Author: Huang Ben (Institute of Chemistry, Chinese Academy of Sciences)
Drawing: Flying
Source: Knowledge is Power magazine
Magic is always fascinating with incredible phenomena, and there are many types of magic. Chemical magic mainly uses the strange chemical properties of matter and various interesting phenomena produced in chemical reactions to achieve incredible, fake and real artistic effects, often giving the audience a wonderful experience and shocking visual impact. Below, we will take a few new and interesting chemical magic scenes as examples to reveal the chemical principles behind these magical magic tricks.
Magical tea reduction
The magician brewed a cup of tea, filtered out the tea leaves, and then drank a few sips, which was a cup of fragrant tea. The magician wanted to cast magic on the cup of tea, only to see him stir it a few times with a spoon, and the tea instantly turned into an ink-like blue-black; the magician stirred it with the spoon a few times, and the blue-black in the cup magically disappeared, and the tea returned to its original fresh tea color. What's going on?
●Magic Revealed●
Redox reactions commonly found in chemistry are involved here. The magician coated the lower end of the spoon with alum (feso 4·7H2O ferrous sulfate heptahydrate), because the tea contains tannic acid (tannic acid), the first stirring, tannic acid encounters the ferrous ion Fe2+ in the green alum and immediately generates ferrous tannin acid, the nature of ferrous tannic acid is very unstable, and it is quickly oxidized to form a complex of iron tannins and appears blue-black. The magician also coated the upper end of the spoon with reducing properties of oxalic acid (HOOC-COOH), the second stirring time the spoon was submerged deeper into the teacup, the trivalent iron ion Fe3 + met the oxalic acid, was reduced to the divalent ferrous ion Fe2 + and generated a ferrous oxalate precipitate, the blue-black of the solution disappeared, reappearing the original color of the tea.
An ice maker who fills water into ice
The magician takes out a glass of water and tells the audience to condense it into ice at room temperature. After putting the spoon in the water, the magical phenomenon happened, the spoon produced ice crystals and continued to "grow", and finally the whole cup of water became "ice". Without being frozen, a glass of water really solidifies into a piece of "ice".
The cup is not filled with ordinary water, but a pre-prepared sodium acetate supersaturated solution, sodium acetate is also known as sodium acetate, the molecular formula is CH3COONa, generally in the form of hydrate that combines 3 water molecules, the appearance is colorless transparent or white particles. The sodium acetate supersaturated solution can exist at room temperature, but is in an unstable metastable state, and crystals will precipitate when disturbances occur under external conditions, such as vibration, friction, or the addition of condensation nuclei. When the magician dips some sodium acetate crystals on the spoon into the solution, there is a condensation nucleus, and the sodium acetate in the solution begins to crystallize on the condensation nucleus, and the newly precipitated crystal can be used as a crystal seed, so the crystal continues to extend outwards and grows. Because the crystals of sodium acetate are similar in appearance to ice, the spectacle of "freezing" at room temperature appears.
Dreamlike artificial snowflakes
The magician took out a white paper cup and displayed it in front of everyone. There was nothing unusual about the empty cup that people saw, and the magician said that he could make snowflakes out of the cup, said that he took some water and poured it into the empty paper cup, shook it a few times, and then the magician grabbed a handful of white snowflakes from the paper cup. Without the need for cooling, without the need for a large snow machine, the water turns into a crystal beautiful "snowflake" in an instant, which is really amazing.
Of course, water does not automatically turn into snowflakes, and the mystery of magic lies in the paper cup. It turned out that the magician had previously coated the bottom of the cup with a layer of white powder: sodium polyacrylate, which is a long-chain polymer that crosses with each other into a spatial network structure. When sodium polyacrylate powder encounters water, water molecules enter it through capillary action and diffusion, and sodium polyacrylate is then dissociated into positively charged Na+ and negatively charged polymer ion chains. Due to the electrostatic repulsion between COOs on the polymer ion chain, the structure of sodium polyacrylate stretches (or swells). The osmotic pressure formed by the difference in the concentration of Na+ ions inside and outside sodium polyacrylate makes the water molecules penetrate further and form a hydrogel. Therefore, the volume of sodium polyacrylate will expand several times after absorbing water, so that the original powder becomes a piece of white "snowflake".
A spoon that disappears out of thin air
The magician brought a cup of warm water, only to see him pick up the spoon in his hand and stir it in the cup continuously, but this time the water did not change in color or state. At this time the magician stopped stirring, took the spoon out of the water, and people were surprised to find that the tip of the spoon had disappeared. Did the magician do anything to this cup of water and dissolve the spoon?
The spoon disappears not because of the incredible substance added to the water, but in the spoon itself, although this spoon is also made of metal, it is not our common stainless steel or aluminum alloy, but a strange metal with a very low melting point - gallium (Ga). Gallium is a silvery metal, in the periodic table gallium is in the 31st place, and aluminum is a "relative" of the family. The melting point of gallium is only 29.8 ° C, and the human body temperature can slowly melt the gallium, and the solid gallium made of a spoon in warm water will soon melt into a liquid sinking into the bottom of the cup, giving people the illusion that the spoon disappears out of thin air.
The use of chemical elements as magic props relies on the specificity of the substance itself. Simple chemical elements can construct countless forms of matter to form this colorful world. Chemistry can help magic bring us a strange visual experience, but also to build a real but fantasy world, to provide us with a beautiful material and spiritual life, which may be the biggest magic that chemistry has.
(Editor-in-Charge / Huang Yingying Art Editor / Li Ziye)