In this chapter, this story really leaves us hanging! It’s a great one for real investigation! There are two purposes of the story: the first is to investigate closed systems. Anything that happens inside uses up only the materials in the jar, because there is no access to the outside world. The second purpose is for students to understand that air has mass and contains the materials that plants need to make their food and build their structure. I think a further purpose of the story is to allow the students to be puzzled by the outcome, and learn from this puzzlement how to try to find out how things happen.