One of the best divulgers of history, said that “when you are in love, you want to tell the world about it”. That was his leitmotif to explain science in Cosmos, to make it known to the general public. Because, above all, he was passionate about research.
Science not only improves our lives. It is also capable of surprising us, of making us dream of a better future. It is capable of amusing us by understanding what magnetism is. And especially, to leave us with our mouths open with spectacular experiments in chemistry:
The snake of the pharaoh
Who knew that a chemical reaction could give us a curious snake like that of the pharaohs of ancient Egypt? The responsible is mercury thiocyanate (Hg(SCN)2), an inorganic compound in the form of a white powder. When it is heated, an exothermic reaction is produced (which gives off heat), used in the past in pyrotechnics. The result is unbelievable:
In 1821, the scientist Wöhler discovers this curious experiment. If we heat mercury thiocyanate, we cause its decomposition into a solid mass, insoluble in water, composed mainly of carbon nitride (C3N4). The reaction, however, also produces dangerous toxic gases (such as sulphur dioxide), so we should not repeat it at home.
The chameleon’s reaction
The chameleon is a reptile known for its spectacular techniques of camouflage through color changes. In our compilation of chemistry experiments, we could not miss a reaction that, in a certain way, mimics the behavior of this living being.
The so-called chameleon reaction allows us to distinguish, from different colour changes, the variation in the oxidation states of manganese. The experiment is based on initially mixing water, sodium hydroxide (better known as caustic soda) and sugar (sucrose).
By adding sodium permanganate, we will see the different colour changes: violet (MnO4- ions), blue (MnO4 3- ions), green (MnO4 2- ions) and orange (Mn 3+ ions). Each chromatic modification indicates that we have changed the oxidation state of the initial chemical compound, as if it were a real chameleon.
The incredible volcano
When ammonium dichromate ((NH4)2Cr2O7) decomposes at high temperatures, it produces chromium (III) oxide, nitrogen and water. On a practical level, as we see in the following video, we can use orange crystals of ammonium dichromate, which will auto-oxidize and then reduce. How does the reaction happen?
In the formation of the chemical volcano, as explained from the Complutense University of Madrid, the chromium oxide (III) that is formed, leaves the center of the small orange mountain. As it is deposited on the edge, it grows to form a kind of crater.
Why do we see orange flames? The explanation is simple: the temperature is so high that it produces incandescence. The greenish solid mass that we see at the end of the experiment is Cr2O3, characterized by being a little dense, spongy and have a much larger volume than the initial orange crystals.
Toothpaste for elephants
As far as we know, elephants don’t brush their teeth. However, chemistry experiments give us the opportunity to make them a special toothpaste. How? The decomposition of hydrogen peroxide (better known as hydrogen peroxide), thanks to the action of the catalyst potassium iodide, allows us to recreate the toothpaste that any elephant would use.
In the mixture we also use detergent, which will serve to trap the oxygen that is formed and create large amounts of foam. The decomposition of hydrogen peroxide occurs very quickly, resulting in oxygen and water. The experiment we see is also exothermic, so the resulting foam will be at high temperatures.
A pumpkin as terrifying as it is colorful
Although there is still time for Halloween to arrive, we can liven up the wait by trying a chemical reaction that is less flashy. If we prepare a pumpkin like the classics of that party, we can spray it with hand sanitizer (which always contains some kind of alcohol, such as isopropyl, ethyl or propyl) to get a blue flare.
What if we wanted to change color? The pumpkin itself has sodium, so it’s not uncommon to see a yellow flame burning. Using chemistry we can even achieve a green flame (by boric acid), orange (with calcium chloride) or red (by mixing strontium nitrate with potassium nitrate or potassium perchlorate), as explained by chemistry Anne Helmenstine.
The chemistry experiments are certainly spectacular. As Sagan would say, seeing the different reactions that take place is useful for us to fall in love with science and encourage its dissemination. We should not forget, however, that some of these reactions are dangerous, so they should not be repeated at home.