More than likely, you’re already familiar with redox (reduction-oxidation) chemistry in your daily life. Looking around the home, you’ll find examples readily available. Batteries create electrical current through redox reactions of various metals. (Rechargeable batteries use electricity to reverse the reaction, so they can be used again.) Nails, cheap silverware, and anything else made with iron may show signs of rust – a redox reaction between iron and oxygen. Getting slightly fancier, the same type of reaction causes silver to tarnish, and gives copper that green patina. Bleach destroys stains through a redox process, as do other “oxy-” cleaners. Using peroxide on one’s hair is the same chemistry as well. Back in the kitchen, that apple you sliced earlier is probably turning brown – a redox reaction that you could have prevented had you dipped the exposed edge in a citrus juice (orange, lemon….). The juice contains vitamin C, a well-known anti-oxidant which functions as a barrier, undergoing a redox reaction itself rather than whatever it is covering.
Now, knowing that redox reactions surround you, wouldn’t it be great to set up a few of your own? You can, but since some reactions or ingredients also present the potential for injury, make sure to protect yourself when appropriate, with eye protection, aprons, gloves, or just getting to a safe distance if necessary. Here are a few ideas for you to explore.
#1 Potato Battery
Potato batteries are something of a classic, using the potato as an electrolyte bridge between a pair of electrodes (zinc and copper, traditionally). A small voltage results from oxidation of the zinc and reduction at the copper surface. A single potato is usually enough for a minimal application like an LED display clock. For more voltage, a number of potatoes can be connected in series. For a quick visual, enjoy this young scientist as he builds a two-potato system. With enough potatoes, anything is possible. Just see what five hundred spuds can do here.
#2 Burning Marshmallows
Fire (combustion) is always a redox process. The fuel is oxidized, oxygen from the air (and the fuel itself, if oxygen is a part of its formula) is reduced. Marshmallows are mainly sugar and air (with gelatin and whatever additives get thrown in). Sugar is a fantastic fuel (it gives human a lot of their energy for that matter), containing a good deal of oxygen to begin with, and the puffed nature of the marshmallow ensures that there is oxygen readily available throughout as well. As a result, one the burning gets started, the reaction is hard to stop. The marshmallow will burn nearly to completion, expanding significantly in the process as the molten mallow is inflated with pockets of carbon dioxide and steam (products of the reaction). A word of caution – do not drop the melty mallow onto the carpet, your mother/wife/landlord will come for your head.
#3 Hollow Penny
Modern U.S. pennies are a thin layer of copper over a core of zinc. Zinc undergoes a redox reaction with hydrochloric acid – the zinc is oxidized to zinc ions (now in solution with the chloride ions) and the hydrogen ions from the acid are reduced to hydrogen gas, which bubbles away. The experiment is easy – just barely scratch a penny along an edge to expose the zinc (if you’re impatient, scratch two or three places) and drop it into a glass or plastic container of the acid. When the bubbling is done, there will be no zinc left, just a thin copper shell.
NOTE: Hydrochloric acid is also known as muriatic acid – available from retailers of pool supplies, and it is also a common drain cleaner – just read the labels.
SAFETY NOTE: Hydrochloric acid is dangerous, wear protection for your eyes and skin. If it does get on you, immediately rinse with cold water for a good ten minutes to avoid burns. It also gives off nasty fumes that will burn if you breathe them, so use it outdoors, or in a ventilated place with lots of air flow.
LEGAL NOTE: It is illegal to destroy American currency. (Unfortunately, Canadian pennies have a different composition.)
#4 More Fun With Acid
Since you’ve already got the acid, and you’ve learned that it gives off noxious fumes, try putting them to work for you. Take a glass container and fill it about a third full with hydrochloric acid. To keep the vapors in, cover it with a piece of aluminum foil. Place the covered container somewhere ventilated, and wait. (You can walk away for a bit if you want, but please label the thing “Danger – Acid” first.) After a while, the vapors eat their way through the foil (oxidizing it) much the same as happened to the core of the penny.
SAFETY NOTE: See #3, and also use care when handling the foil afterwards, as it may have acid on it.
#5 Glowing Mountain Dew
Remember that peroxide is an excellent oxidizer? Did you know that glowsticks are typically made with peroxide? And did you ever notice that Mountain Dew looked pretty fluorescent to begin with? Combining all this knowledge, someone cleverly came up with a recipe using a little of “The Dew”, a pinch of baking soda, and some regular hydrogen peroxide from the first-aid cabinet. It’s a redox reaction all right, but you’ll be too excited to stop and think about that until afterwards. (You may never drink the stuff again.) Follow the link for the “instructional video”.
