You've probably noticed that when water gets really cold, it freezes. And you've probably seen steam coming from a pot of boiling water. But do you know why that happens? Do you know how wood burns or what's inside a fire extinguisher? When scientists have questions like these, they conduct experiments to find the answers. Through countless experiments, scientists have learned about different states of mattersolids, liquids, and gasesand what makes matter change from one state to another. Explore the fascinating discoveries scientists have made about the matter we use every day.