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Electrical wonders. Chemical experiments

Entertaining experiments in chemistry

Entertaining experiences at home / Chemistry experiments for children

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  • Battery from aluminum circles
  • Copper battery
  • Battery from an old battery
  • Water is decomposed by electric current into oxygen and hydrogen
  • How to detect electric current
  • How to distinguish between plus and minus batteries
  • How to make copper coating on steel
  • Metal pattern by electroforming
  • Patina - how to get a patina on copper and bronze
  • Table salt is decomposed by electric current on electrodes
  • Drilling holes with electric current
  • Old battery and its secondary charging
  • Old battery and its revival
  • Blackening of copper
  • Electricity cleans dirty water
  • Electrochemical drill - from a medical syringe
Electrical wonders require:

Electrical wonders

By the way, do you know why batteries give current? Because a chemical reaction takes place in them. Batteries are said to be chemical current sources. But if so, can not some unusual transformations take place under the action of the current? They can. The science that studies such transformations is called electrochemistry. With the help of electricity in laboratories and factories, new substances are obtained, metals are dissolved, one metal is deposited on another, and water is purified. In a word, they make tens and hundreds of useful chemical miracles.

Let's do the same.

As I said, we do not need a strong current. But it would not hurt to learn how to detect weak and very weak electric current.

There is such a simple way: lick both battery contacts at the same time. A sour taste immediately appears on the tongue. The more acidic it is, the better the battery is charged. Not acidic at all - the battery is worthless.

But I can't recommend this way. Firstly, there may be dirt on the contacts, and you don’t know what to lick with your tongue - you’re not some stupid thing. Secondly, if the battery is brand new, then the feeling can be quite sharp. Better to do otherwise. And by the way, the result will be clearer.

Pour water into a mayonnaise jar, pour a teaspoon of table salt, stir until it dissolves, and add a few drops of phenolphthalein solution. Close the jar with a plastic lid with two holes (for example, you can pierce them with an awl in advance). Pass copper wires through the holes - so that they are immersed in the solution, but do not touch one another. This is a current detection device. Check it out at work. Attach the wires to the poles of the battery - the current will immediately give itself away: at one of the wires the solution will turn crimson. There, alkali was formed from table salt.

But this device does more than that. It can recognize where the battery is positive and where it is negative. (They are always marked like this: the positive pole - with a "+" sign, the negative - with a "-" sign.) Did you pay attention to which wire the solution was colored? No matter how many times you repeat the experiment, a crimson color appears at the wire connected to the negative pole. That is, with the one where the "minus" is drawn on the battery.

In order not to prepare the solution again each time, you can also do this: moisten a strip of filter paper or blotting paper with it and press the strip with your fingers to both poles of the battery. Near the negative pole, the paper turns red. This is very convenient when you need to know where the "plus" is, where the "minus" is, and the battery wrapper is torn or dirty so that nothing can be disassembled. Having such an indicator of electricity, you can proceed to further experiments. First, using the simplest means, try to make a real chemical current source. Or, to put it simply, a homemade battery.

You will need some "silver" paper: it has one side really paper, and the other metal, usually aluminum; "Silver" it only in appearance. Tea and cigarettes are wrapped in such paper; it is sometimes sold in stores for various homemade products. Cut this paper into circles a little smaller than a nickel. And at the same time stock up on the nickels themselves - ordinary copper coins. You will not spoil them: after the experiment they will be no worse than before.

Moisten the cut "silver" paper properly with a solution of table salt. While it gets wet, polish a dozen copper nickels to a shine. And then collect a stack of paper circles and nickels in the following sequence: first "silver" paper (paper down, "silver" up), then a nickel, then paper again, and so on; the last penny will be on top. Take two flexible wires twenty centimeters long and carefully remove the insulation from the ends with a knife to expose the copper veins. Put one wire under the pile, the other on the pile and tightly wrap it with insulating tape so that the copper veins are well pressed: one to the paper, the other to the top nickel. The battery is ready.

I'm afraid that the bulb from such a battery still does not light up. But if you connect the wires to the indicator jar (or if you attach a strip of blotter moistened with a solution to them), then after a minute or two a red color will appear. And that means the battery is working. Where it has a positive pole, where it is negative, you will figure it out yourself.

If you can cut nickel-sized circles out of aluminum, you can make a more powerful battery. Between the nickels and aluminum mugs, put a blotting paper soaked in a salt solution; below, as before, let there be paper, at the top - a nickel. Wires and electrical tape, of course, are also needed.

A real battery, although it contains completely different substances, works on the same principle. It has positive plates and negative plates, and between them is some solution that can conduct electricity (like a salt solution). Every two plates is an electrical element. And a lot of elements - a battery. Ours consists of ten elements. A flashlight battery usually contains three cells. You can open the old battery: there are three metal cups in it.

If you have already reached the glass, then carefully break it and take out the thick mass from the inside that surrounds the carbon rod. This mass consists mainly of manganese dioxide. In old batteries, it is usually almost dry. Scrape it, dry it, grind it into a powder and add some glue of some kind. Spread this mixture on a piece of "silver" paper on the metal side and let dry, and then cut the paper into rectangles the size of a matchbox. Fold a stack of rectangles so that there is paper at the bottom, metal in the middle, and plaster on top. Attach the wires to the top and bottom of the stack, wrap with electrical tape and put everything together in a matchbox, leaving only the wires outside. This is another battery option. Check her out. It may happen that you overdry the spread, and then the battery will not work. In this case, it either needs to be held briefly over the steam so that it picks up moisture, or you can slightly moisten the paste with a solution of salt or ammonia (ammonium chloride).

Homemade batteries give a small current. But if you make several batteries, check them and connect them with copper wires, then, quite possibly, a small light bulb will light up from such a combined battery and the micromotor from a self-propelled toy will start working. And you need to connect in parallel. That is, positive poles with positive, negative - with negative (I hope you did not forget to mark them with "+" and "-" signs).

Now I will give you advice on how to make an old battery work, which, it would seem, has come to an end. It may happen that the battery of the receiver "sits down" just during an interesting transmission. Or the flashlight will go out at dusk...

Do not rush to throw away the battery. She can be revived. Most batteries - both for flashlight and receiver - contain the manganese dioxide you know in a zinc cup. Almost nothing happens to the glass, and the dioxide is rather quickly covered with a shell of substances that interfere with the electrochemical reaction. If only this shell could be broken...

So let's destroy the harmful shell around the useful substance. The easiest way: tap the battery with a hammer or stone. Not too strong, so as not to break it, but not too weak, so as to still destroy the shell. The battery will come to life, albeit not for long.

There is a way to revive and more reliable. Take a nail and a hammer, punch a hole in a zinc cup with a nail (keep in mind that there is only one cup in round batteries). And then dip the battery into the water. The paste will soak in the water, it will be easier for it to penetrate the grains of manganese dioxide. So you can extend the life of the battery by about a third.

And if you have time, patience and a transformer for the children's railway, then the old battery can be recharged. But only if it is not damaged, and the paste inside is not completely dry. In this case, using the indicator jar, determine where is the "plus" and where is the "minus" of your transformer (this is not dangerous, the voltage is low), connect the "plus" to the "plus" of the battery, "minus" to the "minus" and leave for an hour or two to charge. Keep an eye on the red light on the device. If it lights up, immediately turn off the device: a short circuit has occurred in the battery, it is no longer possible to charge it.

For further experiments, you need obviously good batteries, new or restored on your own. It is more convenient to work with flat batteries (for a flashlight). In the next experiment, you will need two of them, and connected in series - "plus" one to the "minus" of the other.

Take two strips of any metal ten centimeters long. You can cut them, for example, from tin or thin aluminum. On one side, make small holes in the plates and thread the wires through them. If the wires are insulated, then do not forget to peel it off in the place where they come into contact with the metal.

Dip the records in a small jar, say mayonnaise. The distance between them should be small, a few millimeters. So that they do not touch, put a lump of plasticine on top and bottom. Hang the records directly on the wires, and how to fix them - please figure it out yourself.

Pour water into the jar, painted over with any ink, so that the liquid is opaque. Connect the wires to the batteries. After a minute or two, the liquid between the plates will gradually begin to lighten. Dark particles will collect at the bottom in the middle of the jar. And a dirty foam forms at the top.

The composition of the ink contains very small particles of dye. Under the influence of electricity, they unite, stick together. Heavy particles, of course, sink to the bottom. But some of them float to the top along with foam bubbles: they are picked up by a gas that is formed from water under the influence of an electric current.

This is how electricity can purify dirty water. True, this process is very expensive, so it is used in exceptional cases. But what is this gas from water? And what actually happens to water under the influence of current?

We learn all this from experience. In a thick-walled glass, insert a circle cut out of plywood a few centimeters from the bottom with two round slots of just such a width that a simple pencil fits tightly into them. Next to the slots, poke two small holes with an awl, into which thin insulated wires can enter. Insert two halves of well-ground pencils into the slots. At their other end, unfinished, make notches with a knife so that the stylus appears, and wind the bare ends of the wires. Copper veins should fit snugly against the lead. Wrap them with electrical tape, and if you have a rubber tube, then pull it on top so that the insulation is sure to be reliable.

Insert the circle into the glass so that the sharpened ends of the pencils stick up (but not higher than the edge of the glass), put this structure on a plate and pour a solution of washing soda to the brim (two teaspoons per glass of water). Pour the same solution into two test tubes or into tall vials. Take one test tube, close it with your finger, turn it over and lower it into a glass. Under water, put a test tube on a pencil. Do the same with the second tube.

Connect three batteries in series ("plus" of one - to the "minus" of the next), and connect the wires coming from the pencils to the extreme batteries. The device is on. A glass, strictly speaking, is called an electrolytic bath, a soda solution is called an electrolyte, pencils are called electrodes, and what happens in the bath is electrolysis. But what's going on there?

Water contains charged hydrogen particles. They move towards the positive electrode. And near the pencil, which is attached to the "plus" of the battery, bubbles of hydrogen rise up. And the second pencil has bubbles of another gas - oxygen.

When a full test tube of hydrogen is collected (it will displace almost all the water), carefully remove it from the solution and, without turning it over, bring a match: hydrogen will flare up and pop like a firecracker. And cover the test tube with oxygen under water with your finger, remove it, turn it over and lower the extinguished, but still smoldering splinter into it: in the presence of oxygen it will ignite again.

It turns out that water under the action of electricity decomposes into hydrogen and oxygen. This property is often used to produce hydrogen gas (and there is enough oxygen in the air).

But why put soda? Just to speed up the experience. Water is a very poor conductor of electricity, and without soda, our experience would have been too long.

With the same device, repeat the experiment again, taking table salt instead of soda. In one test tube, as before, hydrogen will appear, and in the other - yellow-green chlorine gas. Do you remember what table salt is called in chemical language? Sodium chloride.

Actually, chlorine is quite poisonous, but you get it in very small and safe amounts. Close the test tube with chlorine and salt solution residues with your finger, take it out of the water, turn it over and shake it several times. In the test tube - chlorine water, a very strong oxidizing agent. To verify this, add this water to a weak ink solution - it will immediately discolor.

Near the negative electrode, drop a little phenolphthalein solution. He will blush. So, it also turned out to be alkali. Really alkali, and strong and often used - caustic soda. It turns out that under the action of a current, a solution of ordinary salt immediately gives three useful substances - hydrogen, chlorine and caustic soda. Table salt, which we all appreciate as an essential seasoning for food, is also highly valued in industry: it is a very important raw material.

Now we will set up another experiment with a solution of common salt. True, for the industry it does not matter, but it looks much more beautiful than the previous one. Actually, he is not much different from him. Only instead of slate electrodes, from a simple pencil, take copper electrodes this time. They can be thin copper plates, or even easier, cut two rectangles of copper foil.

Put red copper rectangles vertically along the edges of a small plastic bath or enameled tray. Pour a solution of table salt into the bath (the ratio of water and salt does not really matter); let this solution cover the rectangles a little more than half. Then, with two wires, connect the copper electrodes to the positive and negative poles of the flashlight battery. The experience has begun.

Watch what's going on in your electrolytic bath. First, as in the previous experiment, small bubbles of gas appear near both plates. True, this time chlorine is not formed - hydrogen is released at both electrodes. And the alkali at the negative electrode can be detected even now. But the most interesting is ahead.

After about five or ten minutes, green flakes will appear in the liquid. It was from sodium chloride that green copper chloride was formed (but not immediately, but through a whole chain of transformations). However, this is not all.

Leave the device on and come back to it in about an hour. You will see that the solution has turned yellow, and a yellow precipitate has appeared at the bottom. The alkali that appeared at the electrode reacted with one of the copper compounds and formed a very thin precipitate, which gradually changes color from yellow to red. Such a color change occurs even faster when heated, but in this case it is not necessary, because our electrolyte heats up a little on its own, under the influence of an electric current. Eventually, the red precipitate mixes with the yellow, forming a brownish mass at the bottom of the bath.

It may happen that this experience will not go to the end, and the transformations will be interrupted somewhere in the middle. Most likely, the reason is that the battery "sat down" during operation. I'm afraid that revival will not return her to her former strength, which is simply necessary for this experience. So replace the old battery with a fresh one.

And one more observation that I advise you to make. Examine carefully both electrodes after the experiment. They will be covered with a bloom: one is black, the other is greenish. We will learn how to prepare such colored films on copper on purpose, but we will do it a little later.

In the next experiment with electricity, we will dissolve the metal. But since such an activity in itself is not very meaningful, let's do this: we will dissolve the metal in a certain place so that a through hole is obtained in a piece of metal. In other words, we will drill metal using electric current.

Prepare a saturated solution of table salt and pour it into a saucer. Connect the positive pole of the battery with a wire to some thin metal plate, such as a razor blade. Make sure that the wire fits snugly against the metal. Take a pencil with a notch and wire from the salt experiment, connect the wire to the negative pole of the battery. Break off the sharpened pencil lead and dig it a little deeper with a needle to form a notch half a millimeter deep. Put the blade in a saucer with a solution of salt and touch the metal with a pencil.

As soon as the broken lead approaches the razor, hydrogen bubbles will appear. And the blade will begin to dissolve. And after ten minutes, a through hole forms in it. If, instead of a razor, you put aluminum foil in a saucer and take a new battery, then the hole will appear in a matter of seconds.

The experience can be somewhat modified - do not put the razor or foil in a saucer with a solution, but leave them in a dry place. But then you have to dip the pencil in salt, and you will have to drip water on the place where the hole will be. From time to time it is necessary to wipe the metal with a clean cloth and apply a new drop of water. Tin from a tin can is drilled in this way quickly enough. And thicker metal requires more current. Well, in this case, take not one, but two or even three batteries connected in parallel ("plus" to "plus"). And do not forget to clean the hole, and then drip fresh water and dip the pencil in salt.

And one more electrochemical drill: from a medical syringe with a needle. Draw a saline solution into the syringe. Put an inverted glass in a plate, put a razor or some kind of plate attached to the "plus" of the battery on its bottom, and attach a second wire to the "minus" of the battery. Wrap its other stripped end around the syringe needle. Slowly press down on the piston, and a thin stream of solution with the help of current will quickly drill through the metal.

Now let's cover one metal with a layer of another metal. For example, white iron with red copper.

Wait a minute, you've already dipped a nail into a solution of blue vitriol, and it turned red with copper. So why current?

Then, without it, the layer of copper on the iron turns out to be loose, fragile: if you run a rag over it, it peels off. And we need the metal to stay on the metal for a long time. Copper plating and other similar operations in a factory are usually carried out in baths into which a suitable solution is poured and the part is lowered under current. But this is not always possible. What if you need to cover the ship's plating with metal? In such cases, special devices are invented. Like the one you're doing now.

Take apart a damaged fountain pen (not a ballpoint pen, but the one that writes with ink) and push out the device in which the pen is held with a nail. In an ink bottle, draw a strong solution of copper sulphate. Remove the insulation from the soft stranded wire, insert the bundle of wires tightly where the pen was once. The device for drawing with copper is ready. Let's take care of what to draw on.

Any metal plate, preferably steel, should be polished to a shine with sandpaper, washed and put in a solution of washing soda, which should boil for several minutes so that no dirt remains on the surface of the plate. Then rinse it again with clean water and connect the plate with wires to the negative pole of the battery. Connect the bundle of wires protruding from the pen to the positive pole - and get to work.

Slowly drive the "pen" over the plate, and it will be covered with a layer of copper before your eyes. Keep an eye on the wires soaked in liquid. When the liquid is running out, collect a new portion of the copper sulphate solution; however, for simplicity, you can dip the pen into the solution from time to time. But in any case, make sure that the wires do not touch the plate: there should always be a layer of liquid between them.

If you cover a nail or a knitting needle with red metal, then it will take a little time and one battery will be enough. It takes more time to play a record, and one battery may not be enough. Well, take two batteries connected in series ("plus" to "minus"); the third will be useless. When the copper layer has been applied, dry the plate and rub it well with a soft woolen cloth. Copper will shine, as polished copper can shine.

But copper shines for the time being. Old copper and bronze objects (and bronze contains copper) become covered with a green coating. Sometimes they try to get rid of it, and sometimes, on the contrary, they protect it. For example, on ancient statues.

If you want, you can make a touch of antiquity not in a year or a month, but in an hour or two.

And also with the help of electricity.

Take a piece of copper foil or a copper plate from a previous experiment. Attach the wiring (if you are dealing with foil, then pierce a hole in it for the wiring), put it in a soda solution and boil. Rinse with water and dip in a weak solution of vinegar so that the clean copper surface does not oxidize in the air. In a glass of water, stir two teaspoons of ammonia (ammonium chloride) until dissolved. Remove the vinegar plate by the conductor and rinse under running water, being careful not to touch the copper with your hands. Dip in a solution of ammonia and connect the conductor to the positive pole of the battery. Connect any other copper object, not necessarily as pure, to the negative pole. Soon the plate will be covered with a matte red layer. After five minutes, remove it by the wires and, without touching it with your hands, hang it over the table. Substitute a plate or tray below so that the remnants of the solution do not drip onto the table. An hour later, the red layer will turn emerald green. This green coating is called patina. Or even a noble patina.

When a patina develops slowly, over decades and centuries, it lasts for a long time. We got her in an hour, and her life is calculated in hours. To keep the patina longer, cover it with some colorless varnish (for example, nitro varnish). I can’t vouch for a century, but I promise a year of life ...

Not only patina gives metal products a noble shade of antiquity. Silver that has blackened over time also looks very beautiful, and art connoisseurs will never allow silver jewelry to be polished to a shine: let black remain on it. Moreover, niello is specially applied to some products, especially chased ones, so that the details appear more distinct and embossed.

Of course, no one will allow us to experiment with precious silver, and we ourselves will not do it: you never know what can happen to jewelry! And you can blacken copper, brass, and bronze objects. If you yourself or someone you know is fond of chasing, you can cover the chased jewelry with niello. However, any copper or brass plate is suitable for the experiment.

The composition of the blackening solution is very simple: dissolve 5 g of sodium hyposulfite (from a photoshop) in about a tablespoon of water and add a little more than half a tablespoon of regular 9% vinegar. Do not be surprised to find a yellow cloudy suspension in this solution. This is as it should be, because under the action of vinegar from hyposulfite, the sulfur contained in it is released.

Take a saucepan large enough so that your copper or brass plate rests on it, resting on the edges. Pour water into a saucepan, boil it and put a plate in place of the lid, thoroughly washed with washing powder. Now the steam rising from the boiling water will heat the plate all the time, and it will turn black pretty soon if you smear it with the yellowish mixture prepared earlier. Choose the time of the experiment yourself: the longer it is, the thicker the color is. It may happen that the color is brown rather than black. This means that you need to slightly increase the amount of hyposulfite and vinegar in the initial mixture (or reduce the amount of water).

The explanation for this reaction is very simple: copper reacts with sulfur to form a black substance called copper sulfide. When this compound is obtained, it is necessary to remove the blackened plate from the saucepan and cool it, and then wipe it with a clean cloth with some kind of dish cleaner or at least with tooth powder. This is a very useful operation, because it allows you to remove excess blackness and brighten the raised areas, which makes the drawing clear and voluminous.

After such clarification, it is useful to polish the object with a soft cloth with some kind of polishing liquid, but this is already at your discretion. If you just wanted to get acquainted with blackening, then you can not polish. If you decide to make a beautiful thing even more elegant, then you hardly need to spare time to bring it, as they say, to full brilliance.

In the next experiment, using electrochemistry, we will make some little thing directly from the solution. This is called electroforming. It is very useful in cases where the part has a very complex shape and cannot be made in any other way. Let's say, a copy from a gramophone record - how exactly to convey the shape of the grooves, imperceptible even to the eye?

You and I, perhaps, cannot copy a gramophone record. And to make some kind of pattern or monogram, that is, your initials, is please.

Take a piece of wax or paraffin from a candle, smooth the surface properly; you may have to slightly warm it in warm water. On a smooth area, scratch a shallow pattern with a thin needle: a pattern, letters - whatever you want. Remove the lead from a simple pencil and crush it as finely as possible. With a soft brush, apply slate powder to the drawing. To the surface covered with graphite, press two thin copper wires along the edges and connect them together. Hang this cast in a glass or jar. It will be more convenient to put a pencil or stick on the edge of the vessel and hang the cast on them - on a thread or on wires connected together. And on either side of it, hang any two copper plates, at least pieces of copper foil. Connect the wires from them to the "plus" of the battery, the wires from the graphite-coated cast to the "minus".

Pour a solution of copper sulphate into the vessel (a tablespoon in a glass of water) and do something else while the court is on the case. Copper will be deposited for five hours, or even more. It could be sooner, but then its layer will be fragile. Therefore, be patient. You won't need more than one battery, and if it's not very new, it doesn't matter either ...

After a few hours, disconnect the wires from the battery and carefully remove the wax or paraffin cast. Gently lower it into hot water. The malleable material will melt, and you will have a thin copper pattern in your hands. Tear him off the wire and the experiment is over.

Author: Olgin O.M.

 We recommend interesting experiments in physics:

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nomad
The way to charge a dead battery is to put it in a cooking (dry) one and wait from 2 to 4 hours and the battery can be used!

Danil
Super!

a guest
Soda conducts electricity?


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