As is our end of year tradition, Science for All welcomed students from two of our three partnering schools for 2023-2024 to the UMN-TC campus for days of experiments, lab tours, and interaction with grad students and faculty. Twenty-nine students from Andersen United Middle School visited on Thursday, May 16th, accompanied by teachers Benjamin Winter (SFA partner) and Austen Kruzeski. The very next day, Friday, May 17th, we hosted a whopping 44 students from Murray Middle School, accompanied by teachers Mary Crowley (SFA partner) and Holly, a student teacher working with Mary.
After the students arrived by bus, SFA volunteers escorted them to the Valspar Lab in the basement of Amundson Hall. (Shoutout to Mike Manno for kindly offering this space for SFA’s Field Trip once again!). Daniel (SFA co-president) gave a short overview of the day before Mayank (SFA co-president) and Nhu began the presentation on the first experiment: electrochemistry! From a brief review of atomic structure, they built up the concept of water electrolysis, in which an electric current is used to split water molecules into protons, hydroxide ions, O2, and H2.
Because these species create local pH values at opposite ends of the pH scale, the chemical reactions could be shown by an indicator. Mayank and Nhu then explained the inverse process of using chemical reactions to create electricity through a voltaic pile, in which a reaction between alternating layers of metals separated by an electrolyte can build up a voltage. With this background knowledge, the students got to work. For electrolysis, they used alligator clips to connect the graphite of pencils sharpened at both ends to a 9-V battery and then placed the graphite tips first in water, then in salt water, and finally in salt water with an indicator. The salt water contained ions that helped deliver electrons from the anode to the cathode, making the electrolysis reaction go more quickly and produce lots of bubbles of O2 and H2! Then, with the indicator, the students could see pink color caused by the release of H+ ions at the anode and yellow color by OH- ions at the cathode.
Then, the students transitioned to the voltaic pile experiment. On top of an aluminum foil current collector, they stacked repeated units of copper, electrolyte, and zinc. For an electrolyte, they used small squares of cardboard soaked in lemon juice. As the students stacked higher and higher piles, they measured increasing voltages using voltmeters. With a pile voltage of about 3 V, they were able to light a small LED by touching the leads to the foil and the top of the pile. One group from Murray reached 10 V, certainly an SFA record! Finally, after a few recap trivia questions, Mayank and Nhu illustrated the concept of open and closed circuits through an activity in which the students lit LEDs from the battery using different Play-Doh structures. One group from Andersen made a Play-Doh snail with light-up eyes!
Emma (School Team Leader for Murray) then led the second experiment, focusing on color from fire. Using the example of fireworks, she explained how excited electrons release different amounts of energy depending on their host element, which translates to different colors of light being produced. In typical SFA fashion, she then posed a scientific quest to the students: identify an unknown salt solution mixture using a series of known solutions. By igniting the salts in the solutions, the students could observe which colors came from which salts and then choose which combination they thought best described the mixture. At the experiment tables, students dipped spatulas into vials containing the solutions, and SFA volunteers used the blowtorches to rapidly evaporate the water and ignite the salts on the spatulas, producing brilliantly colored flames - yellow/orange for sodium, red for lithium, purple for potassium, and green for copper. The students then observed their unknown mixtures and tried to identify them based on color. One group from Murray had a disagreement about which two salts were in their unknown, so they took a very scientifically minded approach: they mixed different known solutions and compared them directly to the unknown mixture, ultimately guessing correctly!
After Emma’s experiment, Daniel led the students over to Kolthoff Hall for a tour of the Hillmyer lab, overviewing the instruments he and his group-mates use to create and characterize sustainable polymers. Very hungry at this point, the students then had Jimmy John’s for lunch in the grad lounge back in Amundson Hall. They enjoyed the ping pong table, the white board, and conversations with Professors Matt Neurock and Kim Kosto, who kindly came to talk with the students about their exciting days and share information about UMN. After lunch, the students went back down to the Valspar Lab for a tour of the space. First, Rohan (last year’s co-president) overviewed the 3D printing equipment, and the students enthusiastically played with the various structures printed by UMN students over the last few years. Then, Daniel took over and explained the various pieces of polymer processing equipment in the Valspar Lab, demonstrating an Izod impact strength test on a piece of high-impact polystyrene.
Finally, the volunteers led the students to the pavilion outside Vincent Hall for the day’s final activity: liquid nitrogen experiments! Kristine (Webmaster) explained the idea of freezing substances at cryogenic temperatures and the unusual behaviors that come with it. She showed the students how materials that are stretchy at room temperature, such as rubber bands and balloons, become rigid and brittle after being dipped in the liquid nitrogen. The students then had a chance to dip the objects in themselves, some opting for the pine cones and leaves strewn around the pavilion. By eating cheese balls that had been cooled in the liquid nitrogen, the students channeled their inner dragons as they breathed out wisps of condensation. A separate team of volunteers had been stirring a mixture of dairy ingredients, sugar, and vanilla with liquid nitrogen, and it was soon time to dish out the resultant ice cream! After everyone had gotten a bowl, the volunteers then escorted the students to the front steps of Amundson Hall for a final picture before returning them to the bus and saying goodbye until the fall.
