In order not to get confused, let's take something accessible and well-studied for experiments. For example, sugar. Moreover, while doing summer miracles, you have already set up some experiments with him. The sugar in the sugar bowl has the chemical name of sucrose. His closest relatives, sweet and not very sweet, are called like this: sugar. Or so: carbohydrates. It is the same.

Sucrose you can lick, gnaw, put in tea and porridge. That is what it is intended for. And all other substances that will be obtained in the experiments, without special permission, do not try. Otherwise, sweet miracles will turn into bitter disappointment.

The unusual phenomenon that you will now see with your own eyes is very difficult from a scientific point of view. And it is done simply. And do not need any substances other than sugar. Stock up on two or three pieces of refined sugar and a tablespoon of sand, preferably large, in the form of crystals. That's all for now.

No, not everything, you still need a dark room. Let's say a bathroom, closet, closet. Warn them not to open the door for a few minutes and turn on the light. Sit in the dark to get used to it, so that your vision becomes sharper. And then - for experiences. There are only two of them.

The first experience - with refined sugar. Hold a lump of sugar firmly in your hand and strike it with force several times on some not very smooth surface. Let's say cement. Or on rough tiles, which are used for floors in bathrooms and stairwells. If you pick up the right material and get the hang of striking a piece of sugar on it, then the eye, accustomed to the dark, will notice how luminous streaks will stretch behind the sugar. In fact, they disappear almost immediately.

Maybe you have a coffee grinder with a transparent lid at home. In this case, try to grind a piece of refined sugar in it (again, of course, in the dark). And this time the sugar will glow distinctly. But why?

When you press sugar crystals against a hard surface, tiny electrical sparks ignite due to the intense friction. This is the shortest way to explain this miracle. The second miracle has the same explanation; for him you will need a mortar and pestle, it would be nice to have porcelain.

As before, stay for a few minutes in a dark room. Pour some granulated sugar into the mortar in advance. Accustomed to the dark, slowly rub the sand in a circular motion. Then move the pestle faster, faster, faster. And now, in the mortar, a ring of tiny sparks glows with a cold blue light.

When you practice, when you get the experience flawlessly, you can invite spectators into the darkness with you. Remember that if you do the experiment with a mortar slowly, without speeding up your movements, then instead of a ring, separate sparks will appear - and this also makes an impression.

Now let's move on to the transformation of sugar. In a tablespoon, preferably an old one, put granulated sugar and hold it over the fire. A sticky, brown, pleasant-smelling mass is formed, called burnt sugar, or caramel. Perhaps you saw how your mother or grandmother prepared it for culinary needs; creme brulee ice cream gets its color and smell also thanks to burnt sugar. Of course, you can taste it - if the spoon was clean.

And what happens if you heat a lump of sugar directly on the fire? Let's check. Hold a piece of sugar with tweezers or tongs and bring it into the flame of a candle or match. Sugar doesn't ignite. And when you hold it longer, the familiar smell of caramel and a brownish color appear.

Let's change the experience a little. Pour some cigarette ashes directly on a sugar lump (and this, as far as I know, is the only case when smoking is of any use - not for health, of course, but for chemical experiment). So, pouring ashes and bringing a lump of sugar to the flame, you will see that this time it lights up! True, sugar does not burn very brightly and melts during combustion, but it still burns. What happened to him?

While doing summer miracles, you tested inhibitors contained in plants. That is, substances that slow down chemical reactions. And maybe I thought then: what if there are substances with the opposite effect - such that they do not slow down, but, on the contrary, accelerate reactions?

Such substances do exist. They are called catalysts. In the entire vast chemical industry, there are not many reactions that do without catalysts. When the reaction does not go fast enough, a catalyst is selected for it - and the matter is accelerated by tens and hundreds of times.

Substances contained in tobacco ash served as a catalyst for the combustion of sugar. And in the next experiment, the catalyst will be acid. With it, you will turn one sugar into two. More precisely, you will turn sucrose (the one in the sugar bowl) into glucose and fructose. Glucose is also called grape sugar, and fructose is also called fruit sugar.

In factories preparing delicious things for us, say syrups and jams, they often make such a transformation. You know that homemade jam becomes candied when it has been left unused for a long time. Sugar crystals stand out from the liquid, just like in experiments on crystallization. They crunch on the teeth, and in general, the jam is not at all what it used to be ...

With the jam that is sold in the store, such a misfortune happens much less often. A mixture of glucose and fructose, that is, grape and fruit sugar, almost does not crystallize during storage. It is obtained by heating from ordinary sugar, using a catalyst. In industry - sulfuric acid. But she is caustic, it is better not to deal with her. We will completely manage with citric acid, much weaker, but safe, even if it is eaten a little.

Dissolve four to five tablespoons of granulated sugar in half a glass of hot water. The glass must be with thin walls (otherwise it may burst). It is even safer to take an enamel mug. Throw a pinch of citric acid directly into the hot solution or, if there is a desire and opportunity, squeeze the juice from a quarter of a lemon. This juice, of course, also contains citric acid.

Put a glass or a mug with a solution in a saucepan of boiling water, that is, in a water bath, and hold it there for half an hour. Outwardly, nothing seems to have changed, but in fact, serious transformations have taken place with sugar. And now you will be convinced of it.

Pour some solution into a vial and add a few drops of methylene blue dye solution to it. This dye is used as a medicine and sold in a pharmacy; but you can also take blue for linen diluted in water, blue ink for fountain pens. Pour a little ammonia or a solution of washing soda into the vial, put it in hot water and observe the color. Very soon, the contents of the vial will become almost colorless. Do exactly the same experiment with an ordinary sugar solution - the color will not even think of changing. It means that some changes have really taken place with sugar. Each of its molecules broke up into two, smaller ones: into molecules of glucose and fructose. Both of these substances are sweet and edible, but their chemical properties are not quite the same as those of sucrose.

Such a mixture is usually called invert sugar. Let's give him another chemical test.

Pour a little alkali into a test tube - ammonia or a boiled solution of washing soda. Add a few drops of copper sulfate solution. A blue precipitate of a substance called copper hydroxide will immediately appear. Carefully drain the liquid, and add a few drops of the invert sugar solution prepared by you with a pipette to the hydroxide precipitate. Shake the test tube several times, of course, closing it. The precipitate will dissolve, forming a dark blue solution.

But that is not all. Heat a test tube with a dark blue solution in a boiling water bath. At first the solution will turn yellow, then it will turn orange, and eventually a red precipitate will fall to the bottom. Both of these reactions definitely indicate that glucose is present in our sweet solution. To finally verify this, buy glucose tablets in a pharmacy, dissolve one or two tablets in water and do both reactions with copper sulphate and alkali. They will go exactly the same.

Glucose is found not only in grapes (although it was called grape sugar), but in many vegetables and fruits. Repeat the same experiment with apple, pear, carrot or cucumber juice. Rub a little apple, pear, etc. on a grater, squeeze the juice and strain it through cheesecloth, and then do with it exactly the same as with a solution of invert sugar. By the way, it's time for us to return to him. While you were taking samples and studying bright reactions, the contents of a glass or mug must have cooled down completely. Heat the mixture of glucose and fructose in a water bath, but this time heat longer so that the water from the glass evaporates. The solution will gradually thicken and turn yellow. Pretty soon it will start to resemble honey...

Nothing surprising. One stripped off solution of invert sugar with the addition of honey or honey essence is artificial honey. It is sold in stores and is usually used for cooking, because it is much cheaper than the real one. The fact is that bee honey also consists of three-quarters of glucose and fructose. Cool the thick liquid you have obtained, add a little natural honey to it, stir and taste: not bad at all.

The experiment can be repeated by taking orange juice instead of citric acid. Or any other sour juice. Or even non-acidic, but with the addition of citric acid. You will get very different, but invariably appetizing syrups that you can safely eat, since you took edible and tasty products for them.

If the artificial honey doesn’t seem thick enough to you, take a stronger sugar solution and keep it in a water bath longer so that more water evaporates. But do not try to heat for speed right on the fire; you get not honey, but brown caramel.

Have you noticed that the prepared syrup, even if it is very thick, does not crystallize, but remains liquid? In fact of the matter. Jam on invert sugar is really almost not candied. So you can safely advise the elders when they decide to make jam: if the berries or fruits are not sour in nature, then it does not hurt to add citric acid before the end of cooking. Your advice is doubly valuable, because you give it not by hearsay, but on the basis of experience set by your own hands ...

They say not all that glitters is gold. And we will add: not everything is sugar that is sweet. Take glycerin for example. It tastes distinctly sweet, and even its name means "sweet" in ancient Greek. But according to the chemical structure, glycerin belongs to the so-called polyhydric alcohols, and not to sugars ...

Let's do a beautiful reaction that will allow us to distinguish glycerin from the real sugar - glucose, without tasting these substances.

Boil the washing soda solution and pour it into two test tubes (or two vials). Add an approximately equal amount of glycerin to one test tube, and the same amount of glucose solution to the other. Then drip alternately into both vials a few drops of a blue solution of copper sulphate. A blue precipitate will form in both test tubes, which will dissolve easily after shaking, forming a saturated dark blue solution.

For a person who has already studied chemistry, there is nothing surprising here: glucose, like glycerol, contains alcohol groups, which means that some reactions in these substances should go the same way. But in general, these substances are not very similar, and the difference can be detected in the next experiment.

Heat the dark blue liquid in two vials in a water bath. Watch how the color changes. A solution containing glycerin will not react to heating in any way - as it was blue, it remained blue. But the liquid with glucose will behave differently: a yellow precipitate will fall out of it when heated, which will turn red upon further heating. This reaction is typical for many sugars, but not for glycerol.

Is it possible to turn glycerin into real sugar? I mean sugar in the chemical sense of the word, not the sugar in the sugar bowl. In the chemical sense, you can transform. But it is still not necessary to taste the product that will result from the reaction. We recognize it not by taste, but by a color reaction.

The very solution that did not want to change its blue color when heated, cool to room temperature and add a little, no more than two drops, pharmacy hydrogen peroxide. Stir the mixture and again put it in a water bath, that is, in a saucepan with hot water. And now it will behave almost the same as a glucose solution: first it will turn yellow, then it will turn yellow-red, and, in the end, a red precipitate will fall out. Glycerin, as you remember, is not typical at all, but only real sugars. Such a transformation occurred with glycerol under the action of a strong oxidizing agent - hydrogen peroxide.

Grape sugar (glucose) can be distinguished from cane or beet sugar (sucrose) by another chemical reaction, long known, simple and beautiful. It is called the silver mirror reaction. The word "silver" is used here not figuratively, but in the most direct sense: during this reaction, a thin and shiny layer of silver appears on the glass.

At the pharmacy, buy a pack of glucose, a bottle of ammonia and silver nitrate. From your experiments with photography and Liesegang's rings, you must remember this substance, better known, however, under the name "lapis". As before, a lapis pencil is quite suitable for our experiment, despite the fact that it contains some impurities.

The essence of the silver mirror reaction is that glucose, unlike sucrose, is capable of reducing metallic silver from its compounds. And this silver, if the experiment is set correctly, settles in the form of a thin layer on the glass wall of the vessel.

A very important warning: the vessel must be perfectly clean. I advise you to conduct this reaction in a test tube or in a transparent vial, previously washed, as they say, to a full shine, and not from the outside, but from the inside. For example, like this. First, armed with a brush, wash a bottle of soda or washing powder. Then put it in a saucepan with the same soda (or powder), put on fire and boil. Finally, rinse several times with running water.

Pour about 20 ml, that is, a tablespoon, of ordinary water into a very clean vessel. Add a crushed glucose tablet - it usually weighs half a gram. Shake the water so that the tablet is completely dissolved, set the vessel aside and take care of the second solution.

Dissolve the tip of the lapis pencil in a small amount of water and add ammonia drop by drop. There will be sediment first. Continue to drip ammonia, and the precipitate will gradually dissolve. As soon as it completely disappears, stop adding ammonia and dilute the resulting solution with water by about half.

Now return to the vessel with the glucose solution. Pour the second solution into it to fill the vessel almost to the top, stir, heat in a water bath, in boiling water. Now you hardly need to be reminded that in no case should you hold it with your bare hands. Take a clothespin or a homemade wire holder. Better yet, make a holder so that you can put it on the edge of the saucepan and free your hands.

Be that as it may, if the vial is washed properly, then very soon a brilliant silver mirror will form on its walls. Maybe it won't be as pretty as you'd like. Then repeat the experiment, taking a new, equally clean vessel, and try to change the ratio of the first and second solutions. Usually you have to take less lapis solution or, what is the same, more glucose solution.

Sucrose does not give a silver mirror reaction. If you want to believe, you want to check. But I highly recommend trying a solution of invert sugar. The experience is set in the same way as with glucose, but take two to three times more home-made invert sugar. And also see how some clear juice behaves from among those that, according to your observations, contain glucose. It is possible that this time you will not get a beautiful mirror, but you will notice the reaction at least by the dark particles of silver that are collected in flakes.

Finally, let's take a look at the starch. Please don't be surprised. Starch, although unsweetened, is also from the sugar family. Its huge complex molecule consists of many molecules of glucose and other simple sugars connected to each other. Under the right conditions, starch breaks down into its constituent parts and becomes sweet!

But how can we detect that the starch molecule, as it breaks down, gets smaller and smaller? With the help of iodine. Remember, diluted iodine tincture turns starch blue? This means that the less starch remains, the weaker the color will be. And when all its molecules break down into its component parts, it will completely disappear.

Pour two teaspoons of starch into a saucepan or into a clean tin can, pour a glass of cold water, stir and heat, stirring all the time, until you get a transparent sticky solution - starch paste. An acid catalyst must be added to it. And here comes the difficulty. With citric acid, starch molecules will break down very slowly. Vinegar is not good because it volatilizes when heated. For the same reason, it is also inconvenient to work with hydrochloric acid: you will have, firstly, to add it to the saucepan from time to time, and secondly, to ventilate the room well.

In factories, they do this: they add a little dilute sulfuric acid. But I think it's too early for you to work with such a corrosive substance on your own. Therefore, please ask your elders to cook you just a little bit, literally one or two teaspoons, of diluted acid. It is sold in hardware stores, but for the sake of a spoon you should not buy a whole bottle. A few drops of acid can be borrowed from any motorist: car batteries are poured with sulfuric acid. When one of the elders will dilute acid with water for you - about ten times - then please remind him that you must definitely pour acid into water, and not vice versa, otherwise you can burn yourself. Even a few drops.

When sulfuric acid is so strongly diluted, it is no longer very hot, but it can eat through clothes to the hole. Therefore, carefully pour the acid solution into a saucepan or a jar of paste: there it is so diluted that it is no longer dangerous at all. Put the mixture on low heat and let it boil slowly. If the liquid boils noticeably, add water to the previous level.

Shortly after the start of cooking, take two or three drops of hot liquid with a pipette, drop it on a clean glass, let it cool a little, and with another pipette, drop a diluted iodine tincture. As you remember, a blue color should appear. From time to time take a new sample of the mixture and test it with iodine. The blue color will soon change to red-brown. So things are going well. These are formed "fragments" of starch molecules, they are called dextrins. And then there is a substance similar to sucrose - maltose, aka malt sugar. Maltose, in turn, turns into glucose, which iodine does not stain at all. As the starch breaks down into simpler and simpler substances with the help of an acid catalyst, the color with iodine will change. It is possible that it will not completely disappear, because the finished product is not pure glucose or maltose, but a mixture of many substances that were formed during the reaction. In this form, it is called molasses and is often used in confectionery factories.

But as long as there is acid in the molasses, it, of course, cannot be taken into the mouth. When the color from iodine disappears completely or becomes very weak, boil the mixture for another five to ten minutes, remove from heat, cool slightly and gradually add a tablespoon of crushed chalk or tooth powder while stirring: with it you will get rid of acid. It reacts with chalk, while carbon dioxide is rapidly released, which is very convenient - while the mixture boils and foam appears, you know that the acid is still left. And as soon as the bubbles and foam have disappeared, the acid is over. Still heat the liquid on fire so that excess water boils away, and strain through cheesecloth folded in several layers. You got molasses, which, unfortunately, is not as tasty as we would like: it is bitter due to the addition of chalk. At factories, molasses is cleaned much better, but this is not available to us. So you can try it, but there is - I do not advise ...

In our body, in the stomach, starch also decomposes to maltose and further to glucose. And without any acid (not to mention sulfuric). And catalysts are special natural substances that are in any living organism. They are called enzymes.

How one of the enzymes works, you will now see with your own eyes. Its name is "amylase", it is found in saliva and is able to convert starch into maltose. Which is very important for us, especially when we eat potatoes or bread, which have a lot of starch.

Rinse your mouth with clean boiled water for about a minute. Put a sheet of blotting paper or gauze folded into three or four layers into the funnel, lightly moisten it with water, insert the funnel into a glass and pour water out of your mouth into it. You will get a clear solution of saliva. Mix it with an equal amount of cooled starch paste, pour the mixture into a vial and put it in a glass of warm (about 40 ° C) water. As before, take samples from time to time with iodine on a glass slide. The color will change in the same sequence as in the reaction involving sulfuric acid. But pay attention: this time it goes without any boiling and much faster. After fifteen minutes, the mixture will stop staining with iodine.

Catalysts created by nature act quickly and accurately. No wonder chemists try to adapt these substances so that they can work not only in living organisms, but also in factory apparatus.

And here is the last of the sweet wonders. It does not require any test tubes, no iodine, no lapis. Nothing but a piece of white bread.

Put some bread in your mouth and chew it carefully for a few minutes. You will feel how it tastes more and more sweet. And you won’t be surprised at this anymore, because you know: this is how the amylase enzyme works, turning completely unsweetened starch into sweet sugar maltose.

Author: Olgin O.M.

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