To learn about the world around us, we need information. In the practice of science, several methods used to gather that information. Some of the most common methods include:

Understanding chemical and physical changes is a strange part of science. Once you learn to use chemical equations, it is so simple that no one even thinks about it. Before you learn to use chemical equations, it is so complex that most people don't really understand it. For a better view of that, you might also read Changing How We Look at Changing.

This is one of my favorite science demonstrations. It never fails to get people thinking.