11 Chemical Reaction Videos, Explained

Each minute, a whopping 100 hours worth of videos are uploaded to YouTube—and a small, yet endlessly fascinating number of those are chemical reaction videos. To explain what exactly is happening in some of these videos we reached out to an expert at the American Chemical Society, John M. Malin, Ph.D, to let us in on some of these awesome chemistry secrets.

1. Ignited ammonium dichromate

No, this chemical reaction isn't "opening a portal to hell," as you may have seen it described on Facebook or other social media sites. A compound known as ammonium dichromate (which was actually used in the early days of photography to capture images) is ignited with a lighter, which reacts by forming a greenish/black powder and producing nitrogen gas. “The exothermic reaction (aka, any chemical reaction that produces heat, light, or sound) produces heat and sparks until the dichromate is used up,” Dr. Malin says. But that’s not all: As a little surprise at the bottom, “demonstrators have evidently placed some mercuric thiocyanate which also reacts when ignited to form the snake-like tendrils shown coming up through the ‘volcano.’” We’ll see this again below. Also, bonus points for the unseen kids yelling “Kraken!”

2. Pharoah’s Serpent

This reaction, called “Pharoah’s Serpent,” is created by burning bits of mercuric thiocyanate, the same compound that produced the Kraken-like tendrils in the experiment above. The tendrils are a byproduct of the ignition, and are made from a resulting compound called carbon nitride. But be warned: If you get your hands on mercuric thiocyanate, don't burn it just anywhere; the demonstrations here and above include highly toxic materials and the reactions they produce are extremely poisonous. These experiments “should only be done in a fume hood,” Dr. Malin says.

3. Elephant’s Toothpaste

Do all chemical reactions have funny names? In this one, known as the “Elephant’s Toothpaste,” hydrogen peroxide rapidly decomposes and produces a foam substance. First, the hydrogen peroxide is mixed with liquid soap or dishwashing detergent, then an iodide salt is added to catalyze and decompose the hydrogen peroxide very quickly, creating a large amount of oxygen and water. The soap causes the oxygen and water to bubble, which makes the foam. To spiff up the experiment, food coloring was added above to give the foam an orange tinge.

4. Iodine Clock

This video gives you the steps and the items you need to do make the “Iodine Clock” reaction, but here's what's happening on a molecular level: A sulfite ion compound (which loses an electron) reacts to an iodate ion (which accepts the lost electron), creating the important-sounding triiodide ion (fancy-talk for an ion with three iodine atoms). Starch is added, which gets rid of the sulfite and produces the dark purple color. Adding sulfite back then makes the purplish iodine turn back into compound iodide, making the color go away.

5. Coke and Milk

You take some Coke, you take some milk, you wait six hours and what do you get? A weird orangey mush! “Milk contains the protein casein which, upon acidification, slides out of the solution to form a viscous, gooey substance,” Dr. Malin says. When you let the Coke-Milk mixture sit for six hours, the casein sinks to the bottom of the bottle, absorbing most of the brown coloring in the Coca-Cola and making the remaining liquid the amber color seen in the video.

6. Black Snake 

Concentrated sulfuric acid is a pretty effective dehydrating agent. If you add it directly to normal table sugar, Dr. Malin says, “it rips the water molecules right out of the carbohydrate,” leaving only carbon left. The reaction makes the carbon expand, which produces the weird-looking black substance seen above.

7. Purple Smoke

This experiment is good if you need to make some kind of ninja smoke-screen escape—but you’ll probably need a lot of powdered iodine to do it. This one works very similar to the reaction seen in #4: the powdered iodine is an oxidant (it accepts electrons in a reaction), while powdered metallic zinc is a reductant (it loses an electron in a reaction). By adding a drop of water to both, it helps initiate contact between the two, which produces the chemical compound zinc iodide. The quick reaction produces a lot of heat, and the heat vaporizes the iodine in the compound, which produces the purple vapor.

8. Hydrogen Peroxide + Blood

Any squeamish readers out there, look away now, and any chemistry nerds out there take notice! In this video, a kooky Russian chemist who calls himself the “Crazy Russian Hacker” drops pig blood into hydrogen peroxide with some bubbly results. The blood is acting as a catalyst for the breakdown of the hydrogen peroxide, essentially speeding up the process due to the iron in the blood’s hemoglobin (a protein that transports oxygen in the blood). According to Dr. Malin, “The reaction produces oxygen molecules and water,” and “the foam is due to oxygen bubbles forming in the blood/water emulsion.”

9. Superabsorbent Polymer

“Super absorbent polymers (SAPs) can absorb as much as 300 times their weight in water,” Dr. Malin says. In this case, the SAP is sodium polyacrylate, a substance used by plumbers to unclog toilets that can also be used in disposable diapers. Add some food coloring to water and then throw in an SAP and the result is a pseudo-solid with a squishy texture.

10. Fake Snow

If you’re stuck in a tropical climate and need a DIY way to create some powder, the super absorbent polymer from the previous post might be your best bet. Make sure to add more sodium polyacrylate to water, which makes it more powdery, and this time you don’t have to include any food coloring. The only drawback is that this “snow” is room temperature.

11. Non-Newtonian Fluid

This one is my personal favorite. According to Dr. Malin, “mixing corn starch and water forms a non-Newtonian fluid, i.e., a fluid that becomes more viscous (gets stiffer) when it is agitated.” The video above shows that agitation in the form of different sound frequencies played through a speaker cone, which forces the non-Newtonian fluid (which are named after Isaac himself because  of how they seem to violate his laws) to stiffen and localize in certain places, thus making it stand up depending on where the sound waves were the strongest.

Illustration by Mental Floss / Images: iStock
The Body
10 Facts About the Appendix
Illustration by Mental Floss / Images: iStock
Illustration by Mental Floss / Images: iStock

Despite some 500 years of study, the appendix might be one of the least understood structures in the human body. Here's what we know about this mysterious organ.


The human appendix is small, tube-shaped, and squishy, giving ancient Egyptians, who encountered it when preparing bodies for funerary rites, the impression of a worm. Even today, some medical texts refer to the organ as vermiform—Latin for "worm-like."


The earliest description of a human appendix was written by the Renaissance physician-anatomist Jacopo Berengario da Carpi in 1521. But before that, Leonardo da Vinci is believed to drawn the first depiction of the organ in his anatomical drawings in 1492. Leonardo claimed to have dissected 30 human corpses in his effort to understand the way the body worked from mechanical and physiological perspectives.


The appendix is a small pouch connected to the cecum—the beginning of the large intestine in the lower right-hand corner of your abdomen. The cecum’s job is to receive undigested food from the small intestine, absorb fluids and salts that remain after food is digested, and mix them with mucus for easier elimination; according to Mohamad Abouzeid, M.D., assistant professor and attending surgeon at NYU Langone Medical Center, the cecum and appendix have similar tissue structures.


The appendix has an ill-deserved reputation as a vestigial organ—meaning that it allegedly evolved without a detectable function—and we can blame Charles Darwin for that. In the mid-19th century, the appendix had been identified only in humans and great apes. Darwin thought that our earlier ancestors ate mostly plants, and thus needed a large cecum in which to break down the tough fibers. He hypothesized that over time, apes and humans evolved to eat a more varied and easier-to-digest diet, and the cecum shrank accordingly. The appendix itself, Darwin believed, emerged from the folds of the wizened cecum without its own special purpose.


The proximity and tissue similarities between the cecum and appendix suggest that the latter plays a part in the digestive process. But there’s one noticeable difference in the appendix that you can see only under a microscope. “[The appendix] has a high concentration of the immune cells within its walls,” Abouzeid tells Mental Floss.

Recent research into the appendix's connection to the immune system has suggested a few theories. In a 2015 study in Nature Immunology, Australian researchers discovered that a type of immune cells called innate lymphoid cells (ILCs) proliferate in the appendix and seem to encourage the repopulation of symbiotic bacteria in the gut. This action may help the gut recover from infections, which tend to wipe out fluids, nutrients, and good bacteria.

For a 2013 study examining the evolutionary rationale for the appendix in mammal species, researchers at Midwestern University and Duke University Medical Center concluded that the organ evolved at least 32 times among different lineages, but not in response to dietary or environmental factors.

The same researchers analyzed 533 mammal species for a 2017 study and found that those with appendices had more lymphatic (immune) tissue in the cecum. That suggests that the nearby appendix could serve as "a secondary immune organ," the researchers said in a statement. "Lymphatic tissue can also stimulate growth of some types of beneficial gut bacteria, providing further evidence that the appendix may serve as a 'safe house' for helpful gut bacteria." This good bacteria may help to replenish healthy flora in the gut after infection or illness.


For such a tiny organ, the appendix gets infected easily. According to Abouzeid, appendicitis occurs when the appendix gets plugged by hardened feces (called a fecalith or appendicolith), too much mucus, or the buildup of immune cells after a viral or bacterial infection. In the United States, the lifetime risk of getting appendicitis is one in 15, and incidence in newly developed countries is rising. It's most common in young adults, and most dangerous in the elderly.

When infected, the appendix swells up as pus fills its interior cavity. It can grow several times larger than its average 3-inch size: One inflamed appendix removed from a British man in 2004 measured just over 8 inches, while another specimen, reported in 2007 in the Journal of Clinical Pathology, measured 8.6 inches. People with appendicitis might feel generalized pain around the bellybutton that localizes on the right side of the abdomen, and experience nausea or vomiting, fever, or body aches. Some people also get diarrhea.


Treatment for appendicitis can go two ways: appendectomy, a.k.a. surgical removal of the appendix, or a first line of antibiotics to treat the underlying infection. Appendectomies are more than 99 percent effective against recurring infection, since the organ itself is removed. (There have been cases of "stump appendicitis," where an incompletely removed appendix becomes infected, which often require further surgery.)

Studies show that antibiotics produce about a 72 percent initial success rate. “However, if you follow these patients out for about a year, they often get recurrent appendicitis,” Abouzeid says. One 2017 study in the World Journal of Surgery followed 710 appendicitis patients for a year after antibiotic treatment and found a 26.5 percent recurrence rate for subsequent infections.


You might imagine a ruptured appendix, known formally as a perforation, being akin to the "chestbuster" scene in Alien. Abouzeid says it's not quite that dramatic, though it can be dangerous. When the appendix gets clogged, pressure builds inside the cavity of the appendix, called the lumen. That chokes off blood supply to certain tissues. “The tissue dies off and falls apart, and you get perforation,” Abouzeid says. But rather than exploding, the organ leaks fluids that can infect other tissues.

A burst appendix is a medical emergency. Sometimes the body can contain the infection in an abscess, Abouzeid says, which may be identified through CT scans or X-rays and treated with IV antibiotics. But if the infection is left untreated, it can spread to other parts of the abdomen, a serious condition called peritonitis. At that point, the infection can become life-threatening.


In 1894, Charles McBurney, a surgeon at New York's Roosevelt Hospital, popularized an open-cavity, muscle-splitting technique [PDF] to remove an infected appendix, which is now called an open appendectomy. Surgeons continued to use McBurney's method until the advent of laparoscopic surgery, a less invasive method in which the doctor makes small cuts in the patient's abdomen and threads a thin tube with a camera and surgical tools into the incisions. The appendix is removed through one of those incisions, which are usually less than an inch in length.

The first laparoscopic appendectomies were performed by German physician Kurt Semm in the early 1980s. Since then, laparoscopic appendectomies have become the standard treatment for uncomplicated appendicitis. For more serious infections, open appendectomies are still performed.


When the future King Edward VII of Great Britain came down with appendicitis (or "perityphlitis," as it was called back then) in June 1902, mortality rates for the disease were as high as 26 percent. It was about two weeks before his scheduled coronation on June 26, 1902, and Edward resisted having an appendectomy, which was then a relatively new procedure. But surgeon and appendicitis expert Frederick Treves made clear that Edward would probably die without it. Treves drained Edward's infected abscess, without removing the organ, at Buckingham Palace; Edward recovered and was crowned on August 9, 1902.


On August 26, 2006, during an autopsy at a Zagreb, Croatia hospital, surgeons obtained a 10.24-inch appendix from 72-year-old Safranco August. The deceased currently holds the Guinness World Record for "largest appendix removed."

Science Has a Good Explanation For Why You Can't Resist That Doughnut

Unless you’re one of those rare people who doesn’t like sweets, the lure of a glazed or powdered doughnut is often too powerful to resist. The next time you succumb to that second or third Boston cream, don’t blame it on weak willpower—blame it on your brain.

As the New Scientist reports, a Yale University study published in the journal Cell Metabolism provides new evidence that foods rich in both carbohydrates and fats fire up the brain’s reward center more than most foods. For the study, volunteers were shown pictures of carb-heavy foods (like candy), fatty foods (like cheese), and foods high in both (like doughnuts). They were then asked to bid money on the food they wanted to eat most, all while researchers measured their brain activity.

Not only were volunteers willing to pay more for doughnuts and similar foods, but foods high in carbs and fat also sparked far more activity in the striatum, the area of the brain where dopamine is released. (Chocolate is one of the foods most commonly associated with increases in dopamine, working in the same way as drugs like cocaine and amphetamines.)

Presented with these findings, researcher Dana Small theorized that the brain may have separate systems to assess fats and carbs. Modern junk foods that activate both systems at once may trigger a larger release of dopamine as a result.

This study doesn’t entirely explain why different people crave different foods, though. Much of it has to do with our habits and the foods we repeatedly gravitate towards when we want to feel happy or alleviate stress. Another study from 2015 found that certain treats associated with high levels of reward in the brain—like pizza, chocolate, chips, and cookies—were considered to be the most addictive foods (doughnuts didn’t make the top 20, though).

It's still possible to turn down foods that are bad for you, though. While many people try to improve their self-control, one of the most effective ways to avoid an undesired outcome is to remove the temptation completely. Free doughnuts in the break room? Stay far away.

[h/t New Scientist]


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