Interesting experiments with starch. How to conduct a visual experiment with iodine with a child

Starch, potatoes and iodine are suitable not only for jelly and sauces. If desired, with the help of various experiments, you can entertain an inquisitive baby at home or in kindergarten for the whole evening.

Costs - a minimum, pleasure and development - a maximum. Try to repeat something from the list below, and you will no longer see kissels - everything will go to tricks.

Starch, we'll find you! Experience with iodine.

What do you need? Starch, iodine, pipette, any food products.

Starch is a white powdery substance that can be found in the kitchen of almost every housewife. In addition, it is found in many products that we use daily. And the usual tincture of iodine will help determine its location. For the experiment, take starch, bread, cheese, lemon, cookies, potatoes.

First, dissolve a spoonful of starch in a glass of water and drop iodine into it - the liquid will turn blue.

Explain to the child that if a drop of iodine meets starch, it will change its color to blue. Now, using a pipette, drop iodine on a small piece of bread, cheese, other prepared samples and observe what happens.

Iodine will change its color on bread, biscuits, potatoes. But on cheese and lemon - no. There are fruits and vegetables in which the starch content depends on the degree of their ripeness and variety. So, for example, you can determine more starch in a green banana than in a ripe one, and in sour apples it will be much more than in sweet ones.

Non-Newtonian fluid - an experiment from starch and water

What do you need? 1 cup cornstarch, half cup water.

As we know, a non-Newtonian fluid is a substance that changes its viscosity depending on the speed of impact on it. These changes are very interesting to watch.

Getting a non-Newtonian liquid at home is very simple, just mix water and starch in the right proportion. To immediately feel how the changes are happening, move starch with water with your hands. From the very beginning, you will understand that this is not so easy to do.

Then pick up a little of the resulting mixture and try to mold something from it, mash it - it will behave like plasticine. But it is worth stopping for a couple of seconds, as the mixture turns into a liquid and flows from your hands. However, if you start sculpting again, you will feel that the material becomes harder again.

It is interesting to try to pour the liquid - if the cup with the mixture is turned over sharply, then it will not pour out, but if slowly, the substance will drain. You can invite your child to play with small toys. They can easily "run" on the surface of matter, but if they stop, they will drown like in a swamp. If the child tries to slap the mixture with his palm, the surface will be hard, and if he simply puts a pen on it, it will sink into the liquid.

Starch is dancing

What do you need? Non-Newtonian fluid, dye, subwoofer.

For this experiment, you will have to get a subwoofer, but it's worth it. Color the starch mixture and place in a shallow pan. Put the tray on the subwoofer and turn on the music (the frequency should be 40-60 Hz). Hold the tray with your hands. Before your eyes, the mixture will begin to bounce and break away from the surface, bending. An extraordinary spectacle.

The experiment with a non-Newtonian fluid on children's holiday e.g. at a birthday party. Children will receive a lot of positive emotions and unforgettable impressions, and most importantly, they will be able to become participants in amazing experiments.

"Lizun" from starch

What do you need? A glass of starch, half a glass of water, 100 grams of PVA glue, a couple of drops of gouache, a plastic bag.

Mix water, starch and dye, pour in glue and stir with a stick or spoon. Pour the mass into a bag and knead until a dense, viscous and viscous substance is obtained. By the way, playing with it develops fine motor skills.

Summary: Experiments with iodine and starch. Entertaining chemistry at home. Entertaining chemistry for children. Entertaining chemistry experiments. Fascinating chemistry. Entertaining experiments in chemistry.

After doing this experiment, you will see how clear liquid turns dark blue in an instant. To conduct the experiment, you may need to go to the pharmacy for the necessary ingredients, but the miracle transformation is worth it.

You will need:

3 liquid containers
- 1 tablet (1000 mg) of vitamin C (sold in a pharmacy)
- alcohol solution of iodine 5% (sold in a pharmacy)
- hydrogen peroxide 3% (sold in a pharmacy)
- starch
- measuring spoons
- measuring cups

Work plan:

1. Thoroughly crush 1000 mg of vitamin C with a spoon or mortar in a cup, turning the tablet into a powder. Add 60 ml warm water, stir thoroughly for at least 30 seconds. We will conditionally call the resulting liquid Solution A.

2. Now pour 1 teaspoon (5 ml) of Solution A into another container, and also add: 60 ml of warm water and 5 ml of iodine alcohol solution. Note that brown iodine will become colorless when reacted with vitamin C. We will call the resulting liquid Solution B. By the way, we will no longer need Solution A, you can put it aside.

3. In a third cup, mix 60 ml of warm water, half a teaspoon (2.5 ml) of starch and one tablespoon (15 ml) of hydrogen peroxide. This will be Solution C.

4. All preparations are now complete. You can call the audience and put on a show! Pour all Solution B into the cup containing Solution C. Pour the resulting liquid several times from one cup to another and back again. A little patience and ... after a while, the liquid will turn from colorless to dark blue.

Experience Explanation:

You can explain to a preschooler the essence of the experience in a language accessible to him as follows: iodine, reacting with starch, stains it in Blue colour. Vitamin C, on the other hand, tries to keep iodine colorless. In the struggle between starch and vitamin C, in the end, starch wins, and the liquid turns dark blue after a while.

We continue to conduct experiments for children. Last time we talked about, and today we present to your attention experiments for children with iodine.

Surely you remember from the school biology course how potatoes turned blue when a diluted iodine solution was dripped onto it. Something similar, but in a more entertaining form, we will do today. So, in today's article, experiments for children:

- in search of starch,

- intensive coloring,

- cover up traces

- drawing on milk.

Experience for children "In search of starch"

In the first photo you can see what we need for today's experiments:

• 5% iodine
• Pipette
• Starch
• Disposable cups
• 10% ascorbic acid solution

But for the first experience, we still need a plate of food. I didn't include it in common list, since the products in which you will look for starch with a crumb can be very diverse. We took flour, wheat groats, cereals, slice of bread, fresh cucumber, lemon, radish.

Now let's prepare a solution of iodine. To do this, pour water into a glass and drip a few drops of iodine with a pipette, stir well. You can quite trust your baby to work with a pipette. So your experiments will develop not only the curiosity of the baby to know the world around him, but also.

Why make a solution if you can drip ready-made alcohol iodine? When using ready-made iodine, the starch will turn black due to high concentration iodine. Accordingly, clarity will be lost: it can be problematic to distinguish between rich brown and black. With a low concentration of iodine in the solution, iodine drops will look slightly yellowish, and places with starch will look blue-violet.

So, put our products on a plate and drip iodine solution on them with a pipette. We observe and discuss what turned blue. Bread, flour, wheat groats and oatmeal stained, but not. We conclude that there is no starch in these vegetables and fruits.

Do you want to play with your child easily and with pleasure?

Experience for children "Intensive coloring"

For this experiment, we need to cook a starch paste. A paste is needed in order to show the baby how the color of starch depends on heat treatment. We take a teaspoon of starch and a glass of water and cook on fire for several minutes until thickened. Pour half of the paste into a glass. Pour 0.5 teaspoon of starch into the second glass of water.

At this moment, the daughter suggested putting another glass of milk, because all the solutions are white. Put milk and began to drip a solution of iodine into each cup. After thorough stirring, the cups were compared according to the intensity of staining: the milk remained white, the starch solution turned light blue, the paste turned deep blue. We made the following conclusions:

1. There is no starch in milk
2. thermally processed starch gives a more intense color, as the starch molecules become more accessible to iodine.

Similar difference in the intensity of staining should also work in the variant: raw - boiled potatoes. If you decide to try, write in the comments what you did!

Experience for children "We cover our tracks"

We open five ampoules of 10% ascorbic acid and pour it into a glass, add water. Now we mix a solution of iodine and a solution of ascorbic acid in one glass, it instantly becomes discolored. We still decided to drop a little more concentrated iodine. You, too, try it - it turns out very beautifully: iodine drops, reacting with ascorbic acid, create a pattern of “bengal lights” on the surface, as my daughter called it. Vitamin C discolored even dyed starch and dyed paste.

This experience was a big surprise for my daughter. She loves to mix colors, mix different colored solutions, and of course she expected the solution to become a little lighter, but not completely discolored. I talked about how we used to mix paints with each other and with water, and now we mix different chemical compounds, they react with each other, and new compounds are obtained, which may differ in color from the original ones. Here we remembered the chemical one, when a lot of foam was released. The daughter understood the analogy.

Experience for children "Drawing on milk"

And finally, we had a creative experience with drawing on the remaining milk, because the child was indignant that the mother had discolored all the colored solutions, and she had nothing to create with. A few drops of gouache were dropped onto the milk. We decided to draw cotton swab and dipped it in dishwashing detergent. It was very interesting to watch how the paint runs away from us and forms bizarre patterns.

The daughter could not stand it and asked: “What have you done? I want to draw, but the paint runs away from me! I figuratively talked about the fact that the dishwashing detergent repels grease, and as they scatter, the fat molecules carry away the paint with them. Having understood the essence, the daughter agreed to “draw” more.

These are all our experiences for today. If you have questions, ask in the comments. I will also be glad to read your ideas for experiments for children with iodine!

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My personal experience teaching chemistry showed that such a science as chemistry is very difficult to study without any initial knowledge and practice. Schoolchildren very often run this subject. I personally observed how a student of the 8th grade at the word "chemistry" began to frown, as if he had eaten a lemon.

Later it turned out that because of dislike and misunderstanding of the subject, he skipped school in secret from his parents. Of course, school program is designed in such a way that the teacher should give a lot of theory at the first chemistry lessons. Practice, as it were, fades into the background precisely at the moment when the student cannot yet independently realize whether he needs this subject in the future. This is primarily due to the laboratory equipment of schools. In big cities, things are better now with reagents and instruments. As for the province, as well as 10 years ago, and at present, many schools do not have the opportunity to conduct laboratory classes. But the process of studying and fascination with chemistry, as well as with other natural sciences, usually begins with experiments. And it is no coincidence. Many famous chemists, such as Lomonosov, Mendeleev, Paracelsus, Robert Boyle, Pierre Curie and Maria Sklodowska-Curie (schoolchildren also study all these researchers in physics classes) have already started experimenting since childhood. The great discoveries of these great people were made in home chemical laboratories, since chemistry classes at institutes were available only to wealthy people.

And, of course, the most important thing is to interest the child and convey to him that chemistry surrounds us everywhere, so the process of studying it can be very exciting. This is where home chemistry experiments come in handy. Observing such experiments, one can further look for an explanation of why things happen this way and not otherwise. And when a young researcher comes across such concepts at school lessons, the teacher’s explanations will be more understandable to him, since he will already have his own experience in conducting home chemical experiments and the knowledge gained.

It is very important to start science studies with the usual observations and real life examples that you think will be the best for your child. Here is some of them. Water is Chemical substance, consisting of two elements, as well as gases dissolved in it. Man also contains water. We know that where there is no water, there is no life. A person can live without food for about a month, and without water - only a few days.

River sand is nothing but silicon oxide, and also the main raw material for glass production.

A person himself does not suspect it and carries out chemical reactions every second. The air we breathe is a mixture of gases - chemicals. In the process of exhalation, another complex substance- carbon dioxide. We can say that we ourselves are a chemical laboratory. You can explain to the child that washing hands with soap is also chemical process soapy water.

An older child who, for example, has already begun to study chemistry at school, can be explained that almost all elements of the periodic system of D. I. Mendeleev can be found in the human body. In a living organism, not only all chemical elements are present, but each of them performs some biological function.

Chemistry is also medicines, without which at present many people cannot live even a day.

Plants also contain the chemical chlorophyll, which gives the leaf its green color.

Cooking is a complex chemical process. Here you can give an example of how the dough rises when yeast is added.

One of the options for getting a child interested in chemistry is to take an individual outstanding researcher and read the story of his life or watch an educational film about him (films about D.I. Mendeleev, Paracelsus, M.V. Lomonosov, Butlerov are now available).

Many believe that real chemistry is harmful substances, experimenting with them is dangerous, especially at home. There are many very exciting experiences that you can do with your child without harming your health. And these home chemical experiments will be no less exciting and instructive than those that come with explosions, pungent odors and puffs of smoke.

Some parents are also afraid to conduct chemical experiments at home due to their complexity or lack of necessary equipment and reagents. It turns out that you can get by with improvised means and those substances that every housewife has in the kitchen. You can buy them at your nearest household store or pharmacy. Test tubes for home chemical experiments can be replaced with pill bottles. Reagents can be stored glass jars, for example, from baby food or mayonnaise.

It is worth remembering that the dishes with reagents must have a label with the inscription and be tightly closed. Sometimes the tubes need to be heated. In order not to hold it in your hands when heated and not get burned, you can build such a device using a clothespin or a piece of wire.

It is also necessary to allocate several steel and wooden spoons for mixing.

You can make a stand for holding test tubes yourself by drilling through holes in the bar.

To filter the resulting substances, you will need a paper filter. It is very easy to make it according to the diagram given here.

For children who do not yet go to school or are studying in elementary grades, setting up home chemical experiments with their parents will be a kind of game. Most likely, such a young researcher will not yet be able to explain some individual laws and reactions. However, it is possible that just such an empirical way of discovering the surrounding world, nature, man, plants through experiments will lay the foundation for the study of natural sciences in the future. You can even arrange original competitions in the family - who will have the most successful experience and then demonstrate them at family holidays.

Regardless of the age of the child and his ability to read and write, I advise you to have a laboratory journal in which you can record experiments or sketch. A real chemist must write down a work plan, a list of reagents, sketches of instruments and describes the progress of work.

When you and your child just begin to study this science of substances and conduct home chemical experiments, the first thing to remember is safety.

For this you need to follow the following rules security:

2. It is better to allocate a separate table for conducting chemical experiments at home. If you do not have a separate table at home, then it is better to conduct experiments on a steel or iron tray or pallet.

3. It is necessary to get thin and thick gloves (they are sold in a pharmacy or hardware store).

4. For chemical experiments, it is best to buy a lab coat, but you can also use a thick apron instead of a dressing gown.

5. Laboratory glassware should not be used for food.

6. In home chemical experiments, there should be no cruelty to animals and violation of the ecological system. Acidic chemical waste should be neutralized with soda, and alkaline with acetic acid.

7. If you want to check the smell of a gas, liquid or reagent, never bring the vessel directly to your face, but, holding it at a certain distance, direct, waving your hand, the air above the vessel towards you and at the same time smell the air.

8. Always use small amounts of reagents in home experiments. Avoid leaving reagents in a container without an appropriate inscription (label) on the bottle, from which it should be clear what is in the bottle.

The study of chemistry should begin with simple chemical experiments at home, allowing the child to master the basic concepts. A series of experiments 1-3 allow you to get acquainted with the main aggregate states substances and properties of water. To begin with, you can show a preschooler how sugar and salt dissolve in water, accompanying this with an explanation that water is a universal solvent and is a liquid. Sugar or salt are solids that dissolve in liquids.

Experience number 1 "Because - without water and neither here nor there"

Water is a liquid chemical substance composed of two elements as well as gases dissolved in it. Man also contains water. We know that where there is no water, there is no life. A person can live without food for about a month, and without water - only a few days.

Reagents and equipment: 2 test tubes, soda, citric acid, water

Experiment: Take two test tubes. Pour in equal amounts of baking soda and citric acid. Then pour water into one of the test tubes, and not into the other. In a test tube in which water was poured, water began to stand out carbon dioxide. In a test tube without water - nothing has changed

Discussion: This experiment explains the fact that many reactions and processes in living organisms are impossible without water, and water also accelerates many chemical reactions. Schoolchildren can be explained that an exchange reaction has taken place, as a result of which carbon dioxide has been released.

Experience number 2 "What is dissolved in tap water"

Reagents and equipment: clear glass, tap water

Experiment: Pour into a clear glass tap water and put it in a warm place for an hour. After an hour, you will see settled bubbles on the walls of the glass.

Discussion: Bubbles are nothing but gases dissolved in water. AT cold water gases dissolve better. As soon as the water becomes warm, the gases cease to dissolve and settle on the walls. A similar home chemical experiment also makes it possible to acquaint the child with the gaseous state of matter.

Experience No. 3 “What is dissolved in mineral water or water is a universal solvent”

Reagents and equipment: test tube, mineral water, candle, magnifying glass

Experiment: Pour mineral water into a test tube and slowly evaporate it over a candle flame (the experiment can be done on the stove in a saucepan, but the crystals will be less visible). As the water evaporates, small crystals will remain on the walls of the test tube, all of them of different shapes.

Discussion: Crystals are salts dissolved in mineral water. They have different shape and size, since each crystal wears its own chemical formula. With a child who has already begun to study chemistry at school, you can read the label on mineral water, which indicates its composition and write the formulas of the compounds contained in mineral water.

Experiment No. 4 "Filtration of water mixed with sand"

Reagents and equipment: 2 test tubes, funnel, filter paper, water, river sand

Experiment: Pour water into a test tube and dip a little river sand into it, mix. Then, according to the scheme described above, make a filter out of paper. Insert a dry, clean test tube into a rack. Slowly pour the sand/water mixture through a filter paper funnel. River sand will remain on the filter, and you will get clean water in a tripod tube.

Discussion: Chemical experience allows us to show that there are substances that do not dissolve in water, for example, river sand. The experience also introduces one of the methods of cleaning mixtures of substances from impurities. Here you can introduce the concepts of pure substances and mixtures, which are given in the 8th grade chemistry textbook. AT this case mixture is sand and water pure substance- filtrate, river sand - this is a sediment.

The filtration process (described in Grade 8) is used here to separate a mixture of water and sand. To diversify learning this process, you can go a little deeper into the cleaning history drinking water.

Filtration processes were used as early as the 8th and 7th centuries BC. in the state of Urartu (now it is the territory of Armenia) for the purification of drinking water. Its inhabitants carried out the construction of a water supply system with the use of filters. Used as filters dense fabric and charcoal. Similar systems of intertwined drainpipes, clay canals, equipped with filters were also on the territory of the ancient Nile among the ancient Egyptians, Greeks and Romans. Water was passed through such a filter several times through such a filter, eventually many times, eventually achieving best quality water.

One of the most interesting experiments is growing crystals. The experience is very clear and gives an idea of ​​many chemical and physical concepts.

Experience number 5 "Grow sugar crystals"

Reagents and equipment: two glasses of water; sugar - five glasses; wooden skewers; thin paper; pot; transparent cups; food coloring (the proportions of sugar and water can be reduced).

Experiment: The experiment should begin with the preparation of sugar syrup. We take a pan, pour 2 cups of water and 2.5 cups of sugar into it. We put on medium heat and, stirring, dissolve all the sugar. Pour the remaining 2.5 cups of sugar into the resulting syrup and cook until completely dissolved.

Now let's prepare the embryos of crystals - sticks. A small amount of sprinkle sugar on a piece of paper, then dip the stick in the resulting syrup, and roll it in sugar.

We take the pieces of paper and pierce a hole in the middle with a skewer so that the piece of paper fits snugly against the skewer.

Then we pour the hot syrup into transparent glasses (it is important that the glasses are transparent - this way the process of crystal ripening will be more exciting and visual). The syrup must be hot or the crystals will not grow.

You can make colored sugar crystals. To do this, add a little food coloring to the resulting hot syrup and stir it.

The crystals will grow in different ways, some quickly and some may take longer. At the end of the experiment, the child can eat the resulting lollipops if he is not allergic to sweets.

If you do not have wooden skewers, then you can experiment with ordinary threads.

Discussion: A crystal is a solid state of matter. It has a certain shape and a certain number of faces due to the arrangement of its atoms. Crystalline substances are substances whose atoms are arranged regularly, so that they form a regular three-dimensional lattice, called a crystal. Row crystals chemical elements and their compounds have remarkable mechanical, electrical, magnetic and optical properties. For example, diamond is a natural crystal and the hardest and rarest mineral. Due to its exceptional hardness, diamond plays a huge role in technology. Diamond saws cut stones. There are three ways to form crystals: crystallization from a melt, from a solution, and from a gas phase. An example of crystallization from a melt is the formation of ice from water (after all, water is molten ice). An example of crystallization from solution in nature is the precipitation of hundreds of millions of tons of salt from sea water. In this case, when growing crystals at home, we are dealing with the most common methods artificial cultivation- crystallization from solution. Sugar crystals grow from a saturated solution by slowly evaporating the solvent - water, or by slowly lowering the temperature.

The following experience allows you to get at home one of the most useful crystalline products for humans - crystalline iodine. Before conducting the experiment, I advise you to watch with your child a short film “The life of wonderful ideas. Smart iodine. The film gives an idea of ​​the benefits of iodine and the unusual story of its discovery, which will be remembered by the young researcher for a long time. And it is interesting because the discoverer of iodine was an ordinary cat.

The French scientist Bernard Courtois during the years of the Napoleonic Wars noticed that in the products obtained from the ashes of seaweed, which were thrown onto the coast of France, there is some substance that corrodes iron and copper vessels. But neither Courtois himself nor his assistants knew how to isolate this substance from the ashes of algae. Chance helped speed up the discovery.

At his small saltpeter plant in Dijon, Courtois was going to conduct several experiments. There were vessels on the table, one of which contained an alcoholic tincture of seaweed, and the other a mixture of sulfuric acid and iron. On the shoulders of the scientist sat his beloved cat.

There was a knock on the door, and the frightened cat jumped down and ran away, brushing the flasks on the table with its tail. The vessels broke, the contents mixed, and suddenly a violent chemical reaction began. When a small cloud of vapors and gases settled, the surprised scientist saw some kind of crystalline coating on the objects and debris. Courtois began to explore it. Crystals to anyone before this unknown substance were called "iodine".

So it was opened new element, a domestic cat Bernard Courtois has gone down in history.

Experience No. 6 "Obtaining iodine crystals"

Reagents and equipment: tincture of pharmaceutical iodine, water, a glass or a cylinder, a napkin.

Experiment: We mix water with tincture of iodine in the proportion: 10 ml of iodine and 10 ml of water. And put everything in the refrigerator for 3 hours. During cooling, the iodine will precipitate at the bottom of the glass. We drain the liquid, take out the iodine precipitate and put it on a napkin. Squeeze with napkins until the iodine begins to crumble.

Discussion: This chemical experiment is called extraction or extraction of one component from another. In this case, the water extracts the iodine from the spirit lamp solution. Thus, the young researcher will repeat the experience of the cat Courtois without smoke and beating dishes.

Your child will already learn about the benefits of iodine for disinfecting wounds from the movie. Thus, you show that there is a difference between chemistry and medicine. inseparable bond. However, it turns out that iodine can be used as an indicator or analyzer of the content of another beneficial substance- starch. The following experience will introduce the young experimenter to a separate very useful chemistry - analytical.

Experience No. 7 "Iodine-indicator of starch content"

Reagents and equipment: fresh potatoes, pieces of banana, apple, bread, a glass of diluted starch, a glass of diluted iodine, a pipette.

Experiment: We cut the potatoes into two parts and drip diluted iodine on it - the potatoes turn blue. Then we drip a few drops of iodine into a glass of diluted starch. The liquid also turns blue.

We drip with a pipette iodine dissolved in water on an apple, banana, bread, in turn.

Watching:

The apple didn't turn blue at all. Banana - slightly blue. Bread - turned blue very much. This part of the experiment shows the presence of starch in various products.

Discussion: Starch, reacting with iodine, gives a blue color. This property gives us the ability to detect the presence of starch in various foods. Thus, iodine is, as it were, an indicator or analyzer of starch content.

As you know, starch can be converted into sugar, if you take an unripe apple and drop iodine, it will turn blue, since the apple is not yet ripe. As soon as the apple ripens, all the starch contained will turn into sugar and the apple does not turn blue at all when treated with iodine.

The following experience will be useful for children who have already started studying chemistry at school. It introduces concepts such as chemical reaction, compound reaction, and qualitative reaction.

Experiment No. 8 "Flame coloring or compound reaction"

Reagents and equipment: tweezers, cookware edible salt, spirit lamp

Experiment: Take with tweezers a few large crystals table salt table salt. Let's hold them over the flame of the burner. The flame will turn yellow.

Discussion: This experiment allows chemical reaction combustion, which is an example of a compound reaction. Due to the presence of sodium in the composition of table salt, during combustion, it reacts with oxygen. As a result, a new substance is formed - sodium oxide. The appearance of a yellow flame indicates that the reaction has passed. Such reactions are qualitative reactions to compounds containing sodium, that is, it can be used to determine whether sodium is present in a substance or not.

From this article you will learn how the reaction of starch and iodine proceeds. This interesting chemical process has practical use. For example, it helps to find out if starch is contained in a particular product.

Let's first understand what starch is.

It's tasteless White powder, in its consistency reminiscent of flour. The formula of starch (amylose and amylopectin polysaccharide) is (C₆H₁₀O₅)n.

Starch is the result of a natural process called photosynthesis. For plants, it serves as a kind of reserve nutrients, for the human body - a supplier of important carbohydrates.

Physical properties of starch

Insoluble in cold water. If you press the powder with a spoon, thereby pressing it, then a characteristic creak is heard, due to the friction of the microparticles against each other.

Chemical properties of starch

AT hot water(C₆H₁₀O₅)n also does not dissolve, but swells to a thick and viscous substance, forming a colloidal mixture called a paste. A solution of starch in water is a non-Newtonian fluid.

If you add acids to the water where the starch is (for example, H₂SO₄), then you can observe the process of hydrolysis with a decrease molecular weight substances and the formation of "soluble" starch.

Starch molecules are heterogeneous in their structure.

Starch is also a polyhydric alcohol that forms ethers and esters during intermolecular dehydration and esterification.

Industrially, starch is obtained from wheat, potatoes, corn and rice.

However, it is easy to get it at home.

Application of starch

Starch is widely used for industrial purposes. It finds use in the production of substances such as glucose, molasses and ethanol.

Starch is also widely used in textile production. They process fabrics. In paper mills, starch acts as a hydrophilic agent - a material that increases strength and improves the typographic quality of paper. It is also used for the manufacture of medicines and food.

In everyday life, almost all of us use this substance: we starch, cook jelly, make a paste (a mixture of starch with water and flour), etc.

The reaction of starch and iodine

For this experience, we will take 5% alcohol solution, which is used in medicine - it is with him that most reactions are carried out in laboratories.

Starch reacts with iodine to form inclusion compounds, that is, clathrate. This chemical process was discovered back in 1814 by the scientists Jean-Jacques Colin and Henri-Francois Gauthier de Clobri.

An inclusion compound is a special compound in which molecules of one substance are introduced into molecular structure another substance.

In this case, amylose molecules (one of the main starch polysaccharides) will be the “hosts”, and iodine molecules will be the “guests”. Click to see more unusual experiments with iodine.

Experience with starch and iodine at home

This is a fairly simple chemistry experiment that can be done at home and shown to children to instill in them a love of chemistry.

This will require:

• glass test tube;
• alcohol solution of iodine;
• a pinch of starch;
• water at room temperature;
• stirring stick.

Pour water into a test tube and drop 4-5 drops of iodine into it. Add a pinch of starch and mix well with a stick. As a result, you will immediately get a dark blue solution.

By the way, this experiment can be repeated in another way. For example, drop one drop of iodine into a small hill of starch, resulting in a dark blue spot. You can also drop iodine on half a potato (known high content starch). If you put a peeled potato in cold water, after a while, particles of starch will appear in the water. If you hold peeled potatoes in your hands, starch will also remain on them.

By the way, if you then heat a test tube with a solution of starch, iodine and water on a special chemical burner for 10 seconds, the solution will become colorless. This is due to the fact that the combination of iodine and starch is unstable, but if you hold the test tube in cold water, a dark blue precipitate will form again.

When starch is heated to boiling, it begins to break down, and the amylose chains will break. This is how short chains of dextrins are formed, so the color starts to change. By the way, individual glucose compounds do not give color when reacting with iodine.

The equation for the reaction of iodine and starch looks like this:

I₂ + (C₆H₁₀O₅)n => I₂ (C₆H₁₀O₅)n

An interesting fact: amylopectin, a starch polysaccharide, when interacting with I₂, gives a purple-red color. There is much more amylopectin in starch than amylose, which gives a blue color, but the blue color overlaps the red-violet.

Consider how the reaction to starch with iodine can be useful in life.

It's simple: if you have two unsigned jars of soda and starch and you don't want to taste these substances, drop a little iodine.

Also, due to the viscous structure of starch, it is added to fake some. This is especially true for honey: on the market you can find fakes with great content(C₆H₁₀O₅)n. Starch can be detected with the same simple chemical method in any food.