Each year, in celebration of the American Chemical Society’s National Chemistry Week, the parents and caregivers who volunteer for the PTO’s STEM Committee host a series of chemistry activities directly after school that revolve around the national event’s theme. This year, Brackett explored the theme “Picture Perfect Chemistry” which explored the science of imaging in some of our experiments.
Monday: Imaging with Thermal Paper
On Monday, kicked off the chemistry of imaging by exploring thermal paper, a special paper that has a coating that changes color when exposed to heat (thermal energy) — no ink is used. One activity station was equipped with a portable laminator, which passes paper through hot rollers (which is normally used to affix laminate onto paper). In our activity, we used thermal paper that was topped with a thin, plastic stencil chosen by students. The (Halloween-themed) stencil shielded parts of the paper from direct heat while allowing other uncovered parts to develop, which left students with an image when it came through the machine.
In our the second station, a thermal printer, which produces a printed image by selectively heating thermal paper when it passes a thermal print head, was connected to an iPad. Via an easy-to-use application, students chose images that were printed on thermal sticker paper.
Tuesday: Color Separation with Paper Chromatography
On Tuesday, we used strips of chromatography paper and water-based markers to explore how colors can be made out of the combination of other colors. By separating the individual dye components within a mixed color like black ink, we reveal the different pigments that were combined to make it. The reason why the colors separate has to do with the chemicals that make up the color (pigments), the water, and the paper; some pigments attach to water better than others so they move further through the paper before sticking.
Wednesday: Fun with Oobleck
Wednesday marked a departure from the imaging theme to bring a fan-favorite to Brackett: Oobleck. A simple mixture of two-parts corn starch to one-part water makes a messy and gloopy suspension that is a non-Newtonian fluid. Newtonian fluids are what we normally think of when we hear the word “fluid” — things like water, milk, juice, honey, and even air. Their viscosity (how fast or slowly something flows) remains constant regardless of pressure applied. Conversely, a non-Newtonian fluid’s viscosity changes depending on the amount of force applied. What does that mean? Brackett students found that if they applied force to the Oobleck by, for example, rolling it in their hands, it acted as a solid and formed a ball. However, if they removed the force by opening their hand, it would act as a liquid and flow out between their fingers. They had a great time alternating between slowly sinking their hands deep into liquid goo or hitting the surface of the Oobleck in the container and finding it a hard solid.
Thursday – DIY Handwarmers
For our last day, students got ready for the upcoming winter by making Do It Yourself Hand Warmers. Students mixed superabsorbent polymer (a material which can absorb up to hundreds of times their weight in water — often used in applications like gardening where they can help soil retain water between waterings), calcium chloride (a salt that we New Englanders might better recognize as a common “ice melt” used after snowstorms), and water. Students discovered that when the calcium chloride dissolved in the water, an exothermic chemical reaction occurred and released energy in the form of heat (which is why calcium chloride works so well to melt ice in the winter). The superabsorbent polymer held the water in a gel so that they didn’t have to carry around a bag of liquid.
