Target: To increase the cognitive activity of students in chemistry, through the demonstration of its entertaining side.
Tasks:
Emphasize the importance of chemistry in human life and activity.
Continue to introduce students to chemistry.
Education of compliance with safety rules, on the example of performing demonstration experiments
Location of the event : cabinet of chemistry and biology.
Equipment: stand with test tubes, conical flask, chemical beakers, matches, glass rods, laboratory stand, scalpel, cotton wool,sandpaper, iron knifeporcelain cup, torch.
Reagents:
Sodium carbonate, ethyl alcohol, solutionNH 3 10% and 25%,hydrogen peroxide solutionhydrochloric acid (conc.), sulfuric acid (conc.), powdered sugar, magnesium powder, calcium chloride 10% solution, barium chloride 10% solution, magnesium sulfate 10% solution, iron (III) chloride, potassium thiocyanate 5% solution, potassium nitrate (sat. solution), copper(2) sulfate, potassium dichromate, sodium hydroxideor potassium20% solution, weakiodine solution,phenolphtolein solution,potassium chromate, metallic sodium,crystalline potassium permanganate, sulfuric acid 10% solution, lithium fluoride,sodium chloride, strontium or lithium nitrate, potassium chloride, barium nitrate, boric acid.
Preparation for the event: Before the start of the event, the roles were distributed among the students of the 11th grade, all the experiments were done in advance. Primary and middle school students are invited.
Literature:
VA Aleksinsky Entertaining experiments in chemistry A book for teachers. M.: Education, 1995.
GI Shtrempler Chemistry at leisure. Riddles, games, puzzles. Book for students M .: Education, 1993.
M. Yugorkovenko. Lesson developments in chemistry: 8th grade. - M .: VAKO, 2007.
Entertaining tasks and spectacular experiments in chemistry / B.D. Stepin, L.Yu. Alikberova. – M.: Bustard, 2006.
P. Khomchenko, F.P. Platonov, I.N. Chertkov Demonstration experiment in chemistry. A guide for teachers. Moscow: Education, 1978.
Event progress:
Introductory speech of the teacher:
Welcome to Chemistry Evening hosted by Year 11 students.
Chemistry is an amazing science. Everyone needs it: a cook, a driver, a gardener, a builder and many others. On the one hand, it is very specific and deals with countless useful and harmful substances around us. On the other hand, this science is abstract: it studies the smallest particles that you cannot see in the most powerful microscope, considers formidable formulas and complex laws.
Now 11th grade students Tanya Kinzhibaeva, Zaira Omarova, Anna Zuzova and Dasha Ponomarenko will conduct and show a series of demonstration experiments that will open for you the beautiful and mysterious side of chemistry ... "
Dasha: Well, of course, without a doubt, we must learn chemistry,
Without knowledge of all phenomena It is impossible to live today.
Tanya: We need to do better, friends, in teaching
And you should not sigh That chemistry is torment!
Zaire: If they didn’t know chemistry, they would always stomp on foot:
The bus will never run without fuel!
Anya: So that we grow up normally, Strong and strong,
Vitamins are also produced by our chemistry!
Dasha: For plants to grow, Substances were invented.
It would be nice for us to be like this - Big ones would quickly grow up.
Tanya: Rubber is rare in nature, You can't live without it.
We would walk through puddles In felt boots and without galoshes!
Zaire: Widely entered our everyday life Various plastics
In a very short time they were recognized by the masses!
Anya: Polymer let, for hair, Stimulating growth,
They will invent as soon as possible Then the braids will grow.
Experiences:
Anya: Experience #1 Description:
There is no smoke without fire, says an old Russian proverb. It turns out that with the help of chemistry you can get smoke without fire. And so, attention!Flask cloud:
The participant of the evening takes two glass rods, on which a little cotton wool is wound, and wets them: one in concentrated nitric (or hydrochloric) acid, the other in an aqueous 25% ammonia solution. Sticks should be brought to each other. White smoke rises from the sticks.
Essence of experience– formation of nitrate (chloride) ammonium.
Tanya: Experience #2 Description:
The participant of the evening pours conc. into one glass beaker (cylinder). hydrochloric acid, and in the other - 25% ammonia solution. Close both cylinders with lids and place them at a certain distance from each other. Before the experiment, show that the cylinders are "empty". During the demonstration of the experiment, the cylinder with hydrochloric acid on the walls is turned upside down and placed on the lid of the cylinder with ammonia. Remove the lid: white smoke is formed - a sign of a chemical reaction.
Zaire: Experience No. 3 Description:
Pour 2 teaspoons of calcium chloride CaCl into one glass 2 , and in the other - the same amount of sodium carbonateNa 2 C0 3 and pour into each glass of water about 1/4 of their volume. Then the resulting solutions are poured together, and the liquid becomes white, like milk. This experience must be demonstrated quickly, since calcium carbonate CaCO 3 precipitates and viewers may notice that it is not milk at all. But if you add an excess of hydrochloric acid to the mixture, then the “milk”, having boiled, instantly turns into “sparkling water”.
If to a dilute aqueous solution of barium chloride BaCl 2 add a solution of potassium or magnesium sulfate, a white precipitate of barium sulfate is formedBaS0 4 similar to cottage cheese.
With some special chemical knowledge you can go from one juice to another Orange, lemon, apple.
Tanya: Experience No. 4 Description:
First, we show the audience a glass with a solution of potassium dichromate, which is orange. Then, adding alkali, we turn the "orange juice" into "lemon". Then we do the opposite: from “lemon juice” - “orange”, for this we add a little sulfuric acid, then add a little hydrogen peroxide solution and the “juice” becomes “apple”.
Dasha: What methods of making fire do you know?Examples are given from the audience.Let's try to do without these funds. On a hike, a situation may arise in which the matches get wet, the lighter is broken or lost, but this is not a hindrance for a person familiar with chemistry, he can light a fire without matches or a lighter. Now I will show you how to do it.
Anya: Experience number 5.Campfire without matches
Description:Participant of the eveningmakes a pea-sized mixture of crystalline potassium permanganate and concentrated sulfuric acid. We place the mixture in a porcelain cup and put a splinter (firewood) on top of it, so that they do not touch the mixture. Wet the cotton wool with plenty of alcohol and squeeze a drop of alcohol onto the mixture. The fire lights up.
Essence of experience- there is a vigorous oxidation of alcohol by oxygen, which is released during the interaction of sulfuric acid with potassium permanganate. The heat released during this reaction ignites the fire.
Zaire: Experience number 6."Golden Knife"
Description:Prepare an iron knife cleaned with sandpaper. Immerse this knife in a concentrated solution of copper sulfate. The knife becomes golden.
Anya: Experience number 7. "Getting wine and milk." Description:
Getting wine - the interaction of phenolphthalein and alkali;
milk production - the interaction of sulfuric acid and barium chloride.
Dasha: Experience number 8.Description:
The participant of the evening pours icing sugar (30 g) into a glass placed on a saucer, pours 26 ml of concentrated sulfuric acid into the same place and stirs the mixture with a glass rod. After 1-1.5 minutes, the mixture in the glass darkens, swells and rises above the edges of the glass in the form of a loose mass.
Essence of experienceSulfuric acid removes water from sugar molecules, oxidizes carbon into carbon dioxide, and simultaneously sulfur dioxide is formed. The released gases push the mass out of the glass.
Tanya: Experience number 9. Description:
The participant of the evening puts cotton swabs moistened with ethyl alcohol into porcelain cups. On the surface of the tampons, he pours the following salts: sodium chloride, strontium nitrate (or lithium nitrate), potassium chloride, barium nitrate (or boric acid). On a metal board or on a piece of glass, the participant prepares a mixture (slurry) of potassium permanganate and concentrated sulfuric acid. He takes some of this mass with a glass rod and touches the surface of the tampons. Tampons flash and burn in different colors: yellow, red, purple, green.
Essence of experience– alkali and alkaline earth metal ions color the flame in different colors.
Dear children, I am so tired and hungry that I ask you to allow me to eat a little.
Anya: The host addresses the participant of the evening: - Give me, please, tea and crackers.
The participant of the evening gives the host a glass of tea and a white cracker.
The host moistens the cracker in tea - the cracker turns blue.
Leading: - Disgrace, you almost poisoned me!
Participant of the evening:- Excuse me, I must have mixed up the glasses.
Essence of experience- in a glass was a solution of iodine. The starch in the bread turned blue.
Tanya: Experiment No. 10. Runs - dissolves, and stops - explodes (chemical riddle) Description: Place metallic sodium purified from oxide films in a Petri dish with water. A piece of sodium "runs", decreases in volume and gradually disappears. After adding a solution of phenolphtolein, a crimson color appears, which is characteristic of alkalis.
(Zaire) By the name of Vulcan, the god of fire of the ancient Romans, fire-breathing mountains are named - volcanoes that suddenly wake up and destroy all life around during terrible eruptions. Chemists also invented their own home volcanoes, the most famous of which was made by the German chemist Rudolf Böttger. He received an orange-red substance and decided to test it for its ability to ignite from a hot splinter. Let's see what happened
Zaire: Experience number 11.Böttger Volcano:Description:
Pour a little potassium dichromate into a porcelain cup, then add a little magnesium powder, mix well and form a slide in the cup. We touch the top of the "volcano" with a burning torch. The burning mixture emits a large number of sparks, it is reminiscent of a volcanic eruption. The volcano itself is constantly growing and changing color, from orange to green.
Dasha: Experience number 12. Description:
"Martian landscape".On the poster, write in advance with phenolphthalein “chemistry is an amazing science”, and then, when showing the experiment, wipe the colorless inscription with a swab moistened with alkali. The inscription will turn purple.
Yes, it turns out that everything can burn, but, however, not everything can burn.
Tanya: Experience number 12."Fireproof scarf".Description:
Rinse the handkerchief in water, then squeeze lightly and soak well with alcohol. Grab the handkerchief with crucible tongs and set it on fire. The alcohol will ignite, but the handkerchief will not burn.
Surgery. Some chemists have learned how to work real miracles, with the help of the living water they have made, they heal wounds.
Anya: Experience number 13. "Chameleon".
Description: Pour a solution of potassium chromate into a glass, acidifying with a few drops of sulfuric acid. While stirring the solution with a glass rod, pour in the hydrogen peroxide solution: a blue color appears, which soon turns green.
We operate without pain, however, there will be a lot of blood.
(Dasha reads a poem, Zaira conducts an experiment)
Every operation requires sterilization.
We moisten with iodine abundantly so that everything is sterile.
Don't move, patient! Give me the knife, assistant!
Look, it's blood flowing in a stream, not water.
But now I will wipe my hand - from the cut - not a trace!
Zaire: Experience number 14. "Wounding and Healing".
Description:Solutions of iron(III) chloride, potassium thiocyanate, and lithium fluoride were prepared in advance. We chose a volunteer, moisten a cotton swab with "alcohol" (potassium thiocyanate) and rubbed his hand, then disinfected the scalpel with a solution of "iodine" (iron chloride (III)). They ran a “scalpel” over the area of skin treated with “alcohol”, and “blood” flowed. After that, we "heal the wound", for this we moisten the cotton wool in "living water" (lithium fluoride solution). The "blood" will disappear, and under it - healthy skin.
We have shown you only some of the wonders of chemistry. And we want to end our chemical fireworks with the anthem of chemists:
We are destined to shed all that flows.
Spill what cannot be spilled!
Our office is called chemical!
We were born to love chemistry!
Higher and higher and higher
Flies red bromine to heaven
And who will breathe this bromine,
That redhead becomes himself!
Closure:
Tanya: Thank you for your attention. Our chemistry evening is coming to an end. Guys, we hope that you liked everything and you took a different look at this complex and sometimes boring science.
See you soon dear guys!
The text of the work is placed without images and formulas.
The full version of the work is available in the "Job Files" tab in PDF format
Introduction 3
Theoretical part 5
History of opening indicators 5
Classification of school indicators and how to use them 6
pH 6
Experimental part 8
Sociological survey 8
Preparation of the indicator from natural material 9
Laboratory study "Measuring the pH level in cleansers"………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
Conclusion 14
List of used sources 15
Introduction
In the modern world, it is almost impossible to do without cosmetics. Soaps, shampoos, scrubs, lotions, tonics, creams... It's hard for us to imagine our life without it. Cosmetics accompanies our life from birth. On the shelves of shops there are a lot of products from different manufacturers: UNILEVER, Beiersdorf, Oriflame, etc. Manufacturers - both domestic and foreign - vying with each other offer new products, praising their wonderful properties. Cosmetics can be used from an early age (for example, Jonson's Baby, Bubchen are intended for children). The main purpose of modern cosmetics is to give people the opportunity to remain beautiful all their lives. Every morning we wash ourselves with special cosmetics, while our grandmothers washed with spring water. Otherwise, it’s impossible: we live in completely different environmental conditions. Water will not dissolve the sweat-fat secretions of the skin mixed with dust and city exhausts. In addition, our tap water is with bleach. And ordinary soap is alkali, it will dry out the skin It is necessary to use special cleansers that contain softer substances compared to soap, and in addition to cleansing, take care of the skin, taking into account its type.
Having bought unsuitable clothes or shoes, you can easily return them back to the store. With cosmetics, this, alas, is impossible. In order not to be embarrassed to tears because of an unsuccessful remedy, you need to choose cosmetics more carefully. One of the important guidelines when choosing a cosmetic product is the pH value.
Having learned to determine the pH, we will be able to make cosmetics at home using only environmentally friendly natural ingredients. To determine the pH, special indicators or test strips are needed. 0000000 Target: making an indicator at home; determination of the quality of various cleansers using an indicator.
Research objectives:
Conduct an analysis of the scientific literature on this issue;
Learn the history of the appearance of indicators;
To study the ways of formation of indicators;
Prepare indicators from natural materials at home;
Conduct analysis of cosmetics, make a video of research
Hypothesis: suppose that indicators can be prepared at home.
Object of study: indicators
Subject of study: composition of indicators
Methods: analysis of scientific literature, observation, laboratory experiment, experience, questioning, analysis of the results.
Theoretical part
History of opening indicators
Indicators means "pointers". These are substances that change color depending on whether they are in an acidic, alkaline or neutral environment. The most common indicators are litmus, phenolphthalein, methyl orange.
The first acid-base indicator was litmus. Litmus is an aqueous infusion of a litmus lichen that grows on rocks in Scotland.
Indicators were first discovered in the 17th century by the English physicist and chemist Robert Boyle. Boyle conducted various experiments. One day, when he was conducting another study, a gardener came in. He brought violets. Boyle loved flowers, but he needed to experiment. Boyle left the flowers on the table. When the scientist finished his experiment, he accidentally looked at the flowers, they were smoking. To save the flowers, he dipped them into a glass of water. And - what a miracle - violets, their dark purple petals, turned red. Boyle became interested and experimented with solutions, adding violets each time and observing what happened to the flowers. In some glasses, the flowers immediately began to turn red. The scientist realized that the color of violets depends on what solution is in the glass, what substances are contained in the solution. The best results were given by experiments with litmus lichen. Boyle dipped ordinary paper strips into the infusion of litmus lichen. I waited until they were saturated with infusion, and then dried them. These cunning pieces of paper Robert Boyle called indicators, which in Latin means "pointer", as they indicate the medium of the solution. It was the indicators that helped the scientist to discover a new acid - phosphoric, which he obtained by burning phosphorus and dissolving the resulting white product in water.
If there are no real chemical indicators, home, field and garden flowers and even the juice of many berries - cherries, chokeberries, currants - can be successfully used to determine the acidity of the environment. Pink, crimson or red geranium flowers, peony petals or colored peas will turn blue when dipped in an alkaline solution. Cherry and currant juice will also turn blue in an alkaline environment. On the contrary, in acid the same “reagents” will take on a pink-red color.
Plant acid-base indicators here are coloring substances - anthocyanins. It is anthocyanins that give various shades of pink, red, blue and purple to many flowers and fruits.
Beet dye betaine or betanidine in an alkaline environment becomes colorless, and in an acidic environment it turns red. That is why borscht with sauerkraut has such an appetizing color.
Classification of school indicators and how to use them.
Indicators have different classifications . One of the most common is acid-base indicators, which change color depending on the acidity of the solution. Nowadays, several hundred artificially synthesized acid-base indicators are known, some of which can be found in the school chemistry laboratory.
Phenolphthalein (sold in a pharmacy called "purgen") - white or white with a slightly yellowish tint fine crystalline powder. Soluble in 95% alcohol, practically insoluble in water. Colorless phenolphthalein is colorless in an acidic and neutral environment, and in an alkaline environment it turns crimson. Therefore, phenolphthalein is used to determine the alkaline environment.
methyl orange - orange crystalline powder. Sparingly soluble in water, freely soluble in hot water, practically insoluble in organic solvents. The color of the solution changes from red to yellow.
Lakmoid (litmus) - black powder. Soluble in water, 95% alcohol, acetone, glacial acetic acid. The color of the solution changes from red to blue.
Indicators are usually used by adding a few drops of an aqueous or alcoholic solution, or a little powder to the test solution.
Another method of application is the use of strips of paper impregnated with an indicator solution or a mixture of indicators and dried at room temperature. Such strips are produced in a wide variety of versions - with or without a color scale printed on them - a color standard.
Hydrogen indicator
The indicator paper universal has a scale for definition of the environment (рН).
Hydrogen index, pH - a value that characterizes the concentration of hydrogen ions in solutions. This concept was introduced in 1909 by the Danish chemist Sorensen. The indicator is called pH, according to the first letters of Latin words potentia hydrogeni is the strength of hydrogen, or pondus hydrogenii is the weight of hydrogen. Aqueous solutions may have a pH value in the range of 0-14. In pure water and neutral solutions pH=7, in acidic solutions pH7. pH values are measured using acid-base indicators.
Table 1. - Color of the indicator in various environments.
Initiation into chemists
The proposed extra-curricular event I hold as a theatrical performance, in which not only high school students participate, but also students who begin to study a chemistry course. It is recommended to hold this holiday at the end of the first - the beginning of the second quarter, when eighth graders have already learned some of the basics of the subject.
Characters: presenter, Winnie the Pooh, Rabbit, Piglet, Wizard Chemist, assistants
(2-3 people).
The presenter appears on the stage, he addresses the audience.
Leading. « I want to be a chemist!" - this is how the high school student Justus Liebig answered the question of the director of the Darmstadt Gymnasium about choosing a future profession. This evoked laughter from the teachers and schoolchildren present at the conversation. The fact is that at the beginning of the XIX century. in Germany and in most other countries such a profession was not taken seriously. Chemistry was considered as an applied part of natural science.
Nowadays, the desire to become a chemist does not make anyone laugh, on the contrary, the chemical industry is constantly in need of people who combine extensive knowledge and experimental skills with a love of chemistry. Friends, would you like to become real chemists?
Students from the audience respond to the facilitator.
Leading. Of course yes! I didn't doubt it. Chemistry is the science of substances and their transformations. To know the properties of substances is necessary to find their application. Although you have recently begun to study chemistry, I am sure that you have already become familiar with many substances. Name the substances you know.
The response of the students from the audience.
Leading. So we start the holiday. I urge you to carefully observe everything that happens on the stage, actively participate in all games and competitions. And only then will we be able to light the “chemical fire” and introduce you to the title of “Chemist”.
Winnie the Pooh appears on the stage (he holds a flask with water in one hand, and a piece of chalk in the other), Piglet runs after him, stumbling.
Winnie the Pooh(sings).
Who loves to study chemistry
He acts wisely
To create any miracle
It's easy then.
Here is the flask(shows the flask to the audience), Yes Yes Yes(scratching at the back of the head). I do it in her! Here is the chalk(shows the audience a piece of chalk) and here is the water(throws chalk into a flask of water). What happened? Nonsense! How nonsense? No, there's something wrong! We must try again.(He is going to repeat the experiment, but then Piglet catches up with him and pulls his hand.)
Piglet. Winnie, Winnie...
Winnie the Pooh. What happened, Piglet?
Piglet. Explain what are you doing? Where are you in such a hurry? I just can't keep up with you.
Winnie the Pooh. Piglet, I decided to become a famous chemist. See, I already know it's a flask(shows the flask to Piglet) , and in the flask a mixture of chalk and water. And now I'm going to Rabbit to tell me what else I need to do to become a great and famous chemist..
Piglet. And chemistry, what is it about?
Winnie the Pooh(thinking). Chemistry is ... But you better listen.
A group of students sings a song to the tune of "Little Country".
students.
The chemistry of all queens is science,
Chemistry is the most important.
Synthesis of various components -
It is under her control.
Can help a sick person in need
And create a miracle
Can keep you warm in cold winters
We can't live without her.
Chorus.Chemistry, chemistry
You are important to people.
Chemistry is our future
There is no life without you.
You subjugated all the elements:
Water, metal, fire.
Without oxygen there is no life in the world,
Neon gives us light.
"Ferrum" is in the cells
blood,
Without “ash-two-o” we cannot live.
Chemistry at school is studied,
To devote his life to her.
Chorus.Chemistry is me
Chemistry is my life.
Chemistry is our future
There is no life without you.
Winnie the Pooh. Well, Piglet, did you understand everything? Will you come with me to the Rabbit?
Piglet. Yes, Vinnie, I understand everything, I'm going with you! Oh, here comes the Rabbit.
Rabbit enters the scene.
Rabbit. Hello Vinnie! Hello Piglet! Hello guys! I hear you are talking about chemistry. Do you know(raises index finger) that chemistry is an interesting science?! Chemistry appeared in antiquity, and the most prominent chemists of the ancient world were representatives of Egypt. Even the word "chemistry", according to scientists, appeared in Egypt. The first thing that testifies to how highly developed chemistry was there is the art of the Egyptians to embalm corpses, which is a mystery that has not been fully solved by scientists to this day. Despite the fact that modern scientists have hundreds of thousands of substances, they cannot make a mummy exactly as they did in the time of the pharaohs.
The second area where the Egyptians achieved great perfection is paint. Thousands of years have passed since objects were painted in Egypt, and paints have retained their brightness and strength to this day.
The Egyptians developed both perfumery and the ability to manufacture cosmetic substances. For example, they knew how to prepare black eyebrow dye, various fragrant ointments and oils, fragrant waters.
For 1600 years BC. e. the Egyptians knew the production of papyri, which they even exported to other countries. In the production of these papyri lies some kind of mystery that modern scientists cannot solve. How were individual sheets of papyrus glued together? What kind of glue was it, which did not allow the sheets to crumble even after several millennia?
Of course, the Egyptians did not have a real science, but it must be said that in some cases they had more correct views on the chemical nature of substances than even the alchemists who lived thousands of years after them. All Egyptian science, including nascent chemistry, was considered sacred. It was available only to the elite: only the priests were engaged in it. Science was the secret of the ruling class and was guarded like a valuable treasure. But still, some inquisitive foreigners managed to enter into the confidence of the Egyptians and find out from them some of the secrets of Egyptian science. These were the Greek sages Solon, Pythagoras, Democritus, Herodotus and Plato. Through them, Greece borrowed chemical knowledge from the Egyptians.
Winnie the Pooh. And I know that together with the Egyptians, the most prominent people of the Ancient East must be considered the Babylonians. They knew metals as well as the Egyptians, how they were obtained and processed.
The Babylonians knew how to make alcoholic drinks from palm fruits. They also knew the chemical methods of water disinfection, having no idea about bacteria as pathogens.
The Phoenicians - these ancient navigators - borrowed chemical knowledge from those peoples with whom they traded. They also spread this knowledge throughout the countries of the East and along the shores of the Mediterranean Sea.
There is a legend that the Phoenicians invented glass. The Roman historian Pliny has a story about how Phoenician sailors carried soda on their ship and landed on the banks of a river in Palestine. When building a hearth for cooking, they needed stones, but there were no stones anywhere. Then the sailors used pieces of soda to build a hearth. The fire flared up and reached great strength. Suddenly, the sailors saw that the soda had melted and, together with the sand, had formed a transparent, viscous mass. This mass froze, and the sailors saw solid transparent pieces. Thus, a method for making glass was discovered. The inhabitants of the area where the Phoenicians stopped improved the method of obtaining glass. So the legend tells. What do you guys think? Is it possible to get glass in this way?
The spectators answer that it is unlikely that glass can be obtained in this way, since the temperature from an ordinary fire is insufficient for glass production.
Rabbit. That's right guys! But the Persians, as the Greek historian Herodotus tells, knew how to mine gold, silver, iron, and to dress the skins of animals. They adopted the art of dyeing fabrics from the Indians. The Hindus possessed significant chemical knowledge. The famous indigo blue paint served them for painting and for dyeing fabrics. They even printed designs on fabrics. And in Europe, this method was applied only in the XV century.
Even now the chemical knowledge of the Hindus is astonishing. Metallurgy was especially high. This is confirmed by the miracle of the metallurgical art of the ancients - the famous Kutub column near the city of Delhi. This column, 7 meters high, weighs over 6 tons. Accurate analyzes showed that it consists of chemically pure iron. And such iron does not rust at all. The researchers of the column did not find a trace of the influence of the atmosphere on it. There is an inscription on the column, according to which it can be established that it was placed in the 9th century. BC e. Almost 2800 years have passed since then. And during all this time not the slightest speck of rust has formed, and the conditions for rust in the damp and warm climate of India are very favorable. In modern production, only small quantities of chemically pure iron are obtained. How did the Indians make so much of the purest iron for the column? There are no seams on the column. How did they forge such a hulk? Even at present, such a mass of iron can only be forged in the largest factories with giant steam hammers. All this remains a complete mystery to us.
Guys, Winnie, Piglet, do you know who the alchemists are and what they did?
First, the audience from the audience tells the information they know, and then the characters - Rabbit, Winnie the Pooh and Piglet - supplement.
Piglet. Alchemists believed in materia prima - primary matter, which is everywhere and everywhere, but contaminated with various impurities. By removing impurities from primary matter, one can obtain a “quintessence”, a “philosopher's stone”, which turns base metals into noble ones (lead into silver, mercury into gold, etc.), heals all diseases, restores youth to old people and prolongs life beyond its natural limits.
Winnie the Pooh.Alchemists recognized the four elements of Aristotle - water, fire, air, earth - and considered their properties - dryness, moisture, warmth, cold. They believed that by combining these elements and qualities, all things in the world could be obtained. Consequently, alchemists considered it possible to detach from a substance its inherent properties and transfer these properties to other substances. Sometimes they attributed independent existence to properties.
Piglet. Alchemists were convinced that the sun, stars and planets affect all processes occurring on earth, in particular, that metals are born and develop in the bowels of the earth under the influence of heavenly bodies, like organic substances..
Rabbit.This mystical belief led them to believe that there were only seven metals on earth. The naive belief of the alchemists in this part is beautifully expressed by N.A. Morozov in a short poem:
"Seven metals created light,
According to the number of seven planets:
Gave us space for good
copper, iron, silver,
Gold, tin, lead...
My son! Sera is their father!
And hurry, my son, to find out:
Mercury is their mother to all of them!”
Winnie the Pooh. The time of domination of alchemical views is not only a time of delusions, disappointments and deceit. Despite the falsity of the basic idea of the alchemists, this era is characterized by a significant accumulation of knowledge in the field of chemistry and chemical technology. This development of events was facilitated by the main tendency of alchemists - to mix, heat, dissolve, distill, etc., everything that came to hand, in order to search for the philosopher's stone. Alchemists studied many reactions and obtained a large number of important compounds. They knew the properties of sulfuric, nitric and hydrochloric acids, saltpeter, gunpowder, aqua regia, alkalis, wine alcohol. Alchemists discovered phosphorus and a number of new metals (zinc, antimony, bismuth, cobalt, nickel) and introduced preparations based on them into medical practice.
Piglet. Millions of substances are known today. And what substances do you know, young chemists? Now we will test your knowledge. We offer you some puzzles.
"About two centuries ago
It was opened by accident.
Now I know him
and young
It is not a secret for you either.
Known to burn great
It contains sulfur, phosphorus, carbon,
Iron, magnesium. Vigorously
Hydrogen also burns.(Oxygen.)
"Get gases from the water,
Mix together - expect trouble.(Dangerous mix
from hydrogen and oxygen.)"Gas is garbage we don't need -
In the field it grew into food.(Carbon dioxide.)
"Reddish as a color,
Malleable, soft, like metal.
From acids, at the same time, he
Hydrogen was not released.
It can only oxidize
If we heat it in acid.
Right, you can guess
You're good enough now."“Separately, each is poisonous,
Together - wakes up the appetite.(Sodium chloride.)
“He went into the water and is clean and white,
I plunged - turned blue.(Copper(II) sulfate.)
"He is called lifeless,
But life without it is not created."Nicknamed disabled,
But strong in deed and in appearance."He will light up like a bright star,
White and light metal
In the thirteenth cell of the table
Took a place of honor.
For ease in alloys is given,
Created the power of the aircraft.
Tough and plastic, excellent
forged
This metal is silver.
In the composition of crimson rubies,
In sapphire blue lights
In gray ordinary clay,
In the form of emery stones.(Aluminum.)
“Only salt got into the water,
It became colder in the glass.”(Ammonium nitrate.)
Rabbit. What good fellows you guys are! How much do you know from the field of chemistry. But I have studied all kinds of literature on chemistry and have a little knowledge of the intricacies of a chemical experiment. Now I will try to invite the Magician Chemist to our holiday.
Under smooth music, making magical movements with his hands, the Rabbit conducts the chemical experiment "Volcano".
Experience "Volcano" on the table
Pour crystalline ammonium dichromate mixed with metallic magnesium into the crucible. Moisten the top of the mound with alcohol. Ignite the alcohol with a burning splinter.
The Wizard Chemist enters the scene.
Wizard chemist.Hello children! Hello, Rabbit, Winnie the Pooh, Piglet! I came to you to prove that chemistry is not just words, it is also a fairy tale.
A magical chemist performs a chemical experiment, imitating witchcraft.
Fireworks on the table experience
In a dry mortar, mix well equal volumes of powders of potassium permanganate, reduced iron and charcoal (you can take charcoal tablets). Pour the resulting mixture into an iron crucible, which is placed on a tripod and heated strongly with a burner flame. Soon a reaction occurs, and the ejection of reaction products in the form of sparks or fiery fireworks begins from the crucible. (In order to ensure fire safety, place a sheet of tin or asbestos under the tripod.)
Wizard Chemist. Guys, which of you can explain this phenomenon?
On a regular board
pouring water,
And a glass of melted snow
is also placed there.
I pour salt (ammonium nitrate) into a glass, and you, my friend (referring to Vinnie),
Feel free to mix.
(The magical chemist slowly counts to ten.)
Freeze a chemical glass,
Process?
(Audience responds, "Endothermic!")
Experience "Snake"
To demonstrate the "snakes" it is necessary to make blanks in advance. To do this, mix 10 g of potassium dichromate, 10 g of sugar and 5 g of sodium nitrate, ground into powder. Moisten the mixture slightly until the viscosity is reached, form into sticks with a diameter of 4-5 mm and a length of 8-9 cm, dry the sticks. Prepared "snakes" to strengthen in the sand and set on fire.
Wizard chemist.
I still can't do it
Snakes crawl out of the sand
Terrible, biting.
Are you crying out of fear?
Oriental music sounds, and a dance is performed in which girls dressed in oriental costumes depict snakes. The chemist-wizard is conducting an experiment at this time.
Experience "Chemical Chameleon"
In three flasks, pour 1/3 of the volume of a raspberry solution of potassium permanganate. Add a little dilute sulfuric acid to the first cylinder, water to the second, and a concentrated solution of potassium hydroxide to the third. The color of the solutions does not change. Add 5 ml of potassium sulfite solution to all cylinders and mix well with a glass rod. In the first cylinder, the solution instantly decolorizes, in the second, along with the discoloration, a brown flaky precipitate forms, and in the third, the crimson color turns into bright green.
Wizard chemist.
And now I offer you
The phenomenon is chemical.
But experience has a name
Purely biological.
Explain why
Name "Chameleon"
Given to him?
A magical chemist demonstrates the "Chemical Chameleon" experiment, after which the audience makes judgments.
Experience "Magic jug"
Place 10–20 mg of sodium hydrogen sulfate in the first glass, the same amount of sodium carbonate in the second, and a few drops of phenolphthalein solution in the third. The fourth and fifth glasses are for the effect of the experience. Pour 1 ml of water into each glass to dissolve the salts. A glass of sodium hydrosulfate should be noted unnoticed by the audience. Take a clean pitcher and pour water from the faucet into it. Next, pour all the water from the jug equally into all glasses. Then, only from four glasses, leaving, as if by chance, a glass with sodium hydrosulfate, pour "water" back into the jug. Then pour “water” out of the jug again into four glasses: it will already be painted crimson. Then pour the contents of all five glasses into a jug. After a short pause, pour the “water” from the jug into glasses, and it will again become colorless.
Wizard chemist.
From the magic jar
Water is pouring.
See how in the vessels
miracles happen.
The Wizard Chemist demonstrates the "Magic Jug" experience.
Experience "Hidden letter"
On a sheet of thick paper, you must first write the words “I want to become a chemist!”. Using a brush, soak the words “I want” and “chemist” with a dilute solution of copper sulfate, the word “become” -
dilute iron(III) chloride solution and dry. Fill a spray bottle with potassium hexacyanoferrate(II) solution. During the performance, the Wizard Chemist must process a sheet of paper with it. The text is shown to the audience: the words “I want” and “chemist” are written in red-brown color, and the word “become” is written in blue.
Wizard chemist.
By the will of Allah
I am on this paper
I can draw instantly
Magic portraits.
It only takes me to conjure
Whisper spells to Allah
And everyone can see
Your cherished desires.
The Wizard Chemist conducts the Hidden Letter experiment.
Experience "Blood without a wound"
For the experiment, 100 ml of iron(III) chloride with a mass fraction of 3% and 100 ml of potassium thiocyanate KSCN with a mass fraction of 3% are used. To demonstrate the experience, use a dull knife (you can use children's dishes). Call someone from the audience to the stage. With a cotton swab, his palm is washed with a solution of ferric chloride ("iodine"), and a knife is moistened with a colorless solution of potassium thiocyanate. Next, a knife is drawn across the palm of your hand: “blood” flows abundantly on the paper. "Blood" from the palm is washed off with cotton wool moistened with a solution of sodium fluoride.
Wizard chemist.
Here's another fun
(puts on a white coat).
Who will give a hand to cut off?
It's a pity the hand is cut off -
Then you need a patient
for treatment.
(Invites the audience to the stage.)
Operate without pain
True, there will be a lot of blood.
With every operation
Need sterilization.
Help Assistant
(referring to assistant)
Give me iodine.
Assistant. One moment!
Wizard chemist.
We moisten with iodine abundantly,
To keep everything sterile.
Don't move, patient!
Give me the knife, assistant!
(The magician chemist makes a “cut with a knife”, “blood” flows.)
Look, straight in a trickle
Blood flows, not water.
And now I'll dry my hand -
Not a trace of the cut!
The magic chemist shows the audience that there is no wound and the palm is completely clean.
Leading. Thank you dear wizard. You are truly a great magician. You proved to us that chemistry is a science that works wonders. And, like any science, chemistry requires the most responsible attitude towards itself. And only for the uninitiated, the miracles of chemistry seem like a miracle. I suggest you guys test your professional suitability. So, the first competition is “Who is faster?”.
Competition "Who is faster?"
The host invites two participants from among the audience to the stage. Using the periodic system of elements of D.I. Mendeleev, they must name five chemical elements in turn: one names the element, and the other must name the serial number of the named element as quickly as possible. With the help of a chess clock or a stopwatch, the time spent searching for the ordinal number of an element is taken into account. The winner is the participant who spent less time searching for the serial numbers of the five elements named by the opponent.
Leading. And now the competition "Who's next?".
Competition "Who's next?"
Two or three participants are invited to the stage. The player must walk as far as possible, naming a chemical element for each step. The game can be made more difficult by changing the list of names (any elements, only metals, only non-metals, elements of a certain period or group, etc.). The winner is the one who walks further without mistakes, hesitations and repetitions.
Leading. Well done boys! Now I suggest you complete the table.
A table is projected onto the screen through the projector:
| BUT | W | O | T |
|---|---|---|---|
Viewers are invited to fill in the empty cells of the table so that each column contains five chemical terms beginning with the specified letter. The winner is the one who writes all the words faster. At the end of the game, several students read out the words they invented, and the rest check whether these words are chemical terms. For example, in the first column you can write the following words: atom, anion, ammonia, argon, acetylene.
Leading. Great guys! You already know a lot about chemistry, and now I will try to guess your thoughts. I invite to the stage wishing to participate in the next number. I ask you to think of any chemical element on the periodic table. Now I ask you to double the number of the intended element. Add the number 5 to the resulting number. Multiply the resulting amount by 5. What number did you get? Name it.
The participant calls the number, and the host immediately announces the conceived playing element. The solution is as follows. Let element number 25 (manganese) be conceived. Let's carry out the corresponding mathematical operations with the number 25: 25 2 = 50; 50 + 5 = 55; 55 5 \u003d 275. The number 275 is reported to the leader, who discards the last digit in his mind, it turns out 27, then subtracts the number 2 from the received number, it turns out 25. This is the number of the intended element. After that, the leader can only name this element - manganese.
Leading.
What is there, what is there
No
On this white in the world.
Chemistry - difficult but important
subject,
All children study it.
Methane, ammonia and benzene -
does not matter
Secrets will be revealed one day.
We live interesting and fun
but
We all want to cheat
scary.
And you, friends, want
cheat?
The audience answers in the affirmative.
Leading. Yes, yes, of course, I had no doubts. But first, I want to ask my assistants to remind you of the safety rules.
Winnie the Pooh.
When working with substances
Don't pick them up
And don't taste it.
Reagents are not watermelon:
Peel off the skin from the tongue
And the hand falls off.
Rabbit.
Ask yourself a question
But don't stick your nose in a test tube.
You will cough and sneeze
Shed tears in hail.
Wave your hand to your nose -
Here is the answer to all questions.
Piglet.
With substances unknown
Don't mix
inappropriate:
Unfamiliar solutions you are a friend
do not merge with a friend,
Do not pour into one dish,
don't interfere, don't set fire.
Winnie the Pooh.
If you work
with a solid
Don't take it with a shovel
and don't you dare take it with a ladle.
You take it a little -
one eighth of a teaspoon.
When working with liquid
everyone should know:
It is necessary to measure in drops -
do not pour in a bucket.
Rabbit.
If acid is on your hand
or lye got in
Rinse your hand quickly with water
from the tap.
And to complication myself
do not deliver
Don't Forget the Teacher
notify.
Piglet.
Do not pour water into acid
vice versa -
Interfering carefully,
pouring in a thin stream
Pour acid into the water -
That's how you get out of trouble.
Winnie the Pooh.
Cleanliness is a man's friend.
Never forget about it.
And use clean dishes
On laboratory work
always!
Leading. We remembered the safety rules, now I suggest you solve a few riddles.
First riddle.
"I'm not afraid of acids,
Even very strong
But in alkali solutions
I become raspberry.
Brighter than the juice of all raspberries.
Who am I?"(Phenolphthalein.)
Second riddle.
"In alkalis I am very yellow,
And in acids - very red.
The indicator is very important!
What is my name?(Methyl orange.)
Third riddle.
"This yellow paper
Everything will indicate without difficulty.
It turns blue - there is alkali in the flask,
Turns red - acid.
Kohl neutral environment,
She won't change color.
What is her name?"(Universal.)
Guys, what are those substances called?
which were discussed in the riddles?(Indicators.)
Now it's time to invite the young experimenter to the stage. Who wants to cheat?
A person who wishes to conduct an experiment enters the stage.
Leading. The stand contains three numbered test tubes containing colorless liquids: water, acid solution and alkali solution. I ask you to investigate which of the test tubes contains water, acid and alkali?
An eighth-grader conducts an experiment to solve a qualitative problem for the recognition of substances.
Leading. Friends, what are you good fellows! You have already learned how to handle laboratory equipment and chemical glassware, conduct chemical experiments. And now the high school students will give you a quiz.
Chemical Quiz
1
. What chemical element brought many troubles to chemists from different countries?
(Answer: Many tragic events are associated with fluorine. Thomas Knox, one of the members of the Irish Academy of Sciences, died, another scientist of the same academy, George Knox, lost his ability to work, the famous chemist Jerome Nickles from Nancy was martyred. Brussels chemist P. Lyet paid with his life, poisoned French chemists J. Gay-Lussac and L. J. Tenard, English chemist G. Davy and many others suffered from fluorine and now work with fluorine requires great care and thoughtful protection measures. leads to severe inflammation of the respiratory tract and lungs, which often ends in pulmonary edema and death.The slightest carelessness in working with fluoride - and a person's teeth will be destroyed, nails will be damaged.)
2
. What element was first discovered in the sun? By whom and when was this discovery made?
(Answer. In 1868, during a solar eclipse, two astronomers - the Frenchman P.J. Jansen (in India) and the Englishman J.N. Suns, saw in the spectrum in addition to three familiar lines of hydrogen (red, green-blue and blue) a new one - bright yellow. Each reported the discovery to the Paris Academy of Sciences. In honor of this discovery, a gold medal was issued, decorated with portraits of Jansen, Lockyer and god The Sun of Apollo riding a chariot.
Lockyer proposed that the discovered substance be called the name of the Sun - helium. Only 27 years later, the English scientists W. Ramsay and W. Crooks managed to detect terrestrial helium in the mineral kleveite.)
3
. One of the chemists was a talented musician. He even wrote an opera. Who is this scientist and what did he create in science and music?
(Answer: Alexander Porfiryevich Borodin. He worked in the field of organic chemistry, left 91 published works on organic chemistry, including the study of aldols and the bromination of organic acids. He wrote the world-famous opera Prince Igor, a number of symphonic and chamber works.)
4
.Imagine a work on chemistry written not in prose, but in poetic form. Complex chemical conclusions ... in verse. What is the name of the chemist-poet.
(Answer. The ancient Greek philosopher Titus Lucretius Car, the poem "On the Nature of Things":
M.V. Lomonosov also wrote about chemistry in verse, for example, “Letter on the benefits of glass”:
| “They think wrong about things, |
Shuvalov, |
| Which glass is honored below |
minerals, |
| Beguiling beam |
shining in the eyes. |
| No less useful in it, |
there is no less beauty in it. |
| Not infrequently I am for that |
| descending from the Parnassus mountains; |
| And now from her to their top |
I'm coming back |
| I sing in front of you in delight |
praise, |
| Not expensive stones |
not gold, but glass. |
| And how I praise it |
I remember |
| Not the fragility of the deceitful |
I represent happiness. |
| Should not decay |
to be an example |
| What and strong fire |
can't destroy |
| Other earthly things |
final resolver: |
| Glass was born to him; fire it |
parent".) |
5.
“The fruit of his intensive pedagogical activity,” wrote D.I. Mendeleev, “is a lot of Russian chemists who gave him the nickname “grandfather of Russian chemists.” Which chemist are you talking about?
(Answer. A.A. Voskresensky. His research was of great importance for the development of chemistry and chemical industries. Thanks to his brilliant organizational skills, wide and fruitful pedagogical activity, favorable ground was prepared for the manifestation of the talents of outstanding Russian scientists - students of Voskresensky: D.I. Mendeleev, N.N. Beketova, N.A. Menshutkin, etc.)
6
. Which scientist's last name has nine letters, four of which are "o"? What is the role of this scientist in science?
(Answer. M.V. Lomonosov. He introduced the concept of molecules (corpuscles) and atoms (elements), introduced weighing, debunked the theory of phlogiston, substantiating the nature of combustion; developed a method for making colored glass, created modern Russian language, contributed to the development of physics , geology, geography, astronomy, metallurgy, etc.)
7
. Which chemical element and which chemist did the cat help to discover?
(Answer. In 1811, free iodine was obtained by the French chemist B. Courtois. It happened like this. Courtois prepared mixtures of substances in two different bottles. In one - sulfuric acid with iron, in the other - seaweed ash with alcohol. On a cat was sitting on the scientist's shoulder during the experiment. Suddenly, the cat jumped and knocked over the contents of the bottles. The liquids mixed, and clouds of purple vapor began to rise from them, forming crystals with a metallic sheen and a pungent odor as they settled. It was iodine.)
8
. The names of which chemical elements are associated with the color of simple substances or compounds?
(Answer. Chlorine is greenish, chromium is paint, rubidium is red, rhodium is pink, indium is blue, iodine is violet, cesium is blue, iridium is iridescent, phosphorus is light-bearing.)
9
. The names of what chemical elements are associated with the geography of their discovery?
(Answer. Scandium - the Scandinavian Peninsula, copper - the island of Cyprus, gallium - Gaul - the ancient Latin name of France, ruthenium - Russia, hafnium - the old name of Copenhagen, lutetium - the ancient name of Paris, polonium - Poland, France - France, americium - America, california is the state of california in the usa.)
10.
What chemical elements are named after scientists?
(Answer. Gadolinium - Y. Gadolin, curium - Pierre and Marie Curie, einsteinium - A. Einstein, fermium - E. Fermi, mendelevium - D.I. Mendeleev, lawrencium - E. Lawrence, rezerfor-
diy - E. Rutherford, nobelium - A.B. Nobel, borium - N. Bor, meitnerium - L. Meitner.)
11
. What element is called as a planet in the solar system?
(Answer. Uranus.)
12 . Which element according to ancient Greek mythology is "doomed" to eternal torment?
(Answer. Tantalum.)
13 . Which metal has wood in its name?
(Answer. Nickel.)
14 . The name of what noble metal is composed of marsh algae?
(Answer. Platinum.)
15 . A chemical element that adults and children like to play with at their leisure?
(Answer. Gold.)
Leading.Dear eighth graders! You have successfully completed all the tasks that we have offered you. And now the long-awaited moment has come. We light a "chemical fire", a fire without the use of matches or any incendiary devices, a fire that symbolizes that you have been awarded the honorary title of "Chemist". And the honor to light this fire is given to the winner of the Chemistry Olympiad(gives the name and surname of the Olympian).
The winner of the Olympiad conducts the experiment "Fire without matches".
Experience "Fire without matches"
In a clean, dry porcelain cup, prepare an oily mixture of finely ground potassium permanganate and concentrated sulfuric acid. Put a cup with the prepared mixture on the asbestos net, cover it with wooden chips. The Olympian takes a small piece of cotton wool soaked in alcohol and squeezes the alcohol over the chips so that its drops fall into a porcelain cup with a mixture of substances. After a click, a "chemical fire" ignites.
All participants of the holiday. Hooray! Hooray! Hooray!
Leading.
Our evening is entertaining
This is where we want to end.
And we wish everyone
Good luck in chemistry!
High school students give souvenirs to eighth graders and attach emblems with the title of "Chemist".
LITERATURE
Strempler G.I. Chemistry at your leisure. M.: Enlightenment, 1993;
Titova I.M., Ugryumov P.G. Guidelines for the use of chemical riddles in extracurricular work in chemistry. Leningrad: LGPI im. A.I. Herzen, 1989;
Kulikova E.L.. Evenings of entertaining chemistry. Minsk: Narodnaya Asveta, 1966;
Kukushkin Yu.N., Budanova V.F., Vlasova A.R., Krylov V.K., Panina N.S., Simanova S.A. What do we know about chemistry. Moscow: Higher school, 1993;
Somin L.E. Fascinating chemistry. M.: Education, 1978;
Gavruseyko N.P., Debaltovskaya V.I.. Chemical quiz. Minsk: Narodnaya Asveta, 1972; Parmenov K.Ya., Smorgonsky L.M.. Chemistry Reading Book. Moscow: State Educational and Pedagogical Publishing House of the Ministry of Education of the RSFSR, 1955;
Aleksinsky V.N.. Entertaining experiments in chemistry. M .: Education - JSC "Educational Literature", 1995.
Just two drops of glycerin - and potassium permanganate changes its color!
Complexity:
Danger:
Do this experiment at home
Why does the solution turn blue at first?
If you keep a close eye on the chameleon, you will notice that a few seconds after adding glycerin to the solution, it will turn blue. The blue color is formed by mixing violet (from MnO 4 - permanganate) and green (from MnO 4 2- manganate) solutions. However, it quickly turns green - the solution becomes less and less MnO 4 - and more MnO 4 2-.
Addition
The scientists were able to discover in what form manganese is able to color the solution blue. This happens when it forms the hypomanganate ion MnO 4 3- . Here, manganese is in the oxidation state +5 (Mn +5). However, MnO 4 3- is very unstable, and special conditions are needed to obtain it, so it will not be possible to see it in our experiment.
What happens to glycerin in our experience?
Glycerin interacts with potassium permanganate, giving it its electrons. Glycerol is taken in our reaction in great excess (about 10 times more than potassium permanganate KMnO 4). Glycerin itself, under the conditions of our reaction, turns into glyceraldehyde, and then into glyceric acid.
Addition
As we have already found out, glycerol C 3 H 5 (OH) 3 is oxidized by potassium permanganate. Glycerin is a very complex organic molecule, and therefore reactions involving it are often not simple. Oxidation of glycerol is a complex reaction during which many different substances are formed. Many of them exist for a very short time and turn into others, and some can be found in solution even after the end of the reaction. This situation is typical for all organic chemistry as a whole. Usually, those substances that are the most obtained as a result of a chemical reaction are called the main products, and the rest are called by-products.
In our case, the main product of the oxidation of glycerol with potassium permanganate is glyceric acid.
Why do we add calcium hydroxide Ca (OH) 2 to a KMnO 4 solution?
In an aqueous solution, calcium hydroxide Ca (OH) 2 decomposes into three charged particles (ions):
Ca (OH) 2 → Ca 2+ (solution) + 2OH -.
In transport, a store, a cafe or in a school class - everywhere we are surrounded by different people. And we behave differently in such places. Even if we do the same thing - for example, we read a book. Surrounded by different people, we do it a little differently: somewhere slower, somewhere faster, sometimes we remember what we read well, and other times we cannot even remember the lines the very next day. So potassium permanganate, surrounded by OH ions, behaves in a special way. It takes electrons from glycerin “more gently”, without hurrying anywhere. That is why we can observe the color change of the chameleon.
Addition
And what happens if you do not add a solution of Ca (OH) 2?
When an excess of OH - ions is present in a solution, such a solution is called alkaline (or they say that it has an alkaline reaction). If, on the contrary, there is an excess of H + ions in the solution, such a solution is called acidic. Why "on the contrary"? Because together the ions OH - and H + form a water molecule H 2 O. But if the ions H + and OH - are present equally (that is, we actually have water), the solution is called neutral.
In an acidic solution, the active oxidizing agent KMnO 4 becomes extremely ill-mannered, even rough. It very quickly takes electrons from glycerin (as many as 5 at a time!), And manganese turns from Mn ^ + 7 (in MnO 4 - permanganate) to Mn 2+:
MnO 4 - + 5e - → Mn 2+
The latter (Mn 2+) does not impart any color to the water. Therefore, in an acidic solution, potassium permanganate will very quickly discolor, and the chameleon will not work.
A similar situation will occur in the case of a neutral solution of potassium permanganate. Only we will not “lose” all the colors of the chameleon, as in an acidic solution, but only two - the green manganate MnO 4 2- will not be obtained, which means that the blue color will also disappear.
Can you make a chameleon using anything other than KMnO 4 ?
Can! The chromium (Cr) chameleon will have the following coloration:
orange (dichromate Cr 2 O 7 2-) → green (Cr 3+) → blue (Cr 2+).
Another chameleon - from vanadium (V):
yellow (VO 3+) → blue (VO 2+) → green (V 3+) → lilac (V 2+).
It's just that making solutions of chromium or vanadium compounds change their color as beautifully as it happens in the case of manganese (potassium permanganate) is much more difficult. In addition, you will have to constantly add new substances to the mixture. Therefore, a real chameleon - such that it will change its color "on its own" - is obtained only from potassium permanganate.
Addition
Manganese Mn, like chromium Cr and vanadium V, are transition metals - a large group of chemical elements with a whole range of interesting properties. One of the features of transition metals is the bright and varied color of compounds and their solutions.
For example, it is easy to obtain a chemical rainbow from solutions of transition metal compounds:
Every Hunter Wants to Know Where the Pheasant Sits:
Red (iron (III) thiocyanate Fe(SCN) 3), iron Fe;
Orange (Cr 2 O 7 2-bichromate), chromium Cr;
Yellow (VO 3+), vanadium V;
Green (nickel nitrate, Ni(NO 3) 2), nickel Ni;
Blue (copper sulfate, CuSO 4), copper Cu;
Blue (tetrachlorocobaltate, 2-), cobalt Co;
Violet (permanganate MnO 4 -), manganese Mn.
Development of the experiment
How to change the chameleon further?
Is it possible to reverse the reaction and get a purple solution again?
Some chemical reactions can proceed both in one direction and in the opposite direction. Such reactions are called reversible and, compared with the total number of chemical reactions, there are not so many known of them. It is possible to reverse the reaction by creating special conditions (for example, strong heating of the reaction mixture) or by adding some new reagent. Oxidation of glycerol with potassium permanganate KMnO 4 is not a reaction of this type. Moreover, within the framework of our experiment, it is impossible to reverse this reaction. Therefore, we will not be able to force the chameleon to change its color in the reverse order.
Addition
Let's see if there is a way to turn our chameleon?
First, a simple question: can oxidized glycerol (glyceric acid) convert manganese dioxide MnO 2 back to purple potassium permanganate KMnO 4 ? No, he can not. Even if we help him a lot (for example, heat the solution). And all because KMnO 4 is a strong oxidizing agent (we dealt with this a little higher), while glyceric acid has weak oxidizing properties. It is incredibly difficult for a weak oxidizing agent to oppose anything to a strong one!
Can MnO 2 be converted back to KMnO 4 using other reagents? Yes, you can. That's just for this you have to work in a real chemical laboratory! One of the laboratory methods for obtaining KMnO 4 is the interaction of MnO 2 with chlorine Cl 2 in the presence of an excess of potassium hydroxide KOH:
2MnO 2 + 3Cl 2 + 8KOH → 2KMnO 4 + 6KCl + 4 H 2 O
It is impossible to carry out such a reaction at home - it is both difficult (you will need special equipment) and unsafe. And she herself will have little in common with the bright and beautiful chameleon from our experience.
- PROJECT HYPOTHESIS
- Familiarize yourself with the information literature, conduct an analysis, draw conclusions
- Conduct practical studies of the influence of reaction conditions on the oxidizing-reducing properties of substances
- Find out the significance of one of these substances in everyday life in terms of OVR
- Purpose: REVEALING A SUBSTANCE THAT CAN CHANGE COLOR DEPENDING ON THE SITUATION, studying its properties and applications
- GET READ WITH INFORMATION SOURCES, LEARNING WHAT SUBSTANCES ARE CAPABLE OF COLOR CHANGE
- WE HAVE ANALYZED:
- REASONS FOR COLOR CHANGE
- DURING THE EXPERIMENT, THE INFLUENCE OF THE ENVIRONMENT ON THE COLORING OF KMnO4
- FOUND OUT THE VALUE OF POTASSIUM PERMANGANATE IN HOUSEHOLD AND ITS EFFECT ON PLANTS.
- Chemical chameleons are a number of substances that can change their color during chemical reactions.
- These include both organic and inorganic substances.
- the causes of the color of substances depend on a number of factors
- Molecule is painted
- free electrons
- odd number of electrons in a molecule
- chemical bond strength
- emerging chemical bond
- molecule color
- depends on the building
- substances themselves do not change color.
- Color change is a sign of a chemical reaction,
- more OVR
- Potassium permanganate (lat. Kalii permanganas)
- - potassium salt of permanganic acid
- The discoverer is the Swedish chemist and pharmacist Karl-Wilhelm Scheele.
- fused "black magnesia" - the mineral pyrolusite (natural manganese dioxide), with potash - potassium carbonate and saltpeter - potassium nitrate. This produced potassium permanganate, potassium nitrite and carbon dioxide:
- 2MnO2 + 3KNO3 + K2CO3 = 2KMnO4 + 3KNO2 + CO2
- MANGANESE
- (KMnO4).
- Dark purple crystals.
- It does not form crystalline hydrates.
- Solubility in water is moderate.
- Hydrolyzed
- Slowly decomposes in solution.
- Solutions are colored
- OXIDIZER
- in solution and during sintering.
- MANGANESE - THIS
- DECAYING
- EXPLOSIVE
- GIVES AN ALKALINE REACTION OF THE ENVIRONMENT
- changes
- coloring
- KMnO4
- Coloring
- depends
- from Wednesday
- solution
- neutral
- alkaline
- sour
- brown color
- green color
- colorless
- solution medium
- permanganate color
- Influence of the reaction of the medium on
- redox process
- Potassium permanganate forms various reduction products in various reactions of the medium
- KMnO4 is used as an oxidizing agent
- antioxidant
- APPLICATION
- APPLYING MANGANESE IN HOUSEHOLD, WE CARRY OUT OVR!
- OVR - PROCESS
- antiseptic
- has an emetic effect
- "cauterization" and "drying" of the skin and mucous membranes
- astringent action
- chemical burn
- poisoning
- Solid potassium permanganate and its strong
- solutions can be dangerous.
- Therefore, it should be stored in places inaccessible to babies, and handled with care.
- During the week, the earth and the diseased plant were watered with a weak solution. The white coating on the ground disappeared, the pests died. Potassium permanganate has disinfecting and antiseptic properties
- When watering once every two weeks with a weak solution, the appearance of the plants improved. Potassium permanganate contains elements that promote plant growth - manganese and potassium.
- Watering the plants with a weak solution constantly, it was found that plants of alkaline soils reacted positively, and acid soils reacted negatively. A solution of potassium permanganate has an alkaline environment
- Treatment with a concentrated solution causes burns and even death of the plant.
- PROJECT HYPOTHESIS
- substances "Chameleons" exist
- CONCLUSION:
- SUBSTANCES THEMSELVES COLOR CHANGE
- CAN NOT.
- THE HYPOTHESIS IS NOT CONFIRMED
- 1C Tutor. Chemistry. CD - disc.
- Big Encyclopedia. Cyril and Methodius, 2005 CD-ROM.
- Kuzmenko N.E., Eremin V.V., Popkov V.A. Beginnings of chemistry. A modern course for applicants to universities.
- In 2 volumes - M. 1997. BDE Biology, M. "Drofa" 2004
- Ecology. Cognitive Encyclopedia, M. Bustard
- Stepin B.D., Alikberova L.Yu. Chemistry book for home reading. - M., Chemistry, 1994.
- Shulpin G.B. This fascinating chemistry. – M.; Chemistry, 1984.
- INFORMATION SOURCES
- orange dark black-green
- purple black gray
- It is known that double and single bonds can relatively easily change places with each other. But each interatomic bond is a pair of electrons common to the atoms they bind. So it turns out that in the conjugation section, the binding electrons can move quite freely within this section. Such freedom entails important optical consequences.
- Another curious fact: compounds with an odd number of electrons in the molecule are more often colored than compounds with an even number of electrons. Let's say the C(C6H5)3 radical has an intense brown-violet color, while C(C6H5)4 is colorless. Nitrogen dioxide NO2 with an odd number of electrons in the molecule is brown-brown, and when it dimerizes, a colorless compound N2O4 is obtained (doubling the number of electrons became even). The reason here is that in systems with an odd number of electrons, one of them is unpaired and is able to move relatively freely within the entire molecule. And, as mentioned earlier, this can cause coloring to appear.
- a compound made up of almost colorless constituent parts,
- turns out to be colored. So, the Fe3 + ion is colorless, the Fe (CN) 64 - ion, which is part of the yellow blood salt, is slightly colored yellow. But Fe43, which is obtained by draining solutions containing these ions, has an intense blue color.
- The reason for the appearance of color should be sought in the fact that a compound with stronger chemical bonds is formed here (not with ionic, but with covalent bonds); the degree of mutual sharing of electrons becomes so significant that there is also a strong shift of the absorption maximum to the visible region of the spectrum and an increase in the absorption intensity.
- iodine solvates in water are brown-red, and in carbon tetrachloride - violet
- Silica gel impregnated with cobalt chloride turns blue in dry air and pink in wet air. And the thing is that with an excess of moisture, the molecules of blue cobalt chloride CoCl2 form a complex compound with water molecules - crystalline CoCl2 6H2O, which has a dark pink color.
- It is reduced to manganese compounds of different oxidation states.
- in an acidic environment: 2KMnO4+ 5K2SO3 + 3H2SO4 =
- 6K2SO4+ 2MnSO4+ 3H2O
- in a neutral environment: 2 KMnO4+ 3K2SO3 + H2O = 3K2SO4 + 2 MnO2+ 2KOH
- in alkaline environment: 2 KMnO4+ K2SO3 + KOH=
- K2SO4 + 2 K2MnO4+ H2O,
- KMnO4 + K2SO3 + KOH = K2SO4 + K2MnO4 + H2O (cold)
- DECAYING with the release of oxygen
- 2KMnO4 →(t) K2MnO4 + MnO2+ O2
- EXPLOSIVE
- 2KMnO4 + 2H2SO4 → 2KHSO4 + Mn2O7 + H2O,
- Reacts with typical reducing agents
- (ethanol, hydrogen, etc.).
- It is necessary to add a KMnO4 solution to the water prepared for bathing, but in no case potassium permanganate crystals - otherwise a chemical burn is possible.
- In case of poisoning with a concentrated solution of this substance, a burn of the mouth, esophagus and stomach occurs (wash the stomach with warm water with the addition of activated charcoal)
- You can also use a solution containing in two liters of water half a glass of a weak solution of hydrogen peroxide and one glass of table vinegar. In this case, permanganate ions turn into less dangerous manganese(II) cations:
- 2KMnO4 + 5H2O2 + 6CH3COOH =
- 2Mn(CH3COO)2 + 5O2 + 2CH3COOK + 8H2O
- USEFUL TIPS
