February visit on February 3, 2023
Experiment leaders: Zachary Gdowski and Emily Hoffmann
In February, the Science for All (SFA) graduate student mentors planned two experiments related to mixtures, solutions, and the reactions that can occur within them. First, we gave a presentation to students introducing the difference between mixtures, solutions, and various other chemical states. The presentation included a review of what constitutes atoms, compounds, and then focused on mixtures and solutions, as well as the role that density and viscosity play in them.
The first experiment revolved around creating “oobleck,” a common home science experiment where cornstarch and water are mixed to form a complex fluid. Students experimented with different ratios of the two components and its resulting effects on the flow behavior of the oobleck. They attempted to pour oobleck out of plastic bags and examined the time it took for oobleck to spread across the plate, leading to discussions with the mentors about viscosity, density, and material properties.
The second half of the visit began with a second brief presentation, this time about acids and bases. The presentation introduced the concept of pH and noted many common household items that are acids or bases, such as lemon juice, vinegar, and bleach. The corresponding experiment involved making lava lamps. Students began by creating a mixture of canola oil and water, which provided a good opportunity to reiterate the concept of density. Next, Alka-Seltzer tablets were placed in the lava lamp, causing bubbles to form in the water phase and move into the oil phase. Students experimented with changing the amount Alka-Seltzer added as well as the form with which it was added (crushed vs. whole). Finally, a demonstration was given at each group with baking soda and vinegar in the lava lamp, which caused a more aggressive reaction.
Both experiments ran very smoothly, with great student engagement. The students loved getting their hands dirty with the oobleck and had a fun time creating the bubbling lava lamps, all while learning about relevant scientific concepts!