Everyone loves those science projects we completed in grade school, like making a potato battery or even the classic erupting volcano. However, now that we are all grown up, let’s take a look at how exactly some of the most popular science projects work through the lenses of science.
You can make a battery with lemons, oranges, or other fruits, but there is nothing as quintessential as a potato battery. The potato battery is classified as an electrochemical cell, which converts chemical energy into electric energy through electron transfer. As you likely know, potato batteries and other fruit batteries require a copper cathode and zinc anode. By sticking the copper and zinc inside of the potato but apart from each other, you are facilitating a redox (reduction-oxidation) reaction between the zinc and the copper.
The electricity doesn’t actually come from the potato, rather the water and electrolytes in the spud allow electrons from the copper to move to the zinc, creating small electric currents. In this reaction, the copper is being reduced, thus the shed of electrons, and the zinc is being oxidized. The way a potato battery works is, on premise, the same way all electrochemical batteries store and release electricity.
Glow in the Dark Drinks
Making your drink glow is another fun science experiment, or maybe just a neat party trick. Tonic water is key to this experiment, and when you add this carbonated liquid to a drink, it will glow under ultraviolet light. At the core of this reaction is a chemical known as quinine, which is actually a medicine used to treat malaria. The FDA limits the quinine content in tonic water in the US to 83 parts per million (ppm) to avoid any adverse health effects from the chemical. Due to the structure of the quinine molecules, as UV light hits the quinine, it is absorbed, and visible light is emitted. There isn’t actually any energy transfer in the reaction, rather the light energy is converted from UV light to visible light, usually blue in the case of tonic water.
The Erupting Volcano
A baking soda and vinegar volcano is the essence of the grade school science fair and also the bane of high school janitors. Apart from the fact that the volcano project is actually nothing like an actual volcano, the experiment is actually a good one to teach the fundamentals of chemistry. Vinegar and baking soda are usually used in the reaction, although hot water can be substituted for the vinegar. Baking soda is sodium bicarbonate (NaHCO3), and vinegar is acetic acid (C2H4O2). When they are combined, they produce and acid-base reaction with the bi-product of CO2 or carbon dioxide. For those of you interested in the actual chemical reaction taking place, you can check that out below:
C2H4O2 + NaHCO3 = NaC2H3O2 + H2O + CO2
The outcome of the acid-base reaction is sodium acetate (NaC2H3O2), water, and gaseous carbon dioxide, which is what makes the bubbles and foam. Many projects will use dish soap to increase the surface tension of the bubbles to create an even bigger eruption. All in the name of science, of course.
Non-newtonian fluids are incredibly fun to play with, no matter how old you are. The ability for something to exist in a solid state under high stress and exist as a liquid under low stress is intriguing to our brains, even when we understand what is going on. The most common non-Newtonian fluid is something called oobleck (yes, that is the actual name) which is made from cornstarch (C27H48O20) and water. When the cornstarch is mixed with the water, it becomes a goopy, slimy mess with some interesting properties. When you hit, or even run across, the fluid, the molecules of the cornstarch rigidly align and present low strain. When the stress is implied over a longer period of time, the fluid responds exactly like any other viscous fluid would. Taking these principles further, placing a non-Newtonian fluid on a speaker produces what is known as a dancing liquid. The vibrations in the speaker apply a stress at a high enough rate to engage the rigidity of the cornstarch molecules, and just as they start to convert back to a fluid phase, the speaker creates another vibration. This period of actions and reactions create a, well, dancing liquid.