Why do we burp when we take a swig of a fizzy drink? What are air and water actually made of? And when a liquid raw egg becomes a solid fried egg, can this change of state ever be reversible? Packed with hands-on investigations, this book explores topics including, the properties of solids, liquids, and gases, how liquids become solids and how solids become liquids, how the water cycle works, why seawater is salty, and how changing states make recycling possible. Readers will get the chance to do experiments including discovering if there is water vapour in the classroom around them, separating mixed up substances, and even weighing the air.