Is it a liquid or is it a solid? The children made Oobleck today. We mixed corn starch and water until it was almost soupy. The children were amazed that it was solid until they picked it up and then it turned to a liquid. They had so much fun with science today. This was also a sensory activity to help those children who might have sensory issues. This is a fun (and messy) activity to do at home. Since it is just cornstarch, it cleans up easily. This would probably be a good activity to do outside if you don't want to clean the mess.