burned at a constant rate of three inches per hour. By measuring the length of the remaining part, it was possible to determine quite accurately how much time had passed since such a watch was put into operation.

Double helix... There was something surprisingly familiar about this image. But what? Well, of course, the DNA molecule has the shape of a double helix. True, the spiral of ropes burns out in a few hours, but the DNA helix continues to copy itself throughout the life of the cell...

Eret began to look for a unique organism, by experimenting with which he could confirm his guess. The choice fell on the ciliate slipper - a simple single-celled organism. “Usually ciliates are more active during the day than at night,” Ehret reasoned. “If we manage to disrupt the rhythm of its life by influencing a DNA molecule, we can consider it proven that this molecule also serves as a biological clock mechanism.”

He chose a light beam as an instrument of influence. After a series of experiments, he was able to find out that by exposing the shoe alternately to ultraviolet radiation and white light, it was possible to either greatly change the rhythm of life of the ciliate, or restore it again.

“Ultraviolet damage damages the DNA helix, but the cell can repair the damage if, after an ultraviolet pulse, it is exposed to white light,” Ehret concluded.

A little later, Ehret's findings were confirmed by other scientists who influenced the DNA molecule with various chemicals.

ria, the essence of which boils down to this.

The DNA molecule, which in this case the American scientist called “chronon,” is coiled in a tight spiral in the cell nucleus. When duplication of the molecule begins, the strands of such a helix diverge, and messenger RNA is built on them, reaching the full length of a single strand of DNA “chroion”. At the same time, a number of interconnected chemical reactions take place, the ratio of speeds of which can be considered as the work of the regulating mechanism of a clock.

Ehret viewed his model as “a skeleton in which all the details are omitted...”. But in these details, apparently, the basis of the biological clock is hidden. What chemical reactions occur when DNA is duplicated?..

"RAINBOW" IN A TEST TUBE

Two decades ago, Soviet scientist B.P. Belousov discovered a new type of pulsating redox reactions. The liquid in the test tube changed its color right before our eyes: one moment it was red, now it was already blue, then it turned red again... The color change occurred strictly periodically.

Belousov spoke about the phenomenon he observed at one of the symposiums. The message was listened to with great interest, but no one, including the author himself, attached much importance to the fact that the initial components of pulsating reactions are organic substances, very similar in composition to the substances of a living cell, to DNA substances. Only in 1960 did another Soviet scientist pay attention to this and develop a detailed recipe for such reactions.

"Open Days"
in the chemistry room

Every year in April the school hosts an “Open Day” held by high school students. Elementary school students and preparatory kindergarten students come to the chemistry classroom, and high school students tell them about the science of chemistry and demonstrate entertaining experiments.

Such meetings are of great importance for both spectators and demonstrators. It is no secret that currently in Russia, and throughout the world, there is chemophobia, which causes an initial disdain for the subject. But after such meetings this problem ceases to exist for us. And the kids can’t wait to start studying this fascinating science.

High school students acting as teachers, along with experimental skills, develop pedagogical and often artistic abilities, because simultaneously with the demonstration of experiments, the children act out mini-performances.

It must be remembered that for kindergarten students, meetings should be no more than 10 minutes. During the demonstration, children need to be explained that all the experiments are jokes (the snake is not real, we are doing a make-believe operation, etc.), and they must be warned not to try to repeat anything themselves at home. For elementary school students, the meeting may last 25–30 minutes.

Scenario for "Open Day"
for kindergarten students

Teacher. Hello, dear guys! Today you have come to the most amazing office of our school. After all, those who study chemistry become a little wizards. After lessons, the guys grow crystals (student assistant demonstrates the best specimens of crystals), make candles that burn with multi-colored flames (demonstrates) make paints and paint with them Besides this, the guys can do a lot more and will show you their favorite experiments.

1st student. Today I will show you a real rainbow. I will add this magical substance to seven identical test tubes. And you tell me the color that comes out.(The student adds a universal indicator to solutions of acid, aluminum chloride, distilled water, tap water, solutions of sodium dihydrogen phosphate, sodium hydrogen phosphate, sodium hydroxide.)

And now I will add a colorless solution to these test tubes with a raspberry solution. What do you see?(Add potassium sulfite to acidified, neutral and alkaline solutions of potassium permanganate.)

Teacher. And I will show you an experiment that we called “Chemical Dragon”. I add the most important sulfuric acid for chemists to the white powder in a glass vessel.(The sugar in the cylinder is charred and rises up the cylinder, the process is accompanied by the release of water vapor.)

2nd student. Guys, do you like to sit by the fountain in the summer? We love it too, but it’s a pity that it’s not summer now, and there’s no fountain nearby. Although, if you know chemistry, then nothing is impossible.(A flask filled with ammonia and closed with a stopper with a long pipette inserted into it is brought to a crystallizer filled with water with the addition of phenolphthalein. The flask is turned over, lowering the pipette into the crystallizer. Water rises through the pipette, fills the flask, the color of phenolphthalein changes.)

3rd student. And now you will see several magical transformations in one test tube.(Alternately, solutions of iron(III) chloride, sodium carbonate, hydrochloric acid, potassium thiocyanate, sodium fluoride, sodium hydroxide, sodium sulfide are added to a large test tube. First, a brick-red precipitate forms, then it dissolves, a clear solution is formed, which, when added, thiocyanate potassium turns blood red. After adding sodium fluoride, the color disappears. When adding alkali, a brick-red precipitate forms, and at the end a black precipitate forms.)

1st student. Just think, I can do even better. ? % hydrogen peroxide solution, sodium sulfide. First, a turquoise precipitate forms in the blue solution; when acid is added, the precipitate dissolves and gas is released. After adding potassium iodide, a precipitate appears, changing its color from yellow to brown. After adding sodium thiosulfate, the precipitate turns white, then a bright blue solution is formed, which "boils" when hydrogen peroxide is added.

2nd student. And at the end a black precipitate appears again.) Guys, do you like to take pictures? Now I'll take a photo of you. Look at this piece of paper carefully. The most attentive person on it will succeed. The photograph must be developed.(Sprays the sheet from a spray bottle.)

3rd student. Who did we get?(A face is drawn on the sheet with an alkali solution, and a phenolphthalein solution is in the spray bottle.) Which one of you is the bravest? Oh, so many! Well then, come over, I’ll cut you. What, there are no takers?(If none of the children decides, the “operation” is performed on one of the demonstrators.) Assistant, give me iodine.(The student gives a solution of iron(III) chloride.) To make everything sterile, we will apply iodine generously(dips cotton wool into the solution and wets his hand). Scalpel! Every operation requires sterilization(dips the scalpel into a solution of potassium thiocyanate, brings it to his hand and gently holds it). You see, what a great guy!.

1st student. The blood flows, and he smiles. Now we'll cure(wipes his hand with cotton wool soaked in a solution of sodium thiosulfate).

2nd student. You see, there is no trace of the cut And now we will arrange a real festive fireworks display in honor of your arrival.

3rd student. (Students add a solution of hydrochloric or sulfuric acid to test tubes with chalk and close them with stoppers. There should be several stoppers for each test tube. When one flies out, close the test tube with the next stopper, etc. It is better to take plastic stoppers.)

Finally, we will show you our favorite Volcano Eruption experience.
(Lights ammonium dichromate poured onto a metal sheet.)

Our meeting is over. But we say goodbye to you for a short while. While you are in primary school, you will be regular guests in our office. And when you grow up, you will probably show the experiments to the kids yourself.

1. "Open Day" for primary school students

2. Entertaining experiments"Magic Vessel" . At the beginning of the event, a little ammonia solution is poured into the bottom of the desiccator and flowers are placed there, which gradually change their color.

3. "Unusual metal" The pre-moistened scarf is moistened in ethyl alcohol. One student holds the scarf with tweezers, the second sets it on fire.

4. "Fireworks". Sodium and sulfur are ground in a mortar, the mixture ignites and burns with a spray of sparks.

5. "Smoke without fire." One cylinder is moistened with concentrated hydrochloric acid, the second with ammonia, both are covered with glass.

6. The cylinders are brought close to each other and the glass is removed. Thick white smoke fills the vessels.

7. "Mysterious Letters". A pattern is applied to the sheet with a pre-saturated solution of potassium nitrate and dried. The lines must not intersect or be interrupted. Set fire to the beginning of the outline of the drawing. The fire spreads along the line and the design appears.

8. "Firebird". Crystals of copper, lithium, strontium, calcium, and sodium chlorides are placed in a porcelain cup with ethyl alcohol.

9. Alcohol is set on fire: salts color the flame in different colors. The experience looks better when darkened."Old Man Hottabych"

10. . 0.3 g of aluminum powder and 4 g of iodine are placed in a porcelain cup. The contents are ground, a drop of water is added with a pestle, which acts as a catalyst for the reaction.

11. Brown-purple smoke is produced. The experiment should be carried out in a fume hood."Fire Without Matches"

12. . 0.3 g of potassium permanganate is placed on a steel sheet, moistened with concentrated sulfuric acid, and sawdust is piled around it. Ethyl alcohol is dripped from above. Spontaneous combustion occurs."Golden Rain"

13. . First, a yellow precipitate of lead iodide is obtained from lead acetate and potassium iodide in a test tube. Add acetic acid to the precipitate and heat until the precipitate disappears. When demonstrating an experiment, a test tube with a solution is lowered into a glass of cold water. Beautiful scaly crystals fall out."Chemical algae".

Iron, copper, nickel, cobalt, chromium and other colored salts are added to the silicate glue solution in advance.

"Marmalade."

Phenolphthalein and hydrochloric acid are added to the silicate glue solution.

A solid silicic acid gel, similar to jelly or marmalade, forms in the test tube; the test tube is turned over, the contents are not poured out.

"Sand Snakes". A small mound of sand is poured onto a steel sheet, a dry fuel tablet is placed inside, and a norsulfazole tablet is placed on top. Set fire to dry fuel. A huge black “snake” crawls out of the sand.

Professional competition for educators

Place of work: Municipal autonomous educational institution"Experimental Lyceum "Scientific and Educational Complex"

Ust-Ilimsk

Extra-curricular event of multi-age cooperation between middle and primary levels. At this event, 9th grade students act as cooks and consultants for 4th grade students in the form of a theatrical performance. This event is held with the aim of introducing children of 4th grade graduates to a subject teacher who will teach a lesson at the secondary level, that is, the teacher conducts a short-term internship in the class where he will work.

Target :

To introduce 4th grade students to the science of chemistry, to develop their interest in this subject so that they study it with passion and desire. Develop continuity of knowledge and skills between primary school and secondary school.

Tasks:

1. broadening the horizons of students;

2. creating conditions in which junior students would begin to think actively, while receiving intellectual pleasure;

3. development of communication skills and the ability to work in groups;

4. show that science is a living, exciting business;

Equipment:

For “drinks” 4 beakers

Experience No. 1 – seven large test tubes, a demonstration rack with a white background;

Experience No. 2 – a beaker with a capacity of 500 ml, a porcelain cup with cold water, an alcohol lamp, matches, a tripod with a ring, an asbestos mesh, a spruce sprig;

Experience No. 3 – alcohol lamp, matches, steel loop;

Experience No. 4 – tile, matches, splinter;

For riddles: flask, funnel, beaker, scales, the rest in experiments No. 1-4.

Reagents:

For “drinks”: solutions of sodium hydroxide, sodium carbonate, barium chloride, hydrochloric acid, phenolphthalein;

Experience No. 1 – chemical rainbow (color of precipitation in an exchange reaction) solutions:

1. Ferric chloride and potassium thiocyanate
2. Potassium chromate and sulfuric acid
3. Lead Nitrate and Potassium Iodide
4. Nickel sulfate and sodium hydroxide
5. Copper sulfate (II) and sodium hydroxide
6. Copper (II) sulfate and ammonia solution
7. Cobalt chloride and potassium thiocyanate;

Experience No. 2 – Winter miracle (sublimation and crystallization of benzoic acid):

Benzoic acid, solid;

Experience No. 3 – Fireworks (flame coloring with metal salts):

Solid lithium salts are red, sodium is yellow, calcium is brick red, copper is green and a mixture of these salts is a multi-colored flame;

Experience No. 4 – Vulcan (decomposition of ammonium dichromate):

Ammonium dichromate (solid), alcohol;

Work in groups of 4 people(definition of starch):

Petri dish, iodine solution, pieces of bread and apple, rice, pasta.

Children from 9th grade act as cooks.

Decor:

1. "Chemical Cafe" sign
2. badges for students - cooks 2 pieces
3. menu for tables according to the number of groups
4. 2 white coats for chef students

Description of experiments

Beverages:

1. “fruit drink” - add phenolphthalein to a glass with an alkali solution, a crimson color appears;
2. “milk” - pour the solutions of sodium carbonate and barium chloride into a glass, these are colorless liquids, a white precipitate forms;
3. “carbonated drink” - add a solution of hydrochloric acid to the resulting “milk”, carbon dioxide is released.

Experiment No. 1 – Chemical rainbow (color of sediments in an exchange reaction)

We pour the solutions in pairs into seven large test tubes placed in a demonstration rack with a white background, obtaining colored precipitates in the colors of the rainbow:

1- iron (III) chloride and potassium thiocyanate (red);

2- acidify the potassium chromate solution with H 2 SO 4 (Orange color);

3- lead nitrate and potassium iodide (yellow);

4- nickel(II) sulfate and sodium hydroxide (green);

5- copper (II) sulfate and sodium hydroxide (blue);

6- copper (II) sulfate and ammonia solution (blue);

7- cobalt (II) chloride and potassium thiocyanate (purple color).

1. FeCl 3 + 3KCNS = Fe(CNS)3 + 3KCl

2. 2K 2 CrO 4 + H 2 SO 4 = K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O

3. Pb(NO 3 ) 2 + 2KJ = PbJ 2 + 2KNO 3

4. NiSO 4 + 2NaOH = Ni(OH) 2 + Na 2 SO 4

5. CuSO 4 + 2NaOH = Cu(OH) 2 + 2Na 2 SO 4

Experiment No. 2 – Winter miracle (sublimation and crystallization of benzoic acid):

Place 5g of benzoic acid and a spruce sprig into a beaker with a capacity of 500 ml. We close the glass with a porcelain cup with cold water and heat it through an asbestos mesh on an alcohol lamp. The acid sublimes and crystallizes when cooled, filling the glass with “frost” that covers the twig.

Experiment No. 3 – Fireworks (flame coloring with metal salts):

We introduce salt crystals on a steel loop into the colorless flame of an alcohol lamp, after calcining it in the flame until the color disappears.

Experiment No. 4 - Vulcan (decomposition of ammonium dichromate):

Pour ammonium dichromate onto a heat-resistant surface (tile), use a splinter to make a depression (volcano crater) and pour a little alcohol into it. Light the alcohol with a splinter. Ammonium dichromate decomposes with the release of nitrogen and water vapor, swelling the mixture with the resulting chromium (III) oxide.

(NH 4 ) 2 Cr 2 O 7 → t Cr 2 O 3 + N 2 + 4H 2 O

Externally, the reaction resembles an active volcano. After its completion, chromium (III) oxide occupies a volume approximately 3 times larger than the original substance. It should be noted that particles of the resulting chromium (III) oxide - “volcanic dust” - will settle around the volcano, so the experiment must be carried out on a large tray.

Scenario

Teacher:

Hello guys, guests. Welcome to our office. You are here for the first time today, my name is Marina Nikolaevna, next year I will teach a subject called natural history or, in other words, natural study.

Do you know what sciences study nature? (correct, geography, biology, chemistry)

Think about how and with what help you can study nature? (yes, this is an observation, experience or experiment, research).

Today we invite you to use them in our “Chemical Cafe”.

You are in an unusual cafe: you can prepare many interesting dishes and drinks that do not exist in others.

What are the magic chefs Vladimir and Pavel cooking here? Check out the menu of our cafe, it is on your tables.

Chef 1:

Hello guys. We are glad to see you in our “chemical cafe”. To prepare these dishes, we will conduct various chemical experiments.

Chef 2:

This is a wonderful activity - chemical experiments! You take one substance, react with another and get a third! I know that you guys haven’t studied chemistry yet. What is chemistry?

Chef 1:

This is the science of substances and their transformations.

Chef 2:

And what is it?

Chef 1:

This is what everything in the world consists of.

For example: a desk, and the substance is wood

Chemistry deals with a wide variety of substances: liquid and solid, colorless and bright, strong and fragile, useful and harmful.

Chef 2:

What is transformation?

Chef 1:

This is when one substance turns into another, or like this: there were two substances, but they became one.

Chef 2:

Want to see how it happens?

Look at the menu: what are you interested in?

Teacher:

We are interested in how to prepare the drinks that are on the menu?

Chef 1:

It's very simple: we mix two colorless liquids (lye and phenolphthalein), what do you notice?

(color change) what color is the liquid? (raspberry color). What drink does it look like? (for fruit drink)

Chef 2:

We will now prepare a drink more suitable for you. Mix the two colorless liquids again

(sodium carbonate and barium chloride). What changes are happening now? What drink does this look like?

(white color – milk). This drink is very healthy, especially for children.

Chef 1:

In the summer, when it’s hot, how do you quench your thirst? (soda) In the next experiment we will get it.

Add a colorless liquid to the “milk” and what happens? (violent release of carbon dioxide).

You see, we got water, and sparkling water too!

Chef 2:

Now, guys, choose any dish from the menu that you would like to see: a volcano, a chemical rainbow, fireworks, a winter miracle.

(demonstration of experiments of any sequence)

Teacher:

These are the magical chefs who work in our chemical cafe! And although you can’t eat here, their dishes are the most interesting and unusual.

Did you guys like them?

What did you learn from us today?

Is chemistry science or witchcraft? What does chemistry study? What is a substance? What are transformations?

Chemistry is a very interesting science with which you can create miracles

I invite you to work with substances today too. Since we are in a cafe, we need to know which food products contain the substance starch.

Chef 1:

Starch is a carbohydrate that a person needs to obtain energy and it is found in the kitchen in its pure form (show the packaging and the substance from it).

Chef 2:

How can we detect it in products, for example, we have bread, apples, rice, pasta?

Chef 1:

Yes, it’s very simple: you need to drop a solution of iodine, and if the product turns blue, this means that it contains starch.

(all students work in groups of 4, each researching one product)

Teacher:

What did you learn in our chemistry cafe? (to determine the starch content in food products), and how was it discovered? (well done, the iodine solution helped us)

Chemistry is an interesting science with which you can create miracles!

You can’t conduct experiments without chemical glassware. Want to know what it's called?

To make the experience beautiful,
The giant will help us:
Made of glass, for reagents,
Myselfbeaker.

I have a hole at the top
To pour and pour.
I -glass test tube,
A chemist should know this.

I porcelain cup,
Unfortunately, they don’t drink from me.
They don't cook porridge for food.
They are experimenting in me.

The chemist knows one thing:
What is a round bottom flask?
There is also an unyielding one -
Flask only flat-bottomed.

Light my wick,
And whatever you want, heat it up.
The alcohol in me burns deftly,

And my name is alcohol lamp.

From a glass, a ringing stream:
We will pour the liquid.
If you pour through funnel ,
It will be possible to filter.

I am a spatula, I observe strictly.

So that you don’t take a lot of substances.

It's enough to scoop up a handful,

Then rinse with water.

Many chemists know:

The whole will be the reagent

In their test tube. After all, like legs,

The test tube has a STAND

Behind the lined glass

Write the volume in numbers.

They only pour liquid into me

And they call it BEASERS.

Two twin cups

Accurate as scales

Always in harness

Their name is SCALES.

So our meeting ended. As in any cafe, you, visitors, can leave your reviews about our establishment.

(younger schoolchildren leave reviews on small pieces of paper).

Bibliographic description: Matveeva E.V., Mardanova R.Z., Matveeva L.I. Chemical rainbow // Young scientist. 2018. No. 3. P. 87-91..05.2019).



Relevance

We are surrounded by compounds and substances of various colors, including the most interesting phenomenon in nature is a rainbow appearing in the sky. Why do substances have different colors, and some compounds change color like chameleons? Is it possible to obtain a chameleon material that can change color? This is relevant in light of the development of new developments in the field of nanotechnology.

Target: Explore the properties of inorganic chameleon substances.

Tasks:

1. Familiarize yourself with compounds that have a specific color.
2. Find out the areas of application of compounds of different colors.
3. Determine what factors determine the color of various compounds.
4. Select the appropriate reagents and carry out sequential chemical reactions with the color of the solution in one flask changing to the colors of the rainbow.
5. Try to get a chameleon material.

Working hypothesis. It is possible, using reagents containing compounds of chromium, vanadium, manganese and copper, as a result of chemical reactions to carry out a sequence of transformations during which the color of the solution in the test tube will change in the order of the colors of the rainbow.

Novelty In a practical way, a sequence of chemical reactions was carried out in one flask in the order of the colors of the rainbow. An attempt to obtain a chameleon material.

Object of study. Compounds of d-elements: manganese, chromium and vanadium.

Deadlines andplace of research. The research was carried out in the laboratory of MOAU "Lyceum No. 1" in Neftekamsk in 2017–18.

Research methods: search and research, observation, comparison, experiment.

Practical part

Experiment 1. Colored rainbow intest tubes, , , , .

To obtain the colors of the rainbow in different test tubes, pour the following solutions into 7 test tubes in pairs:

In the 1st test tube iron (III) chloride and potassium thiocyanate (red):

FeCl 3 + 3KCNS = Fe(CNS) 3 + 3KCl

To the 2nd test tube: acidify the potassium chromate solution with H 2 SO 4 (orange color):

2K 2 CrO 4 + H 2 SO 4 = K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O

In the 3rd test tube: lead nitrate and potassium iodide (yellow)

Pb(NO3) 2 + 2KI = PbI 2 + 2KNO 3

In the 4th test tube: Nickel(II) sulfate and sodium hydroxide (green);

NiSO 4 + 2NaOH = Ni(OH) 2 + Na 2 SO 4

In the 5th test tube: copper (II) sulfate and sodium hydroxide (blue);

CuSO 4 + 2NaOH = Cu(OH) 2 + 2Na 2 SO 4

In the 6th test tube: copper (II) sulfate and ammonia solution (blue);

CuSO 4 + 4NH 3 = SO 4

In the 6th test tube: cobalt(II) chloride and potassium thiocyanate (purple color)

CoCl 2 + 2KCNS = Co(CNS) 2 + 2KCl

Experiment 2. Rainbow in the 1st flask., , , , , , , .

In one flask, reactions were carried out that resulted in a change in the color of the solution in a sequence of rainbow colors.

1) Getting red color. A small amount of chromium (VI) oxide crystals and water were added to the chemical flask: CrO 3 + H 2 O = H 2 CrO 4

As a result of the reaction, red chromic acid H 2 CrO 4 was obtained.

2) Getting orange color. Then CrO 3 crystals were additionally added to the same flask: H 2 CrO 4 + CrO 3 = H 2 Cr 2 O 7 orange dichromic acid

3) Getting yellow color. An excess of an alkaline NaOH solution was added to the resulting dichromic acid:

H 2 Cr 2 O 7 + 4NaOH (ex.) = 2Na 2 CrO 4 + 3H 2 O gave yellow sodium chromate.

4) Getting green. Hydrosulfide acid was then added to the flask. As a result of the reaction, a green precipitate of Cr(OH) 3 is obtained, due to which the solution turns green. 2Na 2 CrO 4 + 3H 2 S + 2H 2 O = 2Cr(OH) 3 ↓ + 3S + 4NaOH

5) Getting blue. If we add copper sulfate to our flask, then sodium hydroxide, which is present in the solution, will react with it

2NaOH + CuSO 4 = Cu(OH) 2 ↓ + Na 2 SO 4

The reaction should result in a blue precipitate of Cu(OH) 2, but since green Cr(OH) 3 is present in the solution, the solution acquires a blue color.

CuSO 4 (g) + 4NH 4 OH = SO 4 + 4H 2 O

The result is a blue solution of copper (II) tetraamine sulfate SO 4.

7) Getting purple. To obtain a purple solution, we need to add potassium permanganate to our solution, which will react with excess copper sulfate. CuSO 4 + 2KMnO 4 = Cu(MnO 4) 2 + K 2 SO 4

We obtained a solution of copper permanganate Cu(MnO 4) 2, which has a purple color - the final color of our rainbow.

Experiment 3."Step-by-step recovery of VO3 ─ to V2+ zinc metal inacidic environment", , ,

Placed 0.25 g in a flask. ammonium vanadate NH4VO3 and added 20% hydrochloric acid solution. A transparent yellow solution was obtained. When 6–7 zinc granules are added to the resulting solution, atomic H2 is released, which gradually reduces vanadium V to valence II through intermediate stages. The solution gradually changes color to blue, green, and purple.

First, ammonium metavanadate is reduced to vanadyl chloride VOCl 2

blue: 2 NH4VO3 + Zn + 8HCl = 2VOCl2 + ZnCl2 + 2NH4Cl + 4H2O

Then vanadyl chloride is reduced to green vanadium chloride (III) VCl 3:

2VOCl2 + Zn + 4HCl = 2VCl3 + ZnCl2 + 2H2O

And finally, vanadium (III) chloride is reduced to vanadium (II) chloride, purple: 2VCl3 + Zn = 2VCl2 + ZnCl2

The reduction reactions of vanadium V +5 proceed stepwise with the formation of intermediate ions with a characteristic color: +5 (yellow), +4 (blue), +3 (green), +2 (violet).

Experiment 4."Chemical Chameleon"(dependence on pH of the environment) , , , .

A raspberry solution of potassium permanganate was poured into three beakers. They poured a little diluted hydrochloric acid into the first cylinder, water into the second, and sodium hydroxide solution into the third. Then sodium sulfite was added to all glasses and mixed well with a glass rod. In the first cylinder, the solution instantly becomes discolored, in the second, along with the discoloration, a brown flocculent precipitate falls out, and in the third, the crimson color changes to bright green. You can also put a raspberry solution of potassium permanganate next to them for comparison.

These experiments show how potassium permanganate behaves in various environments.

So in an acidic environment it is reduced to the Mn2+ ion (colorless solution):

2КМnО4 + 5Na2SO3 + 6HCl = 2MnСl 2 + 3H2O + 5Na2SO4 + 2KСl

In a neutral environment, reduction proceeds to manganese (IV) oxide (brown precipitate):

2KMnO4 + 3 Na 2SO3 + H2O = 2MnO2↓ + 2KOH + 3 Na 2SO4

In a highly alkaline environment, MnO42- ions are formed (green color)

2КМnО4 + Na 2SO3 + 2NaОН = 2 Na2MnO4 + K 2SO4 + H2O

Experiment 5.An attempt to obtain a chameleon material

Because each surface's chemical composition is unique, it absorbs different wavelengths of light. Changing the surface color requires changes in the chemical composition. But if you try to introduce atoms and ions of chromium, which can take on almost all colors, into the nanostructure of carbon (graphene), you may be able to obtain a chameleon material that will change its color. Then such material could be used as an “invisibility cloak.”

Of course, special equipment is needed to obtain such material. But we tried to obtain such a material from activated carbon, chromium compounds and silicone.

1 option . We obtained a material based on carbon and chromium compounds. To do this, they crushed coal in a mortar, then mixed it with chromium compounds, spread it in as thin a layer as possible on a refractory surface and heated it. The result was a heterogeneous, dark-colored mixture.

Option 2. We made a material based on silicone and chromium compounds. To do this, silicone was melted and ground in a mortar with a mixture of chromium compounds. After cooling, the material separates quite well from the mortar. The resulting material is still quite thick. Under a microscope, individual crystals of multi-colored chromium compounds are visible. In the light, the material reflects light well, but the colors of the various colors are not yet very visible. Here's what we got:

Of course, these are still only hypotheses and trial experiments; further study of the process is required and quite labor-intensive and painstaking work remains to be done to obtain the material.

8) Research results

1. The properties of compounds with rainbow colors and chameleon substances , , , , , , , have been studied.
2. We became familiar with the areas of application of chromium, manganese and vanadium compounds. Chemical compounds of various colors are used in painting, analytical chemistry to determine the qualitative and quantitative composition of substances, textile, glass, paint and varnish industries, etc. , , , , .
3. We found that the color of various compounds depends on:

1) from the interaction of light with molecules of matter;

2) in organic substances, color arises as a result of the excitation of the electrons of the element and their transition to other levels; the state of the electron system of the entire large molecule is important.;

3) in inorganic substances, color is due to electronic transitions and charge transfer from an atom of one element to an atom of another; the outer electron shell of the element plays an important role;

4) the color of the compound is affected by the external environment;

5) the number of electrons in the compound plays an important role.

1. We selected the appropriate reagents and carried out sequential chemical reactions with a change in the color of the solution in one flask in the order of the colors of the rainbow.
2. We tried to obtain a chameleon material based on silicone with chromium and carbon compounds with silicon compounds.

Conclusion

The properties of chameleon substances were studied.

Substances capable of forming compounds of different colors of the rainbow as a result of chemical reactions include d-elements: chromium, vanadium.

Manganese, chromium and vanadium are “chemical chameleons”, capable of changing color when transitioning to different oxidation states.

Research prospects. Further study of the properties of compounds of the elements chromium, copper and manganese.

In the future, it is possible to create such a chameleon material based on chromium and carbon (or silicone) using the latest developments in the field of nanotechnology, which could change color at the request of a person, possibly regulated through nerve impulses. Then it might even be possible to create a material like an “invisibility cloak,” or at least a material that could serve as camouflage.

Practical significance. Using the acquired knowledge in chemistry lessons when studying the topics “ORR”, “d-elements”, etc., demonstrating experiments in lessons and extracurricular activities; application in analytical chemistry when carrying out qualitative and quantitative analysis of substances; [during the restoration of paintings.

Literature:

1. Analytical chemistry. Qualitative analysis. G. M. Zharkova, E. E. Petukhova, St. Petersburg “Chemistry”, 1993. (pp. 235–236).
2. Artemenko A. I. “Organic chemistry and man” (theoretical foundations, in-depth course). Moscow, “Enlightenment”, 2000.
3. Kiplik D.I. Painting technique - M.: SVAROG and K, 1998.
4. Methodical development “Vanadium. Niobium. Tantalum". / Comp. Yu. E. Elliev, Yu. B. Zverev, S. G. Chesnokova. - N. Novgorod
5. Inorganic chemistry, L. G. Baletskaya, Rostov-on-Don, Phoenix, 2010 (pp. 272–288).
6. Workshop on qualitative chemical semi-microanalysis. M. V. Mikhaleva, B. V. Martynenko, M.: Bustard, 2007. (pp. 72–75).
7. Fadeev G. N. “Chemistry and Color” (book for extracurricular reading). Moscow, “Enlightenment”, 1977
8. “Chameleon” material that changes color NanoNewsNet.ru› news/2015/material-khameleon-…
9. Science and life. Interesting about chemistry. From the books of V.V. Ryumin https://www.nkj.ru/archive.
10. How many colors are there in a rainbow? What colors are in the rainbow http://fb.ru/article.
11. Usova Nadezhda Terentyevna. Municipal educational institution gymnasium No. 24 in Tomsk. Usova Nadezhda Terentyevna. Chemical chameleons. Methodological development Tomsk 2006. Usova2.pdf
12. Chemical experiments with chromium and its compounds kristallikov.net
13. Chemistry for the curious | Colored deposits with chromium alhimik.ru
14. Chemistry in reaction equations. Zh. A. Kochkarov, Rostov-on-Don, “Phoenix”, 2017, (pp. 182–211, 226–229,213–223).
15. Chromium and its compounds https://www.tutoronline.ru/blog/hrom-i-ego-soedinenij.

A mixture of substances that, when burned, produces a bright and sparkling white or colored fire, was invented by the ancient pyrotechnicians of Bengal, a part of India located along the Bay of Bengal. This is where the name "sparkler" comes from. Bengal lights, or sparklers, from India spread throughout the world.

Store-bought sparklers consist of wire coated with a flammable mixture and usually produce a white flame. To prepare colored homemade sparklers, first mix starch with water and brew a thick paste.

Then grind the mixture in a mortar iron sawdust, aluminum or magnesium powder, flame-coloring salt and wet "Berthollet salt" - potassium chlorate KClO3 ( Carefully! Dry potassium chlorate, when ground, can ignite metal powders!)

The mixture obtained by grinding is added to the starch paste and mixed thoroughly. The thick mass is transferred into a test tube or a tall glass, pre-prepared iron wires about 1 mm thick are alternately dipped into it to a depth of 8-10 cm, taken out and allowed to drain off the excess mass, and then hung on a rope by a hook bent at the other end of the wire.

After drying, the wires are again dipped into the liquid mass and dried again. These operations are repeated 3-5 times until the layer of mass on the wire reaches 5-6 mm in diameter, after which the sparklers are dried completely.

Green sparkler is obtained by mixing without grinding 5 g wet barium nitrate Ba (NO 3 ) 2 with 1 g aluminum or magnesium powder, then add 3 g iron sawdust Another recipe for green sparkler includes 3.5 g boric acid B(OH) 3 , 6.5 g wet potassium chlorate, 2 g iron filings and 1 g aluminum powder.

Red sparkler yields 4.5 g mixture wet strontium nitrate Sr(NO3)2, 5.5 g potassium chlorate I, 3 years old iron sawdust and 1 g aluminum or magnesium powder.

Yellow sparkler will delight your eyes if you prepare it from 3 g sodium oxalate Na 2 C 2 O 4.5 g wet potassium chlorate, 3 g iron sawdust and 1 g aluminum or magnesium powder.

Colored fire when burning Bengal mixtures is obtained due to the presence of substances containing cations barium, strontium, sodium or atoms boron, capable of emitting light of a certain wavelength in the visible region of the spectrum when entering a flame. Iron Fe, aluminum Al and magnesium Mg in the form of powders or fine sawdust, when burned, produces spectacular sparks. In this case, iron(III) oxide Fe 2 O 3 and partly Fe 3 O 4, as well as Al 2 O 3 and MgO are formed.

The main reaction here is the redox interaction of KClO 3 with starch, which can be conventionally denoted by the formula C 6 H 10 O 5:

4KClO 3 + C 6 H 10 O 5 = 4 KCl+ 6CO 2 + 5H 2 O

Barium nitrate, which causes a green flame to appear, decomposes in the presence of reducing agents (iron, starch) to barium oxide, nitrogen dioxide And oxygen:

2Ba(NO 3 ) 2 = BaO+ 4NO 2 + O 2

Decomposes in a similar way strontium nitrate, giving the flame a red color.

Sodium oxalate when the mixture burns it turns into sodium carbonate And monoxide carbon:

Na 2 C 2 O 4 = Na 2 CO 3 + CO

A boric acid B(OH) 3, releasing water, goes into boron oxide:

2B(OH)3 = B2O3 + 3H2O

More information on oxalates

Oxalates - salts oxalic acid H2C2O4 . 2H 2 O, a colorless crystalline substance. Alkali metal and ammonium oxalates are colorless crystalline substances, highly soluble in water; the remaining oxalates are slightly soluble.

Strong acids in their concentrated aqueous solutions decompose oxalates into salts of these acids, releasing monoxide And carbon dioxide. For example, sodium oxalate Na 2 C 2 O 4 under the influence of concentrated sulfuric acid turns into sodium sulfate, releasing CO and CO 2:

Na 2 C 2 O 4 + H 2 SO 4 = Na 2 SO 4 + CO + CO 2 + H 2 O

Oxalic acid is dibasic and forms two series of salts: medium ones, for example, potassium oxalate monohydrate K 2 C 2 O 4 . H 2 O, and acidic hydroxalates, for example, potassium hydroxalate monohydrate KHC 2 O 4 . H 2 O. When heated, almost all oxalates decompose into metal carbonates And monoxide carbon CO. So, calcium oxalate CaC 2 O 4 turns into calcium carbonate And monoxide carbon:

CaC 2 O 4 = CaCO 3 + CO

With stronger heating, CaCO 3 releases carbon dioxide CO 2, turning into calcium oxide CaO:

CaCO 3 = CaO + CO 2

Oxalates in aqueous solutions exhibit reducing properties. For example, interaction sodium oxalate in an acidic environment with potassium permanganate leads to release carbon dioxide:

5Na 2 C 2 O 4 + 2KMnO 4 + 8H 2 SO 4 = K 2 SO 4 + 2MnSO 4 + 10CO 2 + 5Na 2 SO 4 + 8H 2 O

"Bengal paper"

When ignited, Bengal paper burns with a colored flame, producing no smoke and practically no odor. To prepare it, strips of filter, toilet or napkin paper are soaked in an aqueous solution of salts, which release oxygen necessary for combustion and color the flame, according to the following recipes:

· 2 ml solution ethyl alcohol, 2 g barium chlorate and 2 g potassium chlorate in 10 ml of water (the paper will burn with a green flame);

· 2 ml solution ethyl alcohol, 2 g strontium nitrate and 1 g potassium chlorate in 10 ml of water (flame color is red);

· 2 ml solution ethyl alcohol, 2 g copper nitrate and 1 g potassium chlorate in 10 ml of water (the flame will be blue).

· 2 ml solution ethyl alcohol, 1 g sodium oxalate and 1 g potassium chlorate in 10 ml of water (the flame will be yellow).

Strips of unglued paper soaked in solutions are air dried and then set on fire. The spectacle is unforgettable!

Buran in a glass

Pour 5 g of benzoic acid into a 500 ml beaker and place a pine sprig. Cover the glass with a porcelain cup filled with cold water and heat it over an alcohol lamp. The acid first melts, then turns into steam (evaporates), and the glass is filled with “snow”, which covers the twig with white flakes.

Burning snow

Pour snow into an iron tin can and compact it slightly. Then we make a depression in it (about ¼ of the height of the jar), place a small piece of calcium carbide there and fill it with snow on top. We bring a lit match to the snow - a flame appears, “the snow is burning.”

Calcium carbide slowly reacts with snow to form acetylene, which burns when ignited.

CaC 2 + 2H 2 O ® Ca(OH) 2 + C 2 H 2.

2C 2 H 2 + 5O 2 ® 4CO 2 + 2H 2 O + Q.

Thunderstorm in a glass

“Thunder” and “lightning” in a glass of water!

First, weigh 5–6 g of potassium bromate KBrO3 and 5–6 g of barium chloride dihydrate BaCl2 2H2O and dissolve these colorless crystalline substances when heated in 100 g of distilled water, and then mix the resulting solutions. When the mixture is cooled, a precipitate of barium bromate B, which is slightly soluble in the cold, will form. A(BrO3)2:

2KBrO3 + BaCl2 = B A(BrO3)2Ї + 2КCl.

Filter the colorless precipitate of crystals B A(BrO3)2 and rinse it 2-3 times with small (5-10 ml) portions of cold water. Then air dry the washed sediment. After this, 2 g of the resulting B A Dissolve (BrO3)2 in 50 ml of boiling water and filter the still hot solution.

Set the glass with the filtrate to cool to 40–45 °C. This is best done in a water bath heated to the same temperature. Check the temperature of the bath with a thermometer, and if it drops, reheat the water using an electric stove.

Close the windows with curtains or turn off the lights so that the room is twilight, and you will see how in the glass, simultaneously with the appearance of crystals, blue sparks - “lightning” - will appear in one place or another and clapping sounds of “thunder” will be heard. Here you have a “thunderstorm” in a glass!

The light effect is caused by the release of energy during crystallization, and the pops are caused by the appearance of crystals.

Mining "gold"

Lead acetate is dissolved in one flask with hot water, and potassium iodide is dissolved in the other. Both solutions are poured into a large flask, the mixture is allowed to cool and display beautiful golden flakes floating in the solution.

Pb (CH3COO) 2 + 2KI = PbI2 + 2CH3COOK

Mineral "chameleon". 3 ml of a saturated solution of potassium permanganate and 1 ml of a 10% solution of potassium hydroxide are poured into a test tube. While shaking, add 10-15 drops of sodium sulfite solution to the resulting mixture until a dark green color appears. When stirred, the color of the solution turns blue, then purple and finally crimson.

The appearance of a dark green color is explained by the formation of potassium manganate K2MnO4:

2KMnO4 + 2KOH + Na2SO3 = 2K2MnO4 + Na2SO4 + H2 O.

The change in the dark green color of the solution is explained by the decomposition of potassium manganate under the influence of atmospheric oxygen:

4K2MnO4 + O2 + 2H2O = 4KMnO4 + 4KON.

Smoke without fire

Smoke screens as a result of the combustion of substances without flame or fire, spectacular clouds of smoke on the concert stage or when filming an entertaining historical film or action movie - all this is the work of chemists.Usually, to create such effects, easily sublimated substances are used, which form tiny solid particles of smoke or fog in the air.
This behavior is typical, for example, of paraffin, ammonium chloride, and naphthalene.

One of the “smoking” compositions is prepared by mixing 5 g ammonia(ammonium chloride), 2 g mothballs, 2 g bertholet salt(potassium chlorate) and 1 g charcoal. Such a mixture can only be ignited in the open air, since combustion produces thick smoke without flame, with an unpleasant odor of ammonia and naphthalene.

If you want to show smoke indoors, you need to moisten the inside of the glass with a few drops of hydrochloric acid and, turning it upside down, cover it with cotton wool moistened ammonia. The entire internal space of the glass will immediately be filled with white smoke from the resulting ammonium chloride. To amaze the audience with an unprecedented impression, you can create smoke from water. To do this, pour water into a glass and throw in a piece of “dry ice” - hard ice. carbon dioxide. The water will immediately begin to bubble, and thick white smoke, formed by cooled water vapor, will pour out of the glass. This smoke is completely safe.

Flameless combustion can be achieved using catalysts (chemical reaction accelerators), e.g. chromium oxide(III)Cr 2 O 3 . This is a green powder that is included in many cheap paints as a pigment. Burning without a flame is shown this way: a metal cup is placed on a ceramic tile, into which a little is dripped from a burning candle. paraffin, stearin or wax and immediately, before it cools down, pour Cr powder on it in a heap 2 O 3 . It is necessary that the melted paraffin saturates the powder only from below, and the top layer of chromium oxide remains dry. Now, if you touch the top of the slide with a lit match, a lot of smoke will begin to be released, but no one will see the flame. The combustion reaction of paraffin releases a lot of heat, so it gradually melts and, under the action of capillary forces, rises to the top of the hill, evaporates and forms smoke consisting of particles of solid paraffin.

Chromium oxide will also help show the mysterious disappearance of the substance without flame or smoke. To do this, pile up several tablets of “solid alcohol” (dry fuel), and pour a pinch of preheated Cr on top 2 O 3 . After a while, the entire slide will turn into a pinch of green powder. Oxidation methenamine- solid alcohol base in the presence of a catalyst proceeds in accordance with a reaction where all combustion products are gaseous. A strip of paper soaked in solution lead acetate and dried in air, also burns without flame; it just smolders. In this case, lead acetate is converted into lead oxide and stands out carbon dioxide.

Finally, smokeless and flameless combustion of a substance can be demonstrated by pouring 10-15 ml into a glass acetone(Carefully! Acetone is flammable!) and lower the hot copper wire there so that it does not touch the surface of the liquid. The copper wire will glow until all the acetone is used up. To make the experience even more spectacular, the lights in the room are dimmed. On the surface of copper (which serves as a catalyst and accelerates the reaction), oxidation of acetone vapor occurs to acetic acid And acetaldehyde with the release of a large amount of heat.

Mirror flask

Mirrors appeared long before our era. At first they were metal plates made of gold, silver, copper, polished to a shine, as well as bronze - an alloy of copper and tin. According to the chronicles, with the help of bronze mirrors, Archimedes in 212 BC. “burned ladies' ships in the battle of Syracuse. The production of modern mirrors (on glass) was started in 1858 by the German chemist Justus von Liebig.

Liebig proceeded as follows. Having degreased the inner surface of the flask with a solution of soda - sodium carbonate Na2CO3, he washed it with water, ethyl alcohol C2H5OH and diethyl ether (C2H5)2O. After this, Liebig poured several milliliters of a 10% aqueous solution of formaldehyde HCHO (formalin) into the flask. Having added a solution of ammoniacal silver complex OH to the mixture, he carefully heated the flask, and after a few minutes it became mirror-like (silver was released in the form of a thin coating on the walls of the flask). Subsequently, instead of formalin, Liebig began to use a 10% glucose solution C6H12O6 to obtain a “silver mirror”.

Try to repeat Liebig's experiment, just follow his description exactly.

To prepare a solution of the ammonia complex of silver - diammine silver (I) hydroxide (Ag (NH3)2OH, add a 25% aqueous solution of ammonia NH3 dropwise to a solution of 1 g of silver nitrate AgNO3 in 100 ml of water until the precipitate of silver oxide Ag2O that precipitated initially is not present. will go into solution in the form of a complex salt. In this case the following reactions occur:

2AgNO 3 + 2NH 3 + H20 = Ag 2O ¯ + 2N H4N O3,

Ag2O + 4NH3 + H20 = 2[A g(NH3)2]OH.

The reaction equation for producing a “silver mirror” is as follows:

2OH + HCHO = 2Ag¯ + HCOONH4 + 3NH3 + H20.

The complex cation is reduced to the metal Ag, and formaldehyde HCHO is oxidized to formic acid HCOOH, which in the presence of excess ammonia is converted into a salt - ammonium formate HCOONH4:

HCOOH + NH3 = HCOONH4

Reactions causing the formation of a “silver mirror” were later used for the qualitative detection of aldehydes and glucose in solution, and the solution of a complex silver compound itself was called “Tollens reagent” named after the German chemist Bernhard Tollens, who proposed in 1881 to use this compound in analytical chemistry.

Sparkling Crystals

White light

Try mixing 108 g potassium sulfate and 100 g decahydrate sodium sulfate(Glauber's salt) and add a little hot boiled water in portions while stirring until all the crystals dissolve. Leave the solution in the dark to cool and crystallize the double salt. As soon as crystals begin to separate, the solution will sparkle: at 60 o WITH weakly, and as it cools it gets stronger and stronger. When a lot of crystals fall out, you will see a whole sheaf of sparks. If you run a glass rod over the released crystals at the bottom of the vessel, sparks will appear again. The glow and sparking are caused by the fact that during crystallization double salt composition Na 2 SO 4.

2K 2 SO 4 .

10H 2 O releases a lot of energy, almost completely converted into light. orange light This is also the result of the almost complete conversion of the energy of a chemical reaction into light. To observe it, add it to a saturated aqueous solution. hydroquinone And 10--15% solution potassium carbonate, formalin

perhydrol

. The glow of the liquid is best observed in the dark. The glow is caused by redox reactions of converting hydroquinone into quinone, and formaldehyde into formic acid. At the same time, a reaction of neutralization of formic acid with potassium carbonate occurs, releasing carbon dioxide, and the solution foams. Red prisms 10 g Red prisms dichromate mix potassium with 40 ml of concentrated hydrochloric acid and add 15-20 ml of water. Heat the mixture a little, and the salt crystals will go into solution. After dissolution Cool the potassium solution with water. Very beautiful red prism-shaped crystals fall out, representing potassium salt chlorochromic acid 3 acids KCrO

Cl , according to the reaction equation: K2Cr2O7+2 chlorochromic acid 3 acids HCl

® 2

+ H 2 O . Red precipitate of white matter potassium sulfate Barium sulfate BaSO 4 is a heavy white powder, insoluble in water. This is known to all chemists; this is how it is described in all reference books and books on chemistry. But you took a colorless solution K 2 SO 4 with added violet potassium permanganate KMnO 4, added a solution to it barium chloride and, to their surprise, they discovered that a red precipitate had formed. Washing the red precipitate to remove impurities of potassium permanganate does not give any result; the precipitate remains red. The red precipitate is not pure barium sulfate, but solid solution KMnO 4 in BaSO 4, where part of the sulfate ions is replaced in the crystal lattice of barium sulfate

permanganate ions

Sometimes the most ordinary objects and substances, seemingly well known to us, undergo strange chemical transformations. Who doesn’t know that aluminum cookware lasts for decades? But sometimes amazing things happen to her: she disappears literally before our eyes.

Take an aluminum spoon and thoroughly clean it with fine-grained sandpaper, and then degrease it by dipping it in acetone for 5-10 minutes. (CH3)2CO. After this, dip the spoon for a few seconds in a solution of mercury(II) nitrate containing 3.3 g of Hg (NO3)2 in 100 ml of water. As soon as the surface of the aluminum in the Hg (NO3)2 solution becomes gray, the spoon must be removed, washed with boiled water and dried by blotting, but not wiping, with filter or toilet paper. Miracles will begin before our eyes: the metal spoon will gradually turn into white fluffy flakes, and soon all that will remain from it is an inconspicuous grayish pile of “ash.”

What happened? Aluminum is a chemically active metal. It is usually protected from atmospheric oxygen and moisture by a thin surface film containing oxide and molecular oxygen in a complex chemical combination. By treating the aluminum with mercury salt, we prevented the formation of a new protective film. This happened because, being in a solution of mercury(II) nitrate, aluminum displaces (reduces) metallic mercury from the salt:

2А1 + 3Hg(NO3)2 = 3Hg¯ + 2А1(NO3)3

A l+ Hg = (Al, Hg).

On the cleaned surface of the spoon, a thin layer of aluminum amalgam (an alloy of aluminum and mercury) appears, in which aluminum is crushed to an atomic state. Amalgam does not protect the metal surface from oxidation, and it turns into fluffy flakes of aluminum metahydroxide:

4(A1, Hg) + 2H20 + 3O2 = 4АlO(ОН) ¯ + 4Нg¯

The aluminum consumed in this reaction is replenished with new portions of the metal dissolved in mercury, and the released mercury again “devours” the aluminum. And now, instead of a shiny aluminum spoon, they remain A lO(OH) and tiny droplets of mercury lost in white flakes of aluminum metahydroxide.

If, after a solution of mercury(II) nitrate, an aluminum spoon is immediately immersed in distilled water, then gas bubbles and flakes of a white substance will appear on the surface of the metal. These are hydrogen and aluminum meta-hydroxide:

2A1 + 4H2O = 2AlO(OH) + 3H2.

Aluminum behaves in a similar way in an aqueous solution of copper(II) chloride CuCl2. Try dipping a cleaned and degreased aluminum plate into this solution. You will see brown flakes of copper metal forming and gas bubbles escaping.

The release of copper is understandable - the chemically more active metal aluminum reduces copper from its salts:

2А1 + 3CuCl2 = 3Cu¯ + 2А1С13.

But how to explain the release of gas? It turns out that in this case the protective film does not have time to form on the surface of the aluminum, and it begins to displace hydrogen from the water and turn into aluminum metahydroxide.

Phosphors

The substances from which phosphors are prepared must first be thoroughly purified (for example, by recrystallization) or have a high purity rating (for example, “chemically pure” or “special purity” - “chemically pure” or “extra pure”). Here are recipes for making some glowing compounds.

Purple glow: calcium carbonate (20 g), magnesium carbonate (1.2 g), sodium sulfate (1.0 g), potassium sulfate (1.0 g), sulfur (6.0 g), sucrose (1.0 g), bismuth(III) nitrate (1 ml of 0.5% solution); grind in a porcelain mortar and calcinate at 750-800 °C for 45 minutes.

Green glow: calcium carbonate (20 g), sodium sulfate (1.0 g), sodium tetraborate (0.8 g), sulfur (6.0 g), sucrose (0.8 g), bismuth(III) nitrate (1 ml 5 % solution); grind in a porcelain mortar and calcinate at 800-900 °C for 15 minutes.

Blue-green glow: calcium carbonate (4 g), magnesium carbonate (2 g), strontium carbonate (16 g), sodium sulfate (0.8 g), sodium tetraborate (0.5 g), sulfur (6.0 g), sucrose (0 .3 g), bismuth(III) nitrate (1 ml of 0.5% solution); grind in a porcelain mortar and calcinate at 650-700 °C for 60 minutes.

Blue glow: calcium carbonate (4.0 g), magnesium carbonate (4.0 g), sodium sulfate (1.4 g), zinc oxide (6.0 g), barium sulfide (3.0 g), sulfur (8.0 d), ammonium perchlorate (8.0 g), sucrose (1.0 g); grind in a porcelain mortar (without NH4ClO4), carefully mix with NH4ClO4 and ignite in a gas burner flame for 15 minutes.

Bright green glow: magnesium carbonate (4.0 g), sodium sulfate (2.4 g), zinc oxide (6.0 g), barium sulfide (4.0 g), sulfur (7.0 g), ammonium perchlorate (10.4 g), sucrose (0.8 g); grind in a porcelain mortar (without NH4ClO4), carefully mix with NH4ClO4 and ignite in a gas burner flame for 15 minutes.

Green glow: strontium carbonate (2.0 g), magnesium carbonate (4.0 g), sodium sulfate (2.4 g), zinc oxide (6.0 g), barium sulfide (2.0 g), sulfur (7.0 d), ammonium perchlorate (8.0 g), sucrose (0.8 g); grind in a porcelain mortar (without NH4ClO4), carefully mix with NH4ClO4 and ignite in a gas burner flame for 15 minutes.

The mixtures are illuminated with ultraviolet rays or a camera flash, after which they will glow in the dark.

Phosphors based on boric acid

Equipment: ceramic evaporation cup, boric acid (H3BO3), some component (see below), alcohol lamp, flash.

Place 2 in a steaming cup gr powdered boric acid (sold in a pharmacy) and the same amount of component; add a little water so that when stirred you get a thick paste. Then start heating. First, the mixture will begin to boil, then the water will evaporate and a cake will form, then it will begin to melt, turning into resin. Wait until the whole cake has become thick glassy mass, and then remove the cup from the heat and leave to cool. As soon as the mixture has cooled, when illuminating the resulting phosphor with a flash, you can observe a glow (in absolute darkness).

Ingredients used with boric acid

0.1% fluorescein solution (bright green light)

10% nickel acetate solution (green light)

Citric acid (yellow glow)

Oxalic acid (salad glow)

Fireproof handkerchief

The handkerchief is soaked in a sodium silicate solution, dried and folded. To demonstrate its non-flammability, it is moistened with alcohol and set on fire. The handkerchief must be held flat with crucible tongs. The alcohol burns, but the fabric impregnated with sodium silicate remains unharmed.

Cloud from a flask

An ordinary flask releases a whole cloud of smoke into space. This is how it goes .IN a large flask filled with crystalline potassium carbonate layer 1-2 cm and carefully pour in a 10% aqueous solution ammonia in such an amount that its layer covering the crystals is no thicker than 2 mm. Then pour a little concentrated liquid into the flask in a very thin stream. of hydrochloric acid. A dense stream of thick white smoke escapes from the neck of the flask, which, under its own weight, slides along its outer walls, spreads along the surface of the table and, having reached the edge, slowly falls in flakes to the floor. The appearance of white smoke is caused by reactions:

NH3+ , according to the reaction equation:= NH 4 acids,
K2CO3+2 , according to the reaction equation: = 2KCl+ CO 2 + H 2 O

Aerosol(an air suspension of tiny crystals) of ammonium chloride, which is obtained by the first reaction, is carried away from the flask by carbon dioxide released by the second reaction. Carbon dioxide is heavier than air, which is why the "smoke" falls to the floor.

Fire underwater

In 1808, the English chemist Humphry Davy (1778-1829) was the first to obtain metal magnesium. (At that time, nothing was known about the properties of this metal.) When pieces of the resulting magnesium accidentally caught fire, Davy began to extinguish them with water. There was a flash that burned his face.

Let's make this experience safe. Let's put a transparent plexiglass screen in front of us and put on protective dark glasses (magnesium burns with a dazzling white flame). Place a glass of water behind the screen. Light a little (no more than 2-3 g) Mg magnesium powder in a metal spoon and quickly lower the spoon with burning magnesium into the water. (Naturally, the spoon should have a long handle.)

As soon as the burning magnesium touches the water, it will bubble. The hydrogen released can ignite and burn above the surface of the water. Magnesium in water will burn with an even brighter flame than in air, and the water around it will begin to become cloudy.

This experiment can be carried out in another way. Let's set fire to 2-3 g of magnesium powder in a porcelain cup and then use a long pipette to pour 5-10 ml of water into the cup. There will be a blinding flash immediately.

Magnesium is a chemically active metal. Burning magnesium decomposes water, the hydrogen released ignites in air, and magnesium hydroxide Mg (OH)2 is formed in water:

Mg + 2H20 = Mg (OH)2 + H2.

Burning magnesium cannot be extinguished either by water or sand. After all, sand is silicon dioxide SiO2, which, like water, will interact with burning magnesium to form magnesium oxide and amorphous silicon Si:

SiO2 + 2Mg = Si + 2MgO.

Only asbestos mats and asbestos blankets placed over burning magnesium will extinguish the flames.

Converting red phosphorus to white

A glass rod is lowered into a dry test tube and red phosphorus is added in the amount of half a pea. The bottom of the test tube is heated strongly. White smoke appears first. With further heating, yellowish droplets of white phosphorus appear on the cold inner walls of the test tube. It is also deposited on a glass rod. After heating the test tube stops, the glass rod is removed. White phosphorus on it ignites. Using the end of a glass rod, remove white phosphorus from the inner walls of the test tube. A second outbreak occurs in the air. Conduct the experiment very carefully under a hood!

Sugar is on fire

Take a piece of refined sugar with tongs and try to set it on fire - the sugar does not light up. If you sprinkle this piece with cigarette ashes and then set it on fire with a match, sugar lights up bright blue flame and burns quickly. (The ash contains lithium compounds that act as a catalyst.)

Secret ink

We have to admit that some types of ink have either long since disappeared from use, or are used only for such mysterious purposes as secret correspondence. There are many methods for this type of secret writing, and they all use secret or "sympathetic" ink - colorless or slightly colored liquids. The messages they write become visible only after heating, treatment with special reagents or in ultraviolet or infrared rays. There are many recipes for such ink.

Secret agents of Ivan the Terrible wrote their reports with onion juice. The letters became visible when the paper was heated. Lenin used lemon juice or milk for secret writing. To develop the letter in these cases, it is enough to iron the paper with a hot iron or hold it over the fire for several minutes.

The famous spy Mata Hari also used secret ink. When she was arrested in Paris, a bottle of aqueous solution was found in her hotel room. cobalt chloride, which became one of the evidence in exposing her espionage activities. Cobalt chloride can be successfully used for secret writing: letters written with its solution containing 1 g of salt in 25 ml of water are completely invisible and appear blue when the paper is slightly heated.

Secret ink was widely used in Russia by underground revolutionaries. In 1878, Vera Zasulich shot the St. Petersburg mayor Trepov. Zasulich was acquitted by a jury, but the gendarmes tried to arrest her again as she left the courthouse. However, she managed to escape, informing her friends in advance about the plan to escape at the end of the trial, regardless of its decision. A note with a request to bring some clothes contained information written in an aqueous solution on the back of the sheet ferric chloride FeCl 3 (Zasulich took this substance as a medicine). Such a note can be read by treating it with a cotton swab moistened with a dilute aqueous solution thiocyanate potassium: All invisible letters will turn blood red due to the formation of iron thiocyanate complex.

Members of the secret organization "Black Redistribution" also used invisible ink in their correspondence. But due to the betrayal of one of Chernoperedel'tsy, who knew the secret of deciphering the letters, almost everyone was arrested... The secret letters were written with a dilute aqueous solution copper sulfate. Text written in such ink appeared if the paper was held over a bottle with ammonia. The letters turn bright blue due to the formation of an ammonia complex of copper.

But the Chinese emperor Qing Shi Huangdi (249-206 BC), during whose reign the Great Wall of China appeared, used thick rice water for his secret letters, which, after the written hieroglyphs dried, did not leave any visible traces. If such a letter is slightly moistened with a weak alcohol solution iodine, then blue letters appear. And the emperor used a brown decoction of seaweed, apparently containing iodine, to develop writing.

Another secret ink recipe involves using a 10% aqueous solution yellow blood salt. Letters written with this solution disappear when the paper dries. To see the inscription, you need to moisten the paper with a 40% solution ferric chloride. The bright blue letters that appear during this treatment no longer disappear when dry. The appearance of letters is associated with the formation of a complex compound known as “Turnboole blue.”

Remember the story of the disappearance of Fantômas' note? Vanishing ink can be prepared by mixing 50 ml of alcohol tincture of iodine with a teaspoon dextrin and filter off the precipitate. Such blue ink completely loses its color after 1-2 days due to volatilization of iodine.

Synthesis of Berthollet salt

Will come in handy for your unforgettable experiences.

Equipment: 50% potassium hydroxide solution (KOH), potassium permanganate (KMnO4), concentrated hydrochloric acid (density = 1.19 g per cubic cm), nitric acid,

solution of silver nitrate (AgNO3), a device for producing chlorine (with a wide gas outlet tube), a beaker, two test tubes, a glass funnel, a filter, an iron stand, a burner. The experiment is carried out in a fume hood or in the open air.

Assemble a device for producing chlorine. Pour potassium permanganate (1 cm layer) into the reaction flask, fill the dropping funnel with concentrated hydrochloric acid and insert it into the flask (make sure everything is sealed). Pour 30 - 40 ml of a 50% solution of potassium hydroxide into a beaker and heat it almost to a boil (70 - 80 degrees) on an asbestos grid. Make chlorine by carefully (drop by drop) adding hydrochloric acid to potassium permanganate (CRAC!). There should be a uniform slow flow of chlorine through the gas outlet tube.

Immerse the end of the gas vent in a hot alkali solution and pass a current of chlorine. Within 5-6 minutes. White plastic crystals of Berthollet salt will begin to fall out of the solution.

3Cl2 + 6KOH = KClO3 + 5KCl + 3H2O.

Cleaning from chlorine ions:

Allow the solution to cool, filter out the precipitated crystals, rinse them with water on a filter and test part of the filtrate for the presence of chlorine ions. To do this, add a little nitric acid and a little silver nitrate to the filtrate. If a cheesy precipitate of silver chloride, insoluble in nitric acid, precipitates, continue washing the filtrate until the reaction for Cl ion is negative.

Synthesis of pyrophoric iron

Equipment: test tubes, funnels, filter paper, ferrous sulfate (FeSO4), ammonium oxalate.

Pyrophoric iron should not be stored as it can cause a fire. Pyrophoric iron is prepared by combining equimolar solutions of ammonium oxalate and iron (II) sulfate or Mohr's salt. To prepare solutions, take 20 g of Mohr's Salts and dissolve it in 20 ml.

water. Ammonium oxalate in the amount of 7.2 g is also dissolved in 20 ml.

water. Drain the solutions together. A precipitate of iron oxalate dihydrate (FeC2O4 * 2H2O) will form. Filter the precipitate and wash thoroughly to remove ammonium salts.

Dry the washed precipitate with filter paper and transfer it to a test tube. Place the test tube in a stand at an angle with the hole slightly downwards. Heat the substance carefully in the flame of the burner, remove any drops of water that appear with filter paper. When the substance decomposes and turns into a black powder, close the test tube. Place the test tube with pyrophoric iron to cool in a safe place away from flammable substances. When iron or asbestos is spilled onto a sheet, pyrophoric iron ignites. The experience is very effective. Spontaneous combustion is explained by very thin

fineness

, large oxidation surface. Therefore, after the experiment, the remaining iron must be eliminated.

Charcoal from sugar

Pour 50 ml of ethyl alcohol into a measuring cylinder. Through a pipette that is lowered to the bottom of the cylinder, introduce 40 ml of concentrated sulfuric acid. Thus, two layers of liquid with a clearly visible boundary are formed in the cylinder: the upper layer is alcohol, the lower layer is sulfuric acid. We throw a few small crystals of potassium permanganate into the cylinder. Having reached the interface, the crystals begin to flare up - here we have fireworks. The appearance of outbreaks is due to the fact that upon contact with sulfuric acid, manganese anhydride is formed on the surface of salt crystals Mn 2 O 7 is a strong oxidizing agent that sets fire to a small amount of alcohol:<

acidify the potassium chromate solution with H 2 SO 4 (orange color);<

lead nitrate and potassium iodide (yellow);<

nickel(II) sulfate and sodium hydroxide (green);<

copper(II) sulfate and sodium hydroxide (blue);<

copper(II) sulfate and ammonia solution (blue);<

cobalt(II) chloride and potassium thiocyanate (purple).<

1. FeCl 3 + 3KCNS® Fe(CNS) 3 + 3KCl
2. 2K 2 CrO 4 + H 2 SO 4® K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O
3. Pb (NO 3) 2 + 2KJ® PbJ 2 + 2KNO 3
4. NiSO 4 + 2NaOH® Ni(OH) 2 + Na 2 SO 4
5. CuSO 4 + 2NaOH® Cu(OH) 2 + 2Na 2 SO 4
6. CuSO 4 + 4NH 3® SO 4
7. CoCl 2 + 2KCNS® Co(CNS) 2 + 2KCl

Chemical algae

A solution of silicate glue (sodium silicate) diluted with an equal volume of water is poured into a glass. Crystals of chlorides of calcium, manganese (II), cobalt (II), nickel (II) and other metals are thrown into the bottom of the glass. After some time, crystals of the corresponding sparingly soluble silicates that resemble algae.

Chemical clock

Equipment: 4 g of food grade citric acid, two flints for lighters (contain cerium compounds (III and IV), 12 ml of sulfuric acid solution (1:2), 1.7 g of potassium bromate KBrO3.

Prepare 2 solutions. In the first case, dissolve two lighter flints in sulfuric acid. In the second - in 10 ml. Dissolve citric acid in hot water and pour potassium bromate into it. To completely dissolve the substances, heat the mixture slightly. Quickly pour the prepared solutions together and stir with a glass rod. A light yellow color appears, which after 20 seconds. Changes to, but after 20 seconds. turns yellow again. At a temperature of 45 degrees, such a change can be observed within 2 minutes. Then the solution becomes cloudy, bubbles of carbon monoxide (IV) begin to appear, and the intervals of alternating color of the solution gradually increase in a strictly defined sequence: each next interval is 10-15 seconds longer than the previous one.

There is another recipe: dissolve 2 g of citric acid in 6 ml.

in water, add 0.2 g of potassium bromate and 0.7 ml. concentrated H2SO4. Add water to the mixture to a volume of 10 ml, then add 0.04 g of potassium permanganate (KMnO4) and mix thoroughly until the salt is completely dissolved. There is a periodic change in the color of the solution. The mechanism of chemical reactions can be explained asoxidatively- restorative

a process in which bromic acid plays the role of an oxidizing agent and citric acid acts as a reducing agent:

KBrO3 + H2SO4 = KHSO4 + HBrO3

9HBrO3 + 2C6H8O7 = 9HBrO + 8H2O + 12CO2

9HBrO + C6H8O7 = 9HBr + 4H2O + 6CO2

The color of the solution changes under the influence of catalysts - cerium and manganese compounds, which in turn also change the oxidation state, but up to a certain ion concentration, after which the reverse process occurs.

Chemical vacuum in a bottle Fill the flask with carbon dioxide. Pour a little concentrated solution into it Heidelberg hydroxide

University Friedrich Wöhler, mixing aqueous solutions of ammonium thiocyanate NH 4 NCS and mercuric nitrate Hg (NO 3) 2, discovered that a white precipitate precipitated from the solution. Wöhler filtered the solution and dried the precipitate of the resulting mercury thiocyanate Hg (NCS) 2, and then, out of curiosity, set it on fire. The sediment caught fire and a miracle happened: from a nondescript white lump, a long black and yellow “snake” crawled out and grew. After ignition, mercury thiocyanate quickly decomposes to form black mercury sulfide HgS, yellow bulky carbon nitride of the composition C 3 N 4, carbon dioxide and sulfur dioxide. The rapidly released gases cause the snake, consisting of solid reaction products, to “crawl.” It is simply amazing that from 1 g of ammonium thiocyanate and 2.5 g of mercury nitrate, in skillful hands a snake 20-30 cm long is obtained. However, mercury salts are poisonous, and working with them requires caution and attention. It is safer to show a dichromatic snake.

Dichromate snake Mix and then grind in a mortar 10 g potassium dichromate K 2 Cr 2 O 7.5 g potassium nitrate KNO 3 and 10 g. The resulting powder is moistened with ethyl alcohol and collodion and pressed into a glass tube with a diameter of 4-5 mm. The result is a “stick” of the mixture, which, when ignited, forms first a black and then a green snake, which crawls out and wriggles in the same way as a thiocyanate snake: it burns at a speed of 2 mm per second and lengthens 10 times! The combustion reaction of sucrose in the presence of two oxidizing agents - potassium nitrate and potassium dichromate - is quite complex; the end result is black soot particles, green chromium oxide, molten potassium carbonate, as well as carbon dioxide and nitrogen. Gases swell a mixture of solids and cause it to move.

Another recipe for making dichromate snake involves mixing 1g powders ammonium dichromate(NH 4) 2 Cr 2 O 7, 2 g ammonium nitrate NH 4 NO 3 and 1 g of powdered sugar. This mixture is moistened with water, a stick is molded from it and air dried. If you set a stick on fire, black and green snakes will crawl out of it in different directions. The reaction products here are the same as in the previous recipe

Nitrate worm

Pour 3-4 tablespoons of sifted river sand into a dining plate, make a slide out of it with a depression at the top and prepare a reaction mixture consisting of 1/2 teaspoon ammonium nitrate and 1/2 teaspoon granulated sugar, thoroughly ground in a mortar. Then pour another 1/2 tablespoon into the depression of the slide. ethyl alcohol and add 1 teaspoon of prepared nitrate-sugar mixtures. After this, all that remains is to set the alcohol on fire. Immediately, black balls of charred granulated sugar appear on the surface of the mixture, and after them a black shiny and thick “worm” grows, descending from the slide. If nitrate-sugar if no more than 1 teaspoon of the mixture was taken, then the length of the worm will not exceed 3-4 cm. And its thickness depends on the diameter of the recess of the slide.

Alcohol and gluconate snakes

These are the simplest recipes from our chemical serpentarium. If the pill solid alcohol(dry fuel) soak in a concentrated aqueous solution ammonium nitrate, dripping it from a pipette, and then dry it, then after three or four times By repeating these operations, you can obtain the raw material for the alcohol snake. The ignited tablet swells; snake color is black. The decomposition of methenamine (CH 2 ) 6 N 4 , which is part of solid alcohol, in a mixture with ammonium nitrate, leads to the formation of carbon, carbon dioxide, nitrogen and water.

To get a gluconate snake, just bring the tablet to the flame gluconate calcium, which is sold in every pharmacy. A snake will crawl out of the tablet, the volume of which is much greater than the volume of the original substance. Decomposition of calcium gluconate having the composition Ca 2.

H 2 O leads to the formation of calcium oxide, carbon, carbon dioxide and water.

Flapping stripes

Equipment: filter paper, alcohol solution of iodine, 25% ammonia solution, glass rod, sheet of tin (plywood), glass.

Place the filter paper in a glass with a mixture of iodine and ammonia solution (1:1). Cut the wet paper into thin strips and place them on a sheet of tin to dry; they will dry for about a day. When you touch the dangerous strips with a glass rod, there will be a bang and a shot. Pure nitrogen iodide is not formed here, but its molecular compound with ammonia NI3*NH3 is formed. In nitrogen iodide, nitrogen has an oxidation state of -3, and iodine has an oxidation state of +1. The positive oxidation state of iodine forms a very weak bond with nitrogen. Substance thermodynamically

unstable, therefore, upon explosion, it decomposes with the formation of iodine vapor and free nitrogen:

This is also an amalgam!

It is known that the formation of amalgam is a property inherent in many metals. However, this time we are talking about amalgam... ammonium!

A concentrated aqueous solution of ammonium chloride NH4Cl is poured into a glass cylinder placed on a large porcelain plate up to half its height. 10-15 g of liquid sodium amalgam (Na, Hg) are added to the solution. The chemical reaction immediately begins to form ammonium amalgam, a very unstable substance that quickly decomposes into mercury Hg, ammonia NH, and hydrogen H2. The released hydrogen swells the amalgam, and the spongy gray mass slowly crawls out of the cylinder onto the plate. This spectacular spectacle is associated with two reactions: acids(Na, Hg) + NH 4 = (NH 4+, Hg -) +

NaCl

2(NH4+, Hg -) = 2NH3 + 2Hg + H2