This is a sample project that shows some things that might happen to a water molecule. Press "See inside" to see how the project works. Make sure you understand how the "broadcast" and "when I receive" blocks work to control the backdrop, button, and water molecule sprite. Remix or create your own program to follow the travels of a water molecule through further adventures perhaps in sea ice, traveling through a tree, hitting pollution on city streets, etc...
This is an adaptation of a student starter project from Scratch user bits_and_pieces.