The goal of this activity is to introduce the concepts of solute and solvent, as well as the concepts of saturation and supersaturation. Students explore the former by dissolving packing peanuts (polystyrene) in a concentrated acetone solution. Polystyrene is made up of polymerize units of styrene, and as a result of that polymerization most of the volume of the products that are made of polystyrene, such as packing peanuts, is actually air not polystyrene. This means that when the polystyrene is dissolved in an organic solvent such as acetone, the polymer loses its rigid shape and dramatically decreases is volume. The latter is explored by carefully making a supersaturated sugar water solution using a hot plate. Once the solution is made, it is then cooled. Once the students add a few crystals of sugar to the cooled supersaturated solution, a precipitate forms as the excess sugar comes out of solution.
1. Be able to define solute and solvent
2. Be introduced to the concept of solubility, and that it varies from substance to substance
3. Understand that solubility can be increased with temperature and pressure
4. Be introduced to saturation, unsaturation, and supersaturation
Lesson Materials (view or download)
solubility, saturation, supersaturation
Last updated: 3/4/2015