Transcript

1 MBOU “Lyceum 9 named after A.S. Pushkin ZMR RT” Scientific research work “Natural indicators” Completed by: Chelyukanova Karina Vladimirovna, 8th grade student Scientific supervisor: Chugunova S.A., chemistry teacher of the highest qualification category 2014

2 Contents Introduction page History of the discovery of indicators page Natural indicators page Experimental part 3.1. Selection of materials for the preparation of indicators page Results of testing plant indicators page Results of tests with an indicator from plant raw materials (black currant) page Conclusions page References page 9

3 INTRODUCTION Experience is the only right way to ask nature and hear the answer in her laboratory. D.I.Mendeleev. The purpose of this work is to study the possibility of obtaining substances that are acid-base indicators from plant materials and using them to determine the pH of some solutions used in everyday life. The object of study is plant fruit extracts as putative indicators. Research objectives: 1. To get acquainted with the history of the production and use of indicators. 2. Collect indicator plants. 3. Prepare extracts from plant material. 4. Test natural indicators with solutions of acids and bases. 5. Experimentally prove the possibility of using plant fruit extracts as chemical indicators. 1. History of the discovery of indicators Pigments and coloring substances isolated from plants were known back in Ancient Egypt and Ancient Rome. As for the beginning of the use of organic substances as indicators, it dates back to the 17th century. and is associated with the name of the famous English physicist and chemist Robert Boyle (). In the laboratory of R. Boyle, litmus paper was first made based on this solution. After some thought, R. Boyle called such substances indicators, which translated from Latin meant “pointers.”

4 2. Natural indicators Indicators (from the Latin indicator indicator) are complex organic substances that change color depending on whether they are in an acidic, alkaline or neutral environment. The most common indicators are litmus, phenolphthalein and methyl orange (methyl orange). If there are no real chemical indicators, then home-made indicators from natural raw materials can be successfully used to determine the solution environment. Natural indicators contain colored substances that can change their color in response to a particular influence. And when they find themselves in an acidic or alkaline environment, they visually signal this. 3. EXPERIMENTAL PART 3.1. Selection of materials for the preparation of indicators One of the most important stages of my research is the choice of raw materials for the preparation of the indicator, with which I studied solutions: water (neutral medium), soda (alkaline medium), acetic acid (acidic medium), blackcurrant juice, cherries (berries), strawberries (berries), carrots (juice), beets (juice), hibiscus (red tea), turmeric, red currants (berries). Testing indicators with universal indicator paper I prepared blackcurrant juice, turmeric powder solution, hibiscus tea infusion, beet juice, strawberry juice and divided them into 2 test tubes. I added vinegar to one (acidic environment), and added a soda solution to the other (alkaline environment). Solutions were examined with universal indicator paper.

5 Conclusions: all juices and infusions that are red in color are bright red in an acidic environment, from light green to dark green in an alkaline environment. Exception: beets, which are yellow in an alkaline environment. 3.2. Results of testing indicator plants I decided to use black currant juice as an indicator. I added a few drops of blackcurrant juice to all test tubes with test indicator plants. Raw materials for Natural Color solution preparation color indicator in acidic in indicator solution (universal) medium pH > 7 (add vinegar) alkaline medium pH< 7 (добавим соду) сока черной смородин ы Вишня (ягоды) Темно-красный Ярко- Грязно- Темно- ph=1 красный зеленый красный Клубника Розовый Оранжевы Светло- Красный (ягоды) ph=2 й коричневы й Морковь Светло- Желтый Светло- Ярко- (плоды) оранжевый зеленый красный ph=4-5 Свекла (плоды) Рубиновый Ярко- Желтый Темно-

6 ph=0 red red Hibiscus (red tea) Black currant (berries) Dark red ph=1 Burgundy ph=0 Red Dirty greenred Dark Red Green _ Turmeric Orange Light Dirty Dark (powder) ph=3 orange green orange Red currant (berries) Bright red ph=2 Pink Green Dark red Conclusion: when blackcurrant juice is added to juices, infusions, the color of the indicator varies from dark orange to dark red Test results of the indicator from plant raw materials (black currant) I prepared solutions from substances used in everyday life, and studied using universal indicator paper (pH 0 12) with a standard scale. It was found that the pH of these solutions varies in the range pH 1 11; Moreover, only three out of ten solutions showed an acidic reaction. As a raw material for preparing the indicator solution, I took frozen blue-violet black currant berries (Ribesnigrum).

7 When examining frozen blackcurrant juice (dark red), the color change was evident both in an acidic environment (to bright red) and in an alkaline environment (to bright blue). A few drops of the prepared indicator solution were added to the test tube with the test solution. The results are presented in the table. Solutions ph Toothpaste 8 Soda 10 Vinegar 3 Milk 6 Table salt 7 Ammonia 11 Soap 9 Solutions Toothpaste Soda Vinegar Milk Table salt Ammonia Soap Blackcurrant juice Dirty blue Blue Pink Light burgundy Hot pink Blue Light pink As a result Based on the work carried out, an acid-base indicator was obtained from plant raw materials (black currant). It was used to determine the pH of solutions used in everyday life. Experimental

8, it was proven that the accuracy of determining the pH of the medium using an indicator from black currant is comparable to the accuracy of a universal indicator. In all solutions, the results of testing with a blackcurrant indicator coincided with the results of testing with a universal indicator. Thus, we have proven that blackcurrant berry extract can be used as an acid-base indicator. 4.CONCLUSIONS 1.Plant pigments can be used as indicators. These indicators are quite sensitive, especially the brightly colored juices of black currants, cranberries, viburnums, blueberries and beets, cherries, and hibiscus (red tea). The properties of these indicators are comparable to those of universal indicator paper. 2. Blackcurrant juice changes its color to pink in an acidic environment, and blue in an alkaline environment. 3. Solutions of plant indicators can be used as acid-base indicators to determine the environment of solutions in a school chemistry laboratory. Ease of preparation and safety make such indicators easily accessible, and therefore good assistants in working with acids and bases. 4. The color intensity of the indicators depends on the concentration of the solutions being tested, which allows an approximate assessment of the aggressiveness of the environment. 5. Plant indicators can be used in everyday life. Beetroot juice changes its ruby ​​color to bright red in an acidic environment, and yellow in an alkaline environment. Knowing the properties of beet juice, you can make the color of borscht bright. To do this, add a little table vinegar or citric acid to the borscht.

9 6. Natural indicators can be used to determine the composition of drugs used for treatment. Many drugs are acids, salts and bases. By studying their properties, you can protect yourself. For example, aspirin (acetylsalicylic acid), many vitamins cannot be taken on an empty stomach, since the acids in their composition will damage the gastric mucosa. 7. Natural indicators can be used to determine the acidity of the soil, since on the same soil, depending on its acidity, one type of plant can produce a high yield, while others will be depressed. 5. References 1. Pilipenko A.T. "Handbook of Elementary Chemistry". Kyiv "Naukova Duma". 1973 Page Information from 1september.ru. 3. Children's encyclopedia. M. Academy of Pedagogical Sciences. RSFSR. 1966 Page Information from the website alchemic.ru “Good advice”. 5. Leenson I.A. "Entertaining chemistry." Moscow. 1996 Page Baykova V.M. "Chemistry after school." 1976 Page Scientific and practical magazine “Chemistry for schoolchildren” Page Educational and methodological newspaper for chemistry teachers “First of September”, 22, 2007

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Introduction

In our lives, we encounter various substances that surround us. This year we started studying an interesting subject - chemistry. How many substances are there in the world? What are they? Why do we need them and what benefits do they bring?

In class, while studying the topic “The most important classes of inorganic compounds,” I became acquainted with the indicators - litmus, phenolphthalein and methyl orange. What are indicators? Indicators are substances that change their color depending on the solution environment. Using indicators, you can determine the solution environment.

I decided to find out as much as possible about these amazing substances, and whether it is possible to use the natural materials that we have at home as indicators.

Relevance of the topic: Today, the properties of plants and the possibilities of their use in chemistry, biology and medicine are of great interest.

Goal of the work: explore natural indicators and how we can use them in everyday life.

To achieve the goal, the following tasks were set:

Study material about indicators as chemical substances.

Study natural indicators.

Find out how you can apply knowledge about natural indicators in everyday life.

To achieve my goals, I studied the literature in the library and chemistry classroom, used materials from Internet sites, and also used methods of observation, experiment, comparison, and analysis.

My work consists of three chapters. In the first chapter, I looked at the variety of indicators and their chemical nature. In the second, what plants are indicators and their role in nature and human life. In the third chapter is my practical research.

1.Chemical indicators

1.1 History of the discovery of indicators

Indicators (from the Latin Indicator - pointer) are substances that allow you to monitor the composition of the environment or the progress of a chemical reaction. Today, a large number of different indicators, both chemical and natural, are known in chemistry. Chemical indicators include acid-base, universal, redox, adsorption, fluorescent, complexometric and others.

The pigments of many plants can change color depending on the acidity of the cell sap. Therefore, pigments are indicators that can be used to study the acidity of other solutions. The general name for such plant pigments is flavonoids. This group includes the so-called anthocyanins, which have good indicator properties.

The most used plant acid-base indicator in chemistry is litmus. It was already known in Ancient Egypt and Ancient Rome, where it was used as a violet paint substitute for expensive purple. The use of pigments to determine the environment of a solution was first scientifically applied by Robert Boyle (1627 - 1691). The year was 1663, as usual, the laboratory was in full swing with intense work: candles were burning, various substances were heated in retorts. The gardener entered Boyle's office and placed a basket of magnificent dark purple violets in the corner. At this time, Boyle was going to conduct an experiment to produce sulfuric acid. Admired by the beauty and aroma of violets, the scientist, taking a bouquet with him, headed to the laboratory. His laboratory assistant, William, told Boyle that two bottles of hydrochloric acid had arrived yesterday from Amsterdam. Boyle wanted to look at this acid, and to help William pour the acid, he put violets on the table. Then he took the bouquet from the table and went to the office. Here Boyle noticed that the violets were slightly smoking from the splashes of acid that had fallen on them. To rinse the flowers, Boyle placed them in a glass of water. After a while, he glanced at the glass with violets, and a miracle happened: the dark purple violets turned red. Naturally, Boyle, as a true scientist, could not ignore such an incident and began research. He discovered that other acids also turn violet petals red. The scientist thought that if he prepared an infusion from the petals and added a little to the solution being tested, he could find out whether it was sour or not. Boyle began preparing infusions from medicinal herbs, tree bark, and plant roots. However, the most interesting was the purple infusion obtained from a certain lichen. Acids changed its color to red, and alkalis changed its color to blue. Boyle ordered the paper to be soaked in this infusion and then dried. This is how the first litmus test was created, which is now available in any chemical laboratory. Thus, one of the first substances was discovered, which Boyle even then called indicators.

1.2. Types of indicators

The Chemical Encyclopedic Dictionary distinguishes among indicators: adsorption, isotopic, acid-base, redox, complexometric, luminescent indicators.

My work is devoted to acid-base indicators. With the development of chemistry, the number of acid-base indicators increased. Indicators obtained as a result of chemical synthesis: phenolphthalein, introduced into science in 1871 by the German chemist A. Bayer, and methyl orange, discovered in 1877.

Nowadays, several hundred artificially synthesized acid-base indicators are known. We can meet some of them in the school chemistry laboratory. Phenolphthalein - in chemistry - an indicator, expressed as colorless crystals without taste or smell. Melting point - 259-263°C. In medicine - a laxative (outdated name - purgen). In an alkaline environment it turns bright crimson, and in a neutral and acidic environment it is colorless. Litmus (lacmoid) is an indicator extracted from some lichens, and turns red when exposed to acids, and blue when exposed to alkalis. Methyl orange is an acid-base indicator, a synthetic organic dye from the group of azo dyes. It appears pink in acids and yellow in alkalis. Depending on the acidity of the environment, the brilliant green dye also changes color (its alcohol solution is used as a disinfectant - “brilliant green”). In order to check this, you need to prepare a diluted solution of brilliant green: pour a few milliliters of water into a test tube and add one or two drops of the pharmaceutical preparation. The solution acquires a beautiful green-blue color. In a strongly acidic environment, its color changes to yellow, and an alkaline solution becomes discolored.

Table of some chemical indicators:

Indicator	pH interval	Color change
Thymol blue		Red - yellow
Methyl orange		Red - orange-yellow
Methyl red		Red - yellow
		Red - blue
Thymol blue		Yellow - blue
Phenolphthalein		Colorless - red
Thymolphthalein		Colorless - blue

The table shows acid-base indicators common in laboratory practice in increasing order of pH values ​​that cause color changes. The first color corresponds to the pH values ​​before the interval, the second color corresponds to the pH values ​​after the interval.

However, most often in laboratory practice a universal indicator is used - a mixture of several acid-base indicators. It allows you to easily determine not only the nature of the environment (acidic, neutral, alkaline), but also the acidity value (pH) of the solution.

2. Indicators in nature

2.1.Anthocyanins and carotenoids

Nature is a unique creation of the Universe. This world is beautiful, mysterious and complex. The plant kingdom amazes with its variety of colors. The color palette is varied and is determined by the chemical composition of the cellular contents of each plant, which includes pigments - bioflavonoids. Pigments are organic compounds present in plant cells and tissues that color them. Pigments are located in chromoplasts. More than 150 types of pigments are known. Bioflavonoids include, for example, anthocyanins and carotenoids.

Anthocyanins are widely distributed coloring substances in the plant world. Anthocyanins (from the Greek words for “flower” and “blue”) are natural coloring substances. Anthocyanins give plants colors ranging from pink to dark purple.

The structure of anthocyanins was established in 1913 by the German biochemist R. Willstetter. The first chemical synthesis was carried out in 1928 by the English chemist R. Robinson. They are most often dissolved in cell sap, sometimes found in the form of small crystals. Anthocyanins are easily extracted from any blue or red part of the plant. If, for example, you boil chopped beet roots or red cabbage leaves in a small amount of water, the anthocyanin will soon turn purple.

The presence of anthocyanins in the cell sap of plants gives the flowers of bells a blue color, violets - purple, forget-me-nots - sky blue, tulips, peonies, roses, dahlias - red, and flowers of carnations, phlox, gladioli - pink. Why is this dye so many-sided? The fact is that anthocyanin, depending on the environment in which it is located (acidic, neutral or alkaline), is able to quickly change its hue. Anthocyanins have good indicator properties: in a neutral environment they acquire a purple color, in an acidic environment - red, in an alkaline environment - green-yellow. Unfortunately, almost all natural indicators have a serious drawback: their decoctions deteriorate quite quickly - they turn sour or mold (see Appendix 1). Another drawback is that the color change range is too wide. In this case, it is difficult or impossible to distinguish, for example, a neutral medium from a weakly acidic one or a weakly alkaline from a strongly alkaline one.

Plants with high concentrations of anthocyanins are popular in landscape design.

Carotenoids (from the Latin word “carrot”) are natural pigments from yellow to red-orange, synthesized by higher plants, fungi, sponges, and corals. Carotenoids are polyunsaturated compounds, in most cases containing 40 carbon atoms per molecule. These substances are unstable in light, when heated, and when exposed to acids and alkalis. Carotenoids can be isolated from plant materials by extraction with organic solvents.

Natural dyes are found in flowers, fruits, and rhizomes of plants.

2.2 Indicative geobotany

Ancient folk beliefs often spoke of herbs and trees capable of revealing various treasures. There are many books dedicated to geological flowers. In “Ural Tales” P.P. Bazhov writes about magical flowers and “gap-grass” that open storehouses of copper, iron, and gold to people. In recent years, scientific connections have been made between certain plants and certain mineral deposits. Tricolor field violets, pansies or horsetail tell a person that the soil, albeit in minimal quantities, contains zinc and gold. Pink bindweed and golden coltsfoot grow in entire glades on clay and calcareous soils. Often, by the ugly development of some plants, you can recognize the presence of many minerals in the soil. For example, on soils with a normal boron content, plants such as wormwood, prutnyak, and solyanka grow tall, and on soils with a high content of this element, these plants become dwarf. The changed shape of poppy petals indicates that there are deposits of lead and zinc underground.

It will help you find water and determine whether it is fresh or salty. Licorice is a large plant with dark greenery and red-violet clusters of flowers. If the plant blooms magnificently, the water is fresh; if it blooms weakly and a light coating appears on the leaves, the water is salty.

Sometimes plants accumulate so many valuable elements that they themselves become “ore.” The very rare metal beryllium is accumulated in lingonberry berries, larch bark, and Amur adonis. It turned out that ordinary quinoa contains a lot of lead, and sage contains germanium and bismuth. Wormwood turned out to be the best scout. Above the ore zones it contains a lot of mercury, lead, zinc, silver, antimony, and arsenic. The accumulation of ore elements and heavy metals does not go unnoticed for the plant; its appearance changes. Boron inhibits plant growth and causes branching. Plants do not bloom, roots die. Excess beryllium changes the shape of branches in young pines. If the soil is high in iron, plants have bright green foliage and appear strong and healthy. And with the arrival of autumn, they are the first to turn yellow and lose their leaves. High concentrations of manganese in the soil discolor leaves.

This means that by studying the chemical composition of plants, new deposits can be discovered. And now the geobotanical method is still used in practice. Even a science has emerged - “indicative geobotany”, which studies plants that are sensitive to environmental changes and help to discover the riches of the earth’s interior.

3. Practical part: study of natural indicators

I decided to find out which of the edible plants available at home could be used as acid-base indicators. For the experiment, I took frozen blueberries, strawberries, cherries, raspberries, and beet roots.

To conduct the experiments, I used the following materials and equipment: glasses, funnels, test tubes, mortars and pestles, a knife, filter paper, water, ethyl alcohol, solutions of sodium hydroxide and hydrochloric acid.

I ground the berries in a mortar and crushed the beets using a grater. Extraction of pigment (paint) from crushed raw materials was carried out in two ways: using alcohol and water (see Appendix 2).

Colored alcoholic and aqueous solutions were filtered using a paper filter and gauze to rid the infusion of plant particles. The entire chemical experiment was carried out in the school chemistry classroom together with the work leader.

Experiment 1. Study of the change in color of prepared solutions depending on the environment.

Solutions of alkali and acid were poured into test tubes and solutions of natural indicators were added. A change in the color of the solutions was noted (see Appendix 3).

Research results.

Scale of color transitions of infusions of some plants in different environments.

Plants	Acidic environment pH< 7	Neutral environment pH = 7	Alkaline environment pH> 7
			Blue-green
		Burgundy
	Dark red	Light red (scarlet)
Strawberry

Experiment 2. Study of the environment of household chemical solutions.

Using natural prepared indicators, I examined the environment of the shampoo I use at home, baby soap, cleansing milk, and dishwashing detergent (see Appendix 4).

Research results.

As a result of the research, I concluded that shampoo and facial wash are quite suitable for use. But dishwashing detergent is alkaline and can affect the skin of your hands, because... our skin has a slightly acidic reaction.

Experience3. Heating the beetroot solution to a boil.

The beet water solution was heated to a boil and the color changed from deep red to pale red. When hydrochloric acid was added, the color returned and even became more pronounced. This happens when cooking borscht. To return a beautiful rich color, you can add a little malic or acetic acid.

Conclusion

This work turned out to be very interesting and useful. Makes you want to learn and get more information about the use of plants. As a result, it has been proven that many plants contain anthocyanins, due to which they can be natural indicators. They can be used both in everyday life and in chemistry for research. I also learned that when entering the human body with fruits and vegetables, anthocyanins exhibit an effect similar to vitamin P; they maintain normal blood pressure and blood vessels, preventing internal hemorrhages. Anthocyanins are required by brain cells and improve memory. They are powerful antioxidants that are 50 times stronger than vitamin C. Many studies have confirmed the benefits of anthocyanins for vision. The highest concentration of anthocyanins is found in blueberries. Therefore, preparations containing blueberries are most in demand in medicine.

The surface of our skin has a slightly acidic environment, which protects it from bacteria and, having studied the environment of solutions of substances for personal hygiene, I came to the conclusion that frequent use of soap, especially by teenagers, has an adverse effect on the skin. Washing powder and dishwashing detergent also affect the skin of the hands since they have an alkaline environment.

So, I came to the conclusion:

The color of leaves, fruits, and flowers of plants is determined by the presence of pigments belonging to the anthocyanin group. Anthocyanins are found in cell sap and are highly soluble in water.

Representatives of the studied plants (cherries, raspberries, beets, strawberries, blueberries) can be used as indicators.

Plant indicators are available, safe to use, and economical.

It was not in vain that I worked on this topic, since my small discoveries will benefit not only me, but also other students.

In summer you can pick flowers and berries in the garden and forest. These can be irises, pansies, tulips, raspberries, cherries, etc. Dry the collected petals and fruits for future use (the fruits can be frozen), and you can safely use them as indicators.

Bibliography

IN AND. Artamonov Green Oracles. - Publishing house "Thought", 1989.

L.A. Savina I'm exploring the world. Children's encyclopedia. Chemistry. - M.: AST, 1996.

B.D. Stepin, L.Yu. Alikberova Entertaining tasks and spectacular experiments in chemistry. - M.: Bustard, 2002.

G.I. Strempler. Home laboratory. (Chemistry at leisure). - M., Education, Educational literature. - 1996.

Encyclopedic dictionary of a young chemist. - M.: Pedagogy, 1982.

Internet resources

6.1 www.alhimik.ru

6.2 http://xumuktutor.ru/e-journal/2011/10/16/robert_boyle/

6.3http://www.inflora.ru/cosmetics/cosmetics258.html

Applications

Photographic report of the research carried out.

Annex 1.

Photo of an alcohol and water solution on the eighth day after preparation.

Appendix 2.

Photo of the process of preparing solutions of natural indicators.

Appendix 3.

Photo of the experiment “Study of the change in color of prepared solutions depending on the medium (alkaline, acidic).

Appendix 4.

Photo of the experiment “Study of the environment of household chemical solutions ».

1.Dishwashing liquid

2.Cleansing foam

3. Shampoo

4. Washing powder

5. Laundry soap

Karachaevo-Circassian Republic

MCOU "Secondary School a. Maly Zelenchuk named after Hero of the Soviet Union

Umar Khabekova"

Khabez municipal district

Research

in chemistry on the topic:

“Indicators at our home.”

Work completed:

Kalmykova Sataney

8th grade student

Supervisor:

chemistry teacher of the highest qualification category

Okhtova Elena Ramazanovna

2015

Content

Introduction………………………………………………………………………………..……3

Theoretical part.

1 .1.Natural dyes……………………………………................................4

1 .2.The concept of indicators……………………………………………………..6

1.3. Classification of school indicators and methods of their use..7

1.4. Hydrogen index……………………………………………………..8

Practical part.

2.1.Obtaining natural indicators……………………………………...9

2.2. Study of the solution environment with plant indicators………….10

1. 1. Chemical experiments with food…………………………….10

1. 1. Chemical experiments with detergents……………………...…11

Conclusions…………………………………………………………………………………...13

Conclusion………………………………………………………………………………….13

References……………………………………………………………....14

Introduction

In nature, we encounter various substances that surround us. This year we began to get acquainted with an interesting subject - chemistry. How many substances are there in the world? What are they? Why do we need them and what benefits do they bring? We were interested in such substances as indicators.

In chemistry lessons, the teacher told us about indicators: indicators such as litmus, phenolphthalein and methyl orange.

Indicators (from English indicate-indicate) are substances that change their color depending on the solution environment. Using indicators, you can determine the solution environment.

We decided to find out whether it is possible to use the natural materials that we have at home as indicators.

Relevance and novelty The theme is that “as a result of scientific and technological progress uncontrolled by society on the planet in general, and in Russia in particular, the environmental situation is deteriorating from year to year, both in cities and in rural areas. Food additives - dyes, thousands of medicines made from new polymers that are qualitatively different from natural ones - are appearing on sale. The food industry based on the technology of deep chemical processing of natural products, as well as the production of genetically modified cereals, vegetables and fruits, has become widespread. As a result of this, we are already living in a largely artificial, “toxic” ecosystem (atmosphere, hydrosphere, lithosphere, biosphere). This ecosystem is significantly different for the worse from the one in which our ancestors lived.”

Goal of the work:

Learn the concept of indicators;

Familiarize yourself with their opening and functions;

Learn to identify indicators from natural objects;

Investigate the effect of natural indicators in various environments;

Research methods :

Study of popular science literature;

Obtaining indicator solutions and working with them.

Hypothesis: Can plants or vegetables of a given area serve as bioindicators of acidity as environmentally safe for human health?

Tasks:

prepare solutions of indicators that would indicate the presence of an acid or base;

Check the acidity of soap, tea and food.

Subject of study: grape juice, beets, tea, detergents and food.

I . Theoretical Part.

1.1. Natural dyes.

People obtained their first paints from flowers, leaves, stems and roots of plants. For a long time, Russian peasants used vegetable dyes; they dyed wool and linen fabrics in various colors. To obtain paint, crushed plant parts were usually boiled in water and the resulting solution was evaporated to a thick or solid precipitate. The fabrics were then boiled in a dye solution, adding soda and vinegar to make the color last longer.

The main component of paint is the dye.Dye - This is a coloring chemical compound that gives a material a certain color.

The use of natural dyes was known as early as 3000 BC. In earlier times, organic dyes were extracted exclusively from animal and plant organisms. For example, a violet-blue dye was isolated from the leaves of the tropical indigofera plant growing in India.indigo . From the leaves of the genus Lawsonia (henna) of the family Merlinaceae are still isolatedhnu- red-orange dye, green henna is obtained from dried and mashed viburnum leaves, which are widely used to strengthen and color hair. The Chinese have been using dye to color silk, paper, wood and food products since ancient times.curcumin, contained in the rhizomes and stems of plants of the genus turmeric (curry). In Russia, onion peels, leaf bark, birch brooms, and dream grass (snowdrop) have long been used to dye fabrics and eggs for Easter; marigold flowers, juniper berries and other dyes extracted from plants growing in our climatic conditions.

The color of paints is primarily determined by the pigments they contain (from the Latin “pigmentum” - paint). Pigments are different: natural and synthetic, organic and inorganic, chromatic (from the Greek “croma” - “color”) and achromatic. Achromatic pigments determine white and black colors, as well as the entire gray color range lying between them.

Pigments , in biology, colored substances in the tissues of organisms that participate in their life activities. Determine the color of organisms; in plants they participate in photosynthesis (chlorophylls, carotenoids), in animals - in tissue respiration (hemoglobins), in visual processes (visual purple), protect the body from the harmful effects of ultraviolet rays (in plants - carotenoids, flavonoids, in animals - mainly melanins ). Some pigments are used in the food industry and medicine.

Pigments (from Latin pigmentum - paint), in chemistry - colored chemical compounds used in the form of fine powders for dyeing plastics, rubber, chemical fibers, and making paints. They are divided into organic and inorganic. Of the organic ones, the most important are azo pigments, phthalocyanine and polycyclic pigments. Pigments also include organic varnishes.

Inorganic pigments are divided into natural and artificial (soot, ultramarine, white, etc.).Mineral paints (natural), natural pigments (ochre, yellow lead, cinnabar, mumiyo, chalk, lapis lazuli, etc.) used for coloring materials.

Vegetable dyes do not last as long as aniline dyes, so they are not used in industry. Dyes are used not only for dyeing fabrics, but also for preparing drinks, creams, and caramel. Many vegetables owe their color to pigments - carotenoids. Numerous representatives of the carotene family differ from each other in the composition and structure of their molecules, which affects their color shades, but they all have one common property - solubility in fats.

With the development of chemistry, natural dyes began to be replaced by synthetic ones. Nowadays, there are more than 15,000 dyes of various shades belonging to different classes of compounds.

1.2. The concept of 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 and methyl orange.

The very first acid-base indicator, litmus, appeared. Litmus is an aqueous infusion of 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 conduct an 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 put them in a glass of water. And - what miracles - violets, their dark purple petals, turned red. Boyle became interested and conducted experiments with solutions, each time adding violets 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 and what substances are contained in the solution. The best results were obtained from experiments with litmus lichen. Boyle dipped ordinary paper strips into an infusion of litmus lichen. I waited until they were soaked in the infusion, and then dried them. Robert Boyle called these tricky pieces of paper indicators, which translated from Latin means “pointer”, since they point to the solution environment. It was the indicators that helped the scientist discover a new acid - phosphoric acid, which he obtained by burning phosphorus and dissolving the resulting white product in water.

If there are no real chemical indicators, you can successfully use... home, wild and garden flowers and even the juice of many berries - cherries, chokeberries, currants - to determine the acidity of the environment. Pink, crimson or red geranium flowers, peony or colored pea petals will turn blue when placed 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 dyes -anthocyanins. It is anthocyanins that give various shades of pink, red, blue and purple to many flowers and fruits.

Beet coloring matterbetaine or betanidin in soup In a dry environment it becomes discolored, and in an acidic environment it turns red. That's why borscht with sauerkraut has such an appetizing color.

1.3. Classification of school indicators and methods of their use.

Indicators have different classifications. Some of the most common are 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 them can be found in a school chemistry laboratory.

Phenolphthalein (sold in a pharmacy under the name "purgen") - white or white with a slightly yellowish tint, finely crystalline powder. Soluble in 95% alcohol, practically insoluble in water. Colorless phenolphthalein is colorless in acidic and neutral environments, but turns crimson in an alkaline environment. Therefore, phenolphthalein is used to determine the alkaline environment.

Methyl orange - orange crystalline powder. Moderately soluble in water, easily 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 solution being tested.

Another method of application is to use strips of paper soaked in an indicator solution or indicator mixture and dried at room temperature. Such strips are produced in a wide variety of options - with or without a color scale applied to them - a color standard.

1.4. Hydrogen index.

The universal paper indicator has a scale for determining the medium (pH).

pH value,pH– a value characterizing the concentration of hydrogen ions in solutions. This concept was introduced in Danish chemist . The indicator is called pH, after the first letters of Latin wordspotentia hydrogeni - the strength of hydrogen, orpondus hydrogenii - weight of hydrogen. Aqueous solutions can have a valuepHin the range 0-14. In pure water and neutral solutionspH=7, in acidic solutionspH<7 и в щелочных pH>7. QuantitiespHmeasured using acid-base indicators.

Table No. 1

Indicator color in different environments.

Indicator name

Indicator color in different environments

in sour

in neutral

in alkaline

Methyl orange

Red

(pH < 3,1)

Orange

(3,1 < pH < 4,4)

Yellow

(pH > 4.4)

Phenolphthalein

Colorless

( pH< 8,0)

Colorless

(8,0 < pH < 9,8)

Crimson

( pH >9,8)

Litmus

Red

( pH< 5)

Violet

(5 < pH < 8 )

Blue

( pH > 8)

The pH value is the most important characteristic of biological fluids; blood, lymph, saliva, gastric, intestinal and cellular juice. Therefore, it is often determined during clinical tests, assessing human health.

DesignationpHwidely used in chemistry, biology, medicine, agronomy, ecology and other areas of life. It is no coincidence that there is so much talk about it in the media, and even people far from chemistry are keenly interested in this concept. Television screens show how thepHin a person’s mouth after brushing his teeth with such and such a paste or after chewing such and such gum... An absolutely neutral environment corresponds to the valuepH, equal to exactly 7. The more acidic the solution, the lesspH, and in the presence of alkalipHbecomes more than 7.

II . Practical part.

2.1. Obtaining natural indicators.

To obtain natural indicators, we proceeded as follows. The material under study was grated and then boiled, as this leads to the destruction of cell membranes, and anthocyanins freely leave the cells, coloring the water. The solutions were poured into transparent containers. To find out which decoction serves as an indicator for a particular environment and how its color changes, it was necessary to conduct a test. We took a few drops of a homemade indicator with a pipette and added them alternately to an acidic or alkaline solution. Table vinegar served as the acidic solution, and baking soda solution served as the alkaline solution. If, for example, you add a bright red decoction of beets to them, then under the influence of vinegar it will turn red, soda - red-violet, and in water - pale pink, because The medium in water is neutral.

The results of all these experiments were carefully recorded in table No. 2; We present a sample of it here.

Table No. 2

Indicator

Solution color

original

in an acidic environment

in an alkaline environment

Grape juice

Dark red

Red

Green

Red beets

Red

Bright red

Red - purple

Purple onion

Light purple

Pink

Light green

Red cabbage

Violet

Red

Light green

Grape juice

Red

Red

Light green

Also, regular tea can be used at home as an indicator. We noticed that tea with lemon is much lighter than without lemon. In an acidic environment it becomes discolored, and in an alkaline environment it becomes darker.

tea neutral environment tea in acidic and alkaline environment

2.2. Study of the solution environment with plant indicators.

First, it was necessary to repeat the safety rules when working with chemicals and equipment.

2.2.1. Chemical experiments with food.

We decided to use a natural indicator - beet broth - to check the acidity of milk 2.5% and sour cream 20%. A few drops of beet broth were added to the milk. The solution turned pale pink. This means that the environment in milk is closer to neutral. The same experiment was repeated with sour cream. The color of the sour cream after adding the natural indicator was deep pink. This is closer to a slightly acidic environment. The conclusion is this: milk has a neutral environment, and sour cream has an acidic environment. Grape juice gave interesting results. In an alkaline environment the juice turned blue, in an acidic environment it turned red, in a neutral environment it turned pink. Next, we added grape juice to milk and sour cream. In milk it turned light green, and in sour cream it turned pale pink. This means that sour cream has a slightly acidic environment.

Table No. 3

Product under study

Beet color

Wednesday

Milk 2.5%

Pale pink

Neutral

Sour cream 20%

Pink

Slightly sour

2.2.2. Chemical experiments with detergents.

Next, we decided to test the environment in soap and laundry detergent. To do this, we examined Tide powder and soap.DOVE"and laundry soap. First, we prepared solutions of these detergents. An indicator, beet broth, was added to each solution. In laundry soap the indicator turned purple, and in soap "DOVE- pink. This means that laundry soap has a highly alkaline environment, and soap “DOVE"has a neutral environment. A very high alkali content in soap causes great harm to the skin of the hands. “Laundry soap” contains a high alkali content, while soap “DOVE» lowest alkali content (neutral environment). From this we can conclude: in soap "DOVE» the lowest alkali content, therefore, it is safer for the skin of the hands. Our indicator was added to the Tide powder solution. The solution turned purple, and after a few minutes it became colorless. This means that the powder solution is highly alkaline. This way you can check the acidity of any detergent.

Table No. 4

Changes in indicator color in detergents

Test solution

Color

Wednesday

Tide powder

violet

alkaline

Laundry soap

violet

alkaline

Soap "DOVE»

pink

neutral

Any work must result in practical value. During the experiments, somehow the proposal came naturally to dye the eggs with our natural dyes. An egg mashed with beet juice turns burgundy. Onion peel is brown. Prepared indicators cannot be stored for a long time; they are destroyed in water. You can prolong their effect by soaking filter paper in the extract and then drying it. Such papers should be stored in closed packaging.

Conclusions.

Studying the indicators, we came to the following conclusions:

Acid-base indicators are necessary in chemical analysis to determine the environment of solutions.

There are natural plants that exhibit the properties of acid-base indicators.

Brightly colored beets, tea and grape juice can be used as natural indicators.

Solutions of natural indicators can be prepared and used at home.

Natural indicators are also quite “accurate” determinants of the acidity of liquids, like the most “professional” indicators: litmus, phenolphthalein and methyl orange.

Plant dyes in an acidic environment give shades of red, in an alkaline environment - violet, and in a neutral environment - pink.

Conclusion.

In conclusion, I want to say that I learnedidentify the solution environment, showing the effect of soap solutions on the skin of the hands, synthetic detergents on fabrics when washing clothes.

The result of this work (research) was the development of my creative thinking and practical activities, the formation of interest in understanding chemical phenomena and their patterns.

In the end, I want to express my attitude towards chemistry in the words of M. Gorky: “First of all and most carefully, study chemistry. This is an amazing science, you know... Its keen, bold gaze penetrates into the fiery mass of the sun and into the darkness of the earth’s crust, into the invisible particles of your heart, and into the secrets of the structure of a stone, and into the silent life of a tree. She looks everywhere and, discovering harmony everywhere, persistently seeks the beginning of life..."

Bibliography

1. Alekseeva A. A.. Medicinal plants. / A. A. Alekseeva Ulan-Ude: Buryat. book publishing house, 1974.- 178 p.

2. Alikberova L. Yu. Entertaining chemistry / L. Yu. Alikberova M.: AST-PRESS, 1999. - 560 p.

3 . Janis V.K. 200 experiments / V.K. Janice M.: AST-PRESS, 1995. - 252 p.

4 . Kuznetsova N. E. Chemistry. Textbook for grade 10 / N.E. Kuznetsova M: Ventana-Graf, 2005.- 156 p.

5. Nikolaev N.G. Local history / N.G. Nikolaev, E.V. Ishkova M.: Uchpedgiz, 1961.- 164 p.

6 . Novikov V.S. School atlas - guide to higher plants / V.S. Novikov, I.A. Gubanov M: Education, 1991. – 353 p.

7. Savina L. A. I explore the world. Children's Encyclopedia Chemistry / L.Ya. Savina M: AST, 1997.- 356 p.

8. Sinadsky Yu.V. Healing herbs / Yu.V. Sinadsky, V.A. Sinadskaya M: Pedagogy, M. 1991.- 287 p.

9 . Somin L.E. Fascinating chemistry / L.E. Somin M.: Pedagogy, 1978.- 383 p.

The values ​​in parentheses are taken from the book “A Chemist’s Quick Reference Guide,” comp. V.I. Perelman, M.-L., “Chemistry”, 1964.

1. The exact pH transition value for most indicators depends somewhat onionic strengthsolution (I). Thus, the pH value of the transition, determined at I = 0.1 (for example, a solutionchloridessodium or potassium) differs from the transition point in a solution with I=0.5 or I=0.0025 by 0.15...0.25 pH units.
2. *Column “x” - the nature of the indicator: k-acid, o-base.
3. Phenolphthaleinin a strongly alkaline environment it becomes discolored. In concentrated sulfuric acid, it also gives a red color due to the structure of the phenolphthalein cation, although not as intense. These little-known facts can lead to errors in determining the reaction of the environment.

   Study of natural decoctions Coloring of natural indicators

   Indicators in an acidic environment (Fig. 1) in an acidic environment (Fig. 2)

   Study of solutions Coloring of natural indicators

   indicators in an alkaline environment (Fig. 3) in an alkaline environment (Fig. 4)

   Decoction of rose petals and cloves in an acidic and alkaline environment (Fig. 5-6)

   Decoction of sea buckthorn berries and cherries in an acidic and alkaline environment (Fig. 7 - 8)

   A decoction of blackberries and blueberries in an acidic and alkaline environment (Fig. 9 - 10)

   A decoction of red onions and cranberries in an acidic and alkaline environment (Fig. 11-12)

   A decoction of beets and strawberries in an acidic and alkaline environment (Fig. 13-14)

   A decoction of black currants and raspberries in an acidic and alkaline environment (Fig. 15-16)

   Decoction of red cabbage leaves in an acidic and alkaline environment (Fig. 17)

   APPENDIX 4

   Research results Research results

   indicator from beets (Fig. 1) indicator from juice and decoction

   Strawberries (pic 2)

   Colors of blackcurrant decoction and juice (Fig. 3) Colors of cherry decoction and juice in an acidic environment (Fig. 4)

   Colors of decoction, juice of fresh and frozen red cabbage in an alkaline and acidic environment (Figure 5, 6)

   Coloring juices in acid (Figure 7)

   Coloring juices in alkali (Figure 8)

   APPENDIX 5

   Study of the color of an indicator from a decoction of red cabbage, rose petals and carnations in solutions with different pH values ​​(Fig. 1-3)

   Study of the color of an indicator from a decoction of cherries, blueberries and red onions in solutions with different pH values ​​(Fig. 4-6)

   Study of the color of an indicator from a decoction of beets and black currants in solutions with different pH values ​​(Fig. 7, 8)

   APPENDIX 6

   Research on dishwashing detergent (Fig. 1-2)

   Stain remover research (Fig. 3).

   Studying the properties of glass cleaner (Fig. 4)

   Investigation of the environment of the rust remover (Fig. 5)

   Study of the Progress detergent environment (Fig. 6)

   Purpose of the work: To study the properties of synthetic indicators used in the school laboratory and obtained from individual juices and decoctions of flowers, vegetables, berries, to study the nature of the environment with their help.

   Hypothesis: solutions of plant indicators can be prepared independently and used in a chemical laboratory and at home if it is necessary to determine the solution environment, the properties of indicator solutions depend on the method of preparation, solutions of natural indicators will help determine the pH value of a solution with the accuracy of a universal indicator.

   study literary sources on the topic; prepare solutions of indicators from natural raw materials in different ways and study the influence of acidic and alkaline environments on their colors; compare the obtained data with the properties of the acid-base environment indicators of the factory universal indicator; determine the solution environment of some household products; Research objectives

   Object of study: natural plants whose pigments have indicator properties, synthetic indicators in a school laboratory. Subject of research: acid-base properties of decoction and juice of berries, vegetables, flowers Research methods: Experiment Observation Comparison Analysis of the results obtained

   Classification of indicators

   Experiment No. 1 “Obtaining solutions of synthetic indicators and studying their properties”

   Phenolphthalein Methyl Orange Lakmoid

   Experiment No. 2 “Obtaining plant indicators”

   Experiment No. 3 “Study of the color of the obtained plant indicators in acidic and alkaline environments”

   Acidic environment

   Alkaline environment

   Red cabbage

   Experiment No. 4 “Comparison of the effects of indicators obtained from decoction and freshly squeezed juices of fresh and frozen berries and vegetables”

   Experiment No. 4 “Comparison of the effects of indicators obtained from decoction and freshly squeezed juices of fresh and frozen berries and vegetables” Table beets Strawberries Red onions Raspberries Red cabbage Blackberries

   Experiment No. 5 “Study of changes in the color of indicators at different pH values ​​of the medium in comparison with the properties of a universal indicator”

   Red cabbage

   Experiment No. 6 “Detection of the properties of solutions of substances used in everyday life”

   Experiment No. 6 “Detection of the properties of solutions of substances used in everyday life”

   Conclusions from the work: Solutions of plant indicators can be prepared at home and used as acid-base indicators to determine the environment of solutions. The most suitable plants for obtaining indicators are beets, red roses, cloves, black currants, red cabbage, blackberries, blueberries, and cherries. The properties of these indicators are comparable to those of universal indicator paper.

   It is better to prepare indicators from plant raw materials in the form of juice solutions. Frozen raw materials can also be used. A noticeable difference in the colors of some juices of frozen and fresh berries requires further study using examples of other berries in the summer. Conclusions from the work:

   Synthetic indicators change the original shade obtained by adding acid or alkali less than natural indicators. The resulting indicators can be used in chemistry lessons, in elective courses, so that students have an idea of ​​natural indicators and use them in their lives in the future, since synthetic indicators are not available to everyone. Work with natural indicators can be continued by studying the indicator properties of other plants. Conclusions from the work:

   Thank you for your attention!

Municipal budgetary educational institution

"Secondary school No. 22"

With. Knevichi Artemovsky urban district

Project work

Indicators around us

Completed by: Kozlova Ksenia

student of 8th grade "A"

Head: Klyots Elena Pavlovna

teacher of chemistry and biology

Artem, 2018

Content

Introduction - - - - - - - - - - 3

1. Literature review. - - - - - - - 4

1.1. History of indicator opening - - - - - - 4

1.2. Indicators in nature - - - - - - - 5

1.3. Indicators in chemistry lessons - - - - - 6

2. Materials and methods - - - - - - - - 8

2.1. Experiment in the school laboratory - - - - - 8

2.2. Processing results - - - - - - 9

Conclusions - - - - - - - - - - 10

Conclusion - - - - - - - - - 10

References - - - - - - - 11

Introduction

Indicators are widely used in chemistry, including in school. Any schoolchild will tell you what phenolphthalein, litmus or methyl orange are.

An indicator is a device, device, substance that displays changes in any parameter of a controlled process or the state of an object. When one or another indicator is added to an acidic or alkaline environment, the solutions change color. Therefore, indicators are used to determine the reaction of the environment (acidic, alkaline or neutral). We were also told that the juices of brightly colored berries, fruits and flowers have the properties of acid-base indicators, since they also change their color when the acidity of the environment changes.

I was interested in the question: what plant juices can be used as indicators? Is it possible to prepare solutions of plant indicators yourself? Are homemade indicators suitable for use at home, for example to determine the environment of food?

Relevance of the topic: attracting the interest of schoolchildren to popularize organic chemistry through simple and safe experiments.

Goal of the work : Obtain natural indicators from surrounding natural materials. Study their properties using the example of their use as indicators.

Tasks:

Study the literature on indicators;

Familiarize yourself with their opening and functions;

Learn to identify indicators from natural objects;

Investigate the effect of natural indicators in various environments.

1. Literature review

1.1 History of the discovery of indicators

Substances that change color depending on the environment were first discovered in the 17th century by the English chemist and physicist Robert Boyle. He conducted thousands of experiments. Here's one of them.

Candles were burning in the laboratory, something was boiling in the retorts, when the gardener came in at the wrong time. He brought a basket of violets. Boyle loved flowers very much, but the experiment had to begin. He took several flowers, smelled them and put them on the table. The experiment began, they opened the flask, and caustic steam poured out of it. When the experiment ended, Boyle accidentally looked at the flowers; they were smoking. To save the flowers, he put them in a glass of water. And - what miracles - the violets, their dark purple petals, turned red. The scientist ordered his assistant to prepare solutions, and dropped a flower into each. In some glasses, the flowers immediately began to turn red. Finally, the scientist realized that the color of violets depends on what substances are contained in the solution [1 ].

Boyle began preparing infusions from other plants: medicinal herbs, tree bark, plant roots, etc. However, the most interesting was the purple infusion obtained from litmus lichen. Acids changed its color to red, and alkalis to blue.

Boyle ordered the paper to be soaked in this infusion and then dried. This is how the first litmus paper was created, which is available in any chemical laboratory. Thus, one of the first substances was discovered, which Boyle even then called “indicator."

Robert Boyle prepared an aqueous solution of litmus lichen for his experiments. The bottle in which he kept the infusion was needed for hydrochloric acid. After pouring out the infusion, Boyle filled the flask with acid and was surprised to find that the acid turned red. Interested in this phenomenon, Boyle added a few drops to an aqueous solution of sodium hydroxide as a test and discovered that litmus turns blue in an alkaline medium. Thus, the first indicator for detecting acids and alkalis was discovered, named litmus after the lichen. Since then, this indicator has been one of the indispensable indicators in various studies in the field of chemistry [2 ].

1.2 Indicators in nature

The plant kingdom amazes with its variety of colors. The color palette is varied and is determined by the chemical composition of the cellular contents of each plant, which includes pigments. Pigments are organic compounds present in plant cells and tissues that color them. Pigments are located in chromoplasts. More than 150 types of pigments are known.

If there are no real chemical indicators, you can successfully use... home, wild and garden flowers and even the juice of many berries - cherries, chokeberries, currants - to determine the acidity of the environment. Pink, crimson or redgeranium flowers, petalspeonyorcolored peaswill turn blue if placed in an alkaline solution. Juice will also turn blue in an alkaline environment.cherriesorcurrants. On the contrary, in acid the same “reagents” will take on a pink-red color. Plant acid-base indicators here are colorants namedanthocyanins . Exactlyanthocyanins impart various shades of pink, red, blue and purple to many flowers and fruits.

Beet coloring matterbetaine in an alkaline environment it becomes discolored, and in an acidic environment it turns red. That's why borscht with sauerkraut has such an appetizing color.

Plants with high concentrations of anthocyanins are popular in landscape design.

Carotenoids (from the Latin word “carrot”) are natural pigments from yellow to red-orange, synthesized by higher plants, fungi, sponges, and corals. Carotenoids are polyunsaturated compounds, in most cases containing 40 carbon atoms per molecule. These substances are unstable in light, when heated, and when exposed to acids and alkalis. Carotenoids can be isolated from plant materials by extraction with organic solvents.

Natural dyes are found in flowers, fruits, and rhizomes of plants.

Unfortunately, almost all natural indicators have a serious drawback: their decoctions deteriorate quite quickly - they turn sour or mold. Another drawback is that the color change interval is too wide. In this case, it is difficult or impossible to distinguish, for example, a neutral environment from a slightly acidic or slightly alkaline one.

1.3 Indicators in chemistry lessons

Indicators - means "pointers". These are substances that change color depending on whether they are in an acidic, alkaline or neutral environment. The most common indicatorslitmus, phenolphthalein and methyl orange.

Phenolphthalein (sold in a pharmacy under the name "purgen") - white or white with a slightly yellowish tint, finely crystalline powder. Soluble in 95% alcohol, practically insoluble in water. Colorless phenolphthalein is colorless in acidic and neutral environments, but turns crimson in an alkaline environment. Therefore, phenolphthalein is used to determine the alkaline environment.

Methyl orange - orange crystalline powder. Moderately soluble in water, easily soluble in hot water, practically insoluble in organic solvents. The color of the solution changes from red to yellow.

Litmus - black powder. Soluble in water, 95% alcohol, acetone, glacial acetic acid. Transition of solution color from red to blue.

Less common indicators can also be used in laboratory conditions: methyl violet, methyl red, thymolphthalein. Most indicators are used only in a narrow pH range, but there are also universal indicators that do not lose their properties at any value of the hydrogen index[ ].

2. Materials and methods

2.1 Experiment in the school laboratory

For research work I usedred onions and their peels, cherries, cranberries, beets and cauliflower.

For preparing plant indicatorsa small amount ofraw materialseach sampleIcrushedin a mortar, transferred to a test tubeflooded12 ml of water and boiled for 1-2 minutes. The resulting decoctions were cooled and filtered(Fig. 1).

Having thus obtained the indicator solutions, I checked what color they had in different environments.

To obtain a solution with an acidic environment, citric acid was used, and with an alkaline solution, baking soda was used.

The prepared solutions were checked for the acidity of the medium using a universal indicator, comparing their indicators with those of hydrochloric acid and alkali solution (Fig. 2).

I poured these solutions into test tubes for further experiment. For convenience, I divided the test tubes by color: those with pink markings are a soda solution, and those with yellow markings are a citric acid solution. By usingpipetteAndI added to the solutions according toa few drops of homemade indicator.

2.2 Processing of results

The results of these experimentspresentedin tablese.

Table 1. Results

Raw materials for preparing the indicator

Natural indicator color

Coloring in an acidic environment

Alkaline painting

Red onion peel

red

red

brown-green

Red onion

colorless

light pink

light yellow

Beet

bright red

bright red

Dark red

Cauliflower

colorless

light pink

colorless

Cranberry

bright red

bright red

Navy blue

Cherry

Dark red

bright red

violet

The best result was obtained with a decoction of cranberries, cherries, and red onion peels (Fig. 3)

conclusions

Obtained natural indicators from surrounding natural materials;

We studied their properties using the example of their use as indicators;

We studied the literature on indicators;

Conclusion

After conducting research work, I came to the following conclusions:

many natural plants have indicator properties that can change their color depending on the environment in which they find themselves;

The following natural raw materials can be used to produce solutions of plant indicators: berriescherries, cranberries, cauliflower, beets, red onions and their peels;

homemade indicators from natural raw materials can be used in chemistry lessons in rural schools if there is a problem in providing the school with chemical indicators.

This research needs to be continued in the summer when there are many flowering plants. Brightly colored flowers contain many different pigments that can be indicators and used as dyes.

Bibliography

1. Vetchinsky K.M. Plant indicator. M.: Education, 2002. – 256 p.

2. Vronsky V.A. Plant indicator. - St. Petersburg: Parity, 2002. – 253 p.

3. Stepin B. D., Alikberova L. Yu. Entertaining tasks and spectacular experiments in chemistry. – M.: Bustard, 2002

4. Shtrempler G.I. Home laboratory. (Chemistry at leisure). - M., Education, Educational literature.-1996.

5. http://www.alhimik.ru/teleclass/glava5/gl-5-5.shtml

6. fb.ru/article/276377/chto -takoe -indikator -v -himii -opredelenie -primeryi- printsip -deystviya