For this story, the main purpose is to explore the relationship between temperature and pressure of gases but it may spill over into the concepts of floating and density in older children. It also asks questions about gas being a form of matter that has mass and takes up space. Basically, it revolves around a law developed by French chemist/physicist Jacques Charles in 1787 now known as Charles’ Law. This free selection takes a look at how Charles’ Law explains various mysteries concerning balloons and objects that float in the air. It includes the Table of Contents, Preface, Introduction, and Index.