Lesson 1: Investigation 5: Chromatography

Sticky Question: How Do You Separate Molecules That Are Attracted to One Another?

- SAP-3.B: Represent the relationship between potential energy and distance between atoms, based on factors that influence the interaction strength.

- SPQ-3.C: Explain the relationship between the solubility of ionic and molecular compounds in aqueous and nonaqueous solvents, and the intermolecular interactions between particles.

Students are working for a crime lab and a chemical residue has been turned in for analysis. To identify the chemicals in the residue, they will need to separate them from the mixture and identify them individually. Another lab technologist has made an attempt to separate the molecules but was not as successful as the boss would like. There was only one molecule separated from the mixture, but the boss suspects that there are at least three different molecules. Science is often a process, where a method is tried and then modified for a second attempt. The students’ job will be to propose a modification and attempt to improve the separation attained.

Prior to this lab students will be assessed on the following things to ensure success. Additional supports will be put in place pending the results of that assessment. Students should be able to;
- Use lab equipment to accurately measure volume;
- Measure distance traveled for solvent and associated food dye molecule;
- Identify the relationship between molecular structure and intermolecular forces; and
- Compute a mathematical ratio.

Students will be assessed using the AP Lab scoring criteria.

AP Chemistry Guided Inquiry Investigations: Teacher Manual Updated for Fall 2019