What are some small scientific experiments made of simple materials?

Small scientific experiments of simple materials include experiencing the weather, zero-cost fountains, green plants, eggs with shells, wonderful kaleidoscopes, exploding plastic bags, small volcanoes, water absorption tests, burning words and so on. For example, burning words, the materials are lemon, white paper and candles. Write or draw on the white paper with lemon juice, then dry the paper and bake the white paper with candles. The traces left by lemon appear again. Simple scientific experiments of expansive materials include experiencing the weather, zero-cost fountains, green plants, eggs with shells, wonderful kaleidoscopes, exploding plastic bags, small volcanoes, water absorption tests, burning words and so on. For example, burning words, the materials are lemon, white paper and candles. Write or draw on the white paper with lemon juice, then dry the paper and bake the white paper with candles. The traces left by lemon appear again.