Sheldon, Leonard, Howard, and Raj create an oobleck using corn starch and water. Initially, it's a liquid, but when they turn the music on, it resembles a solid. Sheldon explains the phenomenon to Penny: it's a non-Newtonian fluid which is liquid but becomes solid due to the percussion from the speaker.
Professor Philip Brainard creates Flubber and tries to learn more about it. He performs quick tests on the physical properties of Flubber and finds that it is a highly viscous elastomer that can also phase shift between a liquid and a solid. Using observation skills, he also learns that Flubber is moldable, foldable, ductile, and elastic, among other properties.