Rubber Egg

1. Rubber Egg Materials: Pre-soaked egg in vinegar; fresh egg for comparison What you do: Bounce prepared de-shelled egg gently from low height. What students see: Egg feels rubbery and can bounce slightly. Question: Where did the hard shell go? 2. Reusable Hand Warmer Crystallizes Materials: Commercial sodium-acetate click hand warmer What you do: Click metal disk and watch crystallization spread. What students see: Clear liquid turns solid and warm. Question: Why does freezing/crystallizing make heat? 3. Contact-Angle Race Materials: Waxed plastic, glass/plastic sheet, paper; water dropper What you do: Put equal drops on different surfaces. What students see: Drops bead, spread, or soak differently. Question: Why is the same water a different shape on each surface?

Predict → observe three demonstrations → compare what changed → choose independent activity station → cleanup/share. Guiding questions: Question: Where did the hard shell go? Question: Why does freezing/crystallizing make heat? Question: Why is the same water a different shape on each surface?