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Have you ever wondered how your lungs move air around? Safety: This activity involves using scissors to cut into a plastic bottle. Ask an adult for help with this step and cover the resulting sharp edges with duct tape.

Chemical formulas, such as H2O (water) and CO2 (carbon dioxide), are handy as they identify which atoms are present in a chemical compound. This can in turn help to make predictions about their properties. But only knowing which atoms make up a compound sometimes isn’t enough. It helps to know how the atoms are arranged.