Five cool chemical reactions explained in videos


Oozing snakes and exploding volcanoes, all thanks to chemistry.


Pharaoh's serpent

This reaction is created by burning white powdered mercuric thiocyanate – an inorganic chemical compound.

The tendril byproducts are made of carbon nitride.

Warning: if you fancy taking on this chemical reaction, think again. The materials are highly toxic and the reactions extremely poisonous.

Iodine clock

This reaction, know as the iodine clock, occurs when a solution of hydrogen peroxide is mixed with a combination of potassium iodide, starch and sodium thiosulfate.

After a few seconds the colourless mixture suddenly turns dark blue.

There are a number of variations of this experiment. In some, the solution will repeatedly cycle from colourless to blue and back to colourless, until the reagents are depleted.

Black snake

This reaction involves the dehydration of sugar (sucrose) with sulfuric acid.

The dehydration reaction is a type of elimination reaction. Sugar is a carbohydrate, so when you remove the water from the molecule, you're left with elemental carbon.

Although the sugar is dehydrated, the water isn't "lost" in the reaction. Some of it remains as liquid in the acid. Since the reaction creates heat (exothermic) much of the water is boiled off as steam.

Ammonium dichromate volcano

This reaction involves the decomposition of ammonium dichromate.

As the ammonium dichromate breaks down, it sprays orange sparks and throws the green chromium oxide crystals into the air, producing an effect that looks like a miniature volcanic eruption.

Even though majority of the materials' mass escapes as vapour, the end product appears larger than the materials it started with.

Elephant’s toothpaste

Elephant's toothpaste is a foamy substance caused by the rapid decomposition of hydrogen peroxide.

This is often used for classroom demonstrations because it requires only a small number of ingredients to produce a volcano of foam.

It's sometimes known as the "marshmallow experiment", but is unrelated to the Stanford psychology marshmallow experiment.

Related reading:
A better explanation for why sodium explodes in water

  1. https://cosmosmagazine.com/physical-sciences/better-explanation-why-sodium-explodes-water
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