Create instant Halloween fun with some zipper bags, food coloring and wooden skewers!
Plastics are polymers (long chains of molecules, like beads on a string.) Some polymers, like the ones in plastic bags, are good at stretching and forming seals. When you poke your skewer through the bag, the plastic forms a seal so it doesn’t leak. The forces of surface tension are also at work to keep the bag from dripping where you’ve pierced it, since water molecules really like to stick together.