a small opening so you can read the thermometer.
4. Record the temperature for approximately five minutes.

🔥 What Happens During the Reaction

During the experiment, you will notice that the temperature inside the glass gradually increases. In some cases, a slight mist or fog may even appear.

The vinegar removes the protective layer from the steel wool, allowing the iron to react with the oxygen in the air. The oxidation of iron is an exothermic reaction, because it releases energy in the form of heat.

⚗️ Simplified Chemical Equation

2Fe²⁺ (aq) + 1/2 O₂ (g) + 2H₂O → Fe₂O₃ (s) + 4H⁺ (aq)

📋 Summary Table: Exothermic vs. Endothermic Reactions

Content written by the Vilssa editorial team.