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Boom Goes the Beaker Activity + ward ' s science Recommended Grade Level(s): Appropriate for: Middle School and High School Time Requirements: Activity Time: 15 minutes Teaching Topics & Concepts: • This activity illustrates the concept of conservation of mass • This activity illustrates that gas has mass • This activity introduces students to the concept of empirical evidence Materials: • Hydrogen peroxide, 30%, 5 ml • Potassium iodide, 0.5 g • Dish soap, 1.5 ml • 600 ml glass beaker • Weigh boat or weighing paper • Balance (readability: 0.01 g minimum, capacity: 220 g minimum) • Notebook or other means to record data • Optional: food coloring (a few drops), distilled water (1.5 ml) Safety • Caution when handling 30% hydrogen peroxide, as it is a strong oxidizer and can cause severe irritation and possibly burns to the skin and eyes. Harmful if swallowed or inhaled. ! Background When potassium iodide (KI) is mixed with hydrogen peroxide (H2O2), oxygen gas (O2) is produced, leaving behind water (H2O) and Iodide ions (I-), according to the following two-step reaction process: H2O2 + I- = H2O + OI- H2O2 + OI- = H2O + O2 + I- In addition, since this is an exothermic reaction, heat is generated during the process. Procedure: 1. Weigh out approximately 0.5 g of KI powder, then set aside; record exact weight. (Optional: dissolve the KI powder in distilled water for faster reaction; record weight of KI solution.) 2. Place the glass beaker on the balance, tare to zero, then add 5 ml of H2O2 and 1.5 ml of dish soap; record weight. (Optional: add a few drops of food coloring for a brighter foam.) 3. Add all the KI at once, and watch the total weight decrease as the foam is produced. 4. Record the final weight when the reaction is done (weight stabilizes). 5. Larger volumes can be used for larger demonstrations. For a demonstration of the reaction without recording the weight, larger volumes of materials can be used, and placed into a graduated cylinder instead of a beaker; this will cause the foam to shoot out the top of the cylinder in a snake-like fashion.