Unit 6: Chemical Reactions

Chemists answer questions about what substances are and where they come from. In this unit, students take on the role of student chemists to solve mysteries that can only be solved with an understanding of fundamental chemical principles. The first mystery is a fictional yet realistic scenario in which a reddish-brown substance is coming out of the water pipes in a neighborhood that gets its water from a well. This scenario serves as the anchor phenomenon for the unit. As students learn about what makes substances different in Chapter 1, they apply their growing knowledge of properties and atomic composition to determine that the reddish-brown substance is not the same substance as either the substance that makes up the pipes or the fertilizer that has seeped into the well water. As students learn about chemical reactions in Chapter 2, their explanation builds. Students apply what they have learned about atomic rearrangement to determine that the reddish-brown substance, now identified as rust, could only have formed from a chemical reaction between the iron pipes and the fertilizer. As students learn about the conservation of matter in Chapter 3, their explanation culminates with the conclusion that the reaction between the iron pipes and the fertilizer that formed the rust must also have formed another substance, which must be present in the water. In the last chapter of this unit, students continue in their role as student chemists, working to assist in a police investigation of a robbery that involved the use of an unknown substance to steal a rare and expensive diamond. Students must use their understanding of substances, atoms, and chemical reactions to identify the unknown substance as hydrofluoric acid. They then help the police determine which of their suspects is most likely to have produced this substance.