Introduction

Many living organisms are capable of causing serious damage to humans, pets, plants, as well as destroying non-metallic, metallic materials and products made from them.

Of the many methods of plant protection, the most important is the chemical method - the use of chemical compounds that destroy harmful organisms. The chemical method is also effective for protecting various materials and products from biological destruction. Recently, pesticides have been widely used in the fight against various pests.

Pesticides (lat. Pestis - infection and lat. Caedo - kill) are chemicals used to fight harmful organisms.

Pesticides combine the following groups of such substances: herbicides that destroy weeds, insecticides that destroy insect pests, fungicides that destroy pathogenic fungi, zoocides that destroy harmful warm-blooded animals, etc.

Most pesticides are poisons that poison the target organisms, they also include sterilizers (substances that cause infertility) and growth inhibitors.

2.1 Copper sulfate and its properties

Copper sulfate CuSO 4 crystallizes from aqueous solutions of copper sulfate and is a bright blue crystals of the triclinic system with lattice parameters. Density 2, 29 g / cm3.

When heated above 105 ° C, it melts with the loss of a part of crystallization water and passes over to CuSO 4. 3H 2 O (blue) and CuSO 4 H 2 O (white). Fully dehydrated at 258 ° C. When dry NH 3 acts on CuSO 4, CuSO 4 5NH 3 is formed, which exchanges NH 3 for H 2 O in humid air. With alkali metal sulfates, CuSO 4 forms double salts of the Me 2 SO 4 CuSO 4 6H 2 O type, colored greenish.

In industry, copper sulfate is obtained by dissolving metallic copper in heated diluted H 2 SO 4 by blowing air: Cu + H 2 SO 4 + ½O 2 = CuSO 4 + H 2 O. It is also a by-product of electrolytic copper refining.

Copper sulfate is the most important technical copper salt. It is used in the production of mineral paints, wood impregnation, for the control of pests and plant diseases in agriculture, for grain pickling, for leather dressing, in medicine, in galvanic cells; serves as a starting product for the preparation of other copper compounds.

Copper sulfate (copper sulfate) CuSO 4 - colorless crystals 3.64 g / cm3. When heated, dissociate: CuSO 4 = CuO + SO 2 + ½O 2 with the formation of the basic sulfate CuO CuSO 4 as an intermediate product. At 766 ° C, the dissociation pressure of CuSO 4 reaches 287 mm. rt. column, and CuO CuSO 4 - 84 mm. rt. pillar. The solubility of CuSO 4 in grams per 100 g of water is: 14 (0 ° C); 23.05 (25 ° C); 73.6 (100 ° C). In the presence of free H 2 SO 4, the solubility decreases. At pH 5.4-6.9, CuSO 4 is hydrolyzed to form basic salts. CuSO 4 is very hygroscopic, therefore it is used as a drying agent; adding water, turns blue, which is sometimes used to detect water in alcohol, ether and others.

When heated, copper sulfate loses water and turns into a gray powder. If, after cooling, you drop a few drops of water on it, then the powder will again acquire a blue color.

2.2 Iron sulfate and its properties

Ferrous sulfate (2)

The systematic name of Iron 2 is tetraoxocyosulfate.

Physical properties: crystalline state, molar mass 151.932 g / mol, density - 1.898 g / cm3

Iron sulfate (2), iron (2) sulfate-inorganic binary compound, iron salt of sulfuric acid with the formula FeSO 4. FeSO 4 ∙ H 2 O heptahydrate has the trivial name iron vitriol. Crystalline hydrates are hygroscopic transparent crystals of light bluish-green color, colorless FeSO 4 ∙ H 2 O monohydrate (smolnokite). Strongly astringent ferrous (metallic) taste. In air, they gradually erode (lose crystallization water). Ferrous sulfate (‖) is highly soluble in water. A bluish-green heptahydrate crystallizes from aqueous solutions. The toxicity of ferrous sulfate is relatively low.

It is used in the textile industry, in agriculture as a fungicide, for the preparation of mineral paints.

Properties.

Ferrous sulfate is released at temperatures from 1.82˚C to 56.8˚C from aqueous solutions in the form of light green crystals of crystalline hydrate FeSO 4 ∙ 7H 2 O, which is called iron vitriol in technology. In 100 g of water dissolves: 26.6 g of anhydrous FeSO 4 at 20˚C and 54.4 at 56˚C.

Solutions of ferrous sulfate (‖) under the influence of atmospheric oxygen are gradually oxidized, turning into ferrous sulfate (׀׀׀):

12FeSO 4 + 3O 2 + 6H 2 O → 4 Fe 2 (SO 4) 3 + Fe (OH) 3 ↓

Decomposes on heating over 480˚C:

2FeSO 4 → Fe 2 O 3 + SO 2 + SO 3

Receiving

Iron sulfate can be prepared by the action of dilute sulfuric acid on scrap iron, roofing iron trim, etc. In industry, it is obtained as a by-product during pickling of iron sheets, wire, descaling and other diluted H 2 SO 4.

Fe + H 2 SO 4 → FeSO 4 + H 2

Another way is oxidation pyrite roasting:

FeS 2 +3 O 2 → FeSO 4 + SO 2

They are used in the manufacture of ink, in dyeing (for dyeing wool black), for wood preservation.

2.3 Bordeaux liquid (copper sulfate + calcium hydroxide)

Chemical formula СuSO 4 3Cu (OH) 2

Bordeaux liquid, Bordeaux mixture (copper sulfate + calcium hydroxide) - pesticide, protective contact fungicide and bactericide. In higher doses, it has an eradicating effect on dormant forms of plant pathogens. It is used for early spring treatments of orchards, for vineyards, berry fields by spraying.

Physicochemical properties

Bordeaux mixture - basic copper sulfate with an admixture of gypsum. A properly prepared suspension is quite stable, has good adhesion, retention on the surface of plants and high fungicidal activity. It is a blue liquid, which is a suspension of colloidal particles of the active substance - metallic copper. A properly prepared preparation should have a neutral or slightly alkaline reaction. A strongly alkaline preparation is poorly adhered to the surface of plants, and a strongly acidic phytocidene. The reaction of the solution is established by immersing an iron wire or a nail in it: in an acidic medium, a coating of copper appears on them, and in this case it is necessary to add milk of lime to the solution. To increase the adhesive properties, liquid glass (silicate glue), casein glue, molasses, sugar, skimmed milk, eggs and synthetic surfactants are sometimes added to the Bordeaux liquid.

Bordeaux mixture is made from copper sulphate and lime. Here are the physical and chemical properties of each of these substances.

СuSO 2 - copper (II) sulfate. The substance is white, very hygroscopic, low-melting, decomposes upon strong heating. Crystalline hydrate СuSO 4 3H 2 O (chalcanthite, copper sulfate) has the structure [Сu (H 2 O) 4] SO 4 H 4 O.

It dissolves well in water (cation hydrolysis). Reacts with ammonia hydrate, alkalis, active metals, hydrogen sulfide. It enters into complexation and exchange reactions.

Physical characteristics of CuSO 4

Molecular weight 159.6 g / mol;

Melting temperature ~ 200 ° С;

Relative density 3, 603g / cm3 (at room temperature).

Ca (OH) 2 - calcium hydroxide, slaked lime. The substance is white, decomposes on heating without melting. It dissolves poorly in water (a dilute alkaline solution is formed). Reacts with acids, shows basic properties. Absorbs CO 2 from the air.

Physical characteristics of Ca (OH) 2

Molecular weight 74.09 g / mol;

Relative density 2.08 g / cm3 (at room temperature).

Effects on pests

The fungicidal effect of Bordeaux liquid is due to the fact that during hydrolysis under the influence of air carbon dioxide, secretions of fungi and plants, the basic salt of copper sulfate decomposes and releases copper sulfate in small quantities:

CuSO 4 Cu (OH) 2 + H 2 O + 3CO 2 → CuSO 4 + 3CuCO 3 + 4Н 2 О

If this process is intense (at high humidity and temperature), then the protective effect of the fungicide will be short-lived, and damage to plants is possible.

The last processing period for most crops ends 15 days before harvesting, melons - 5 days, tomatoes - 8 days before harvesting, subject to careful sprinkling during harvesting.

Bordeaux liquid is one of the universal fungicides with the longest duration of protective action (up to 30 days). In almost all cases, it has a stimulating effect on plants. The effectiveness of the drug depends on the duration of its use. The best results are obtained from treatments shortly before infection. According to other literature data, it is more advisable to use the drug in the late autumn period and at the beginning of bud break. In these cases, it has almost no negative effect on the protected crop (phytotoxicity is lower).

When plants are treated with Bordeaux liquid, the main copper sulfate falls out in the form of a gelatinous sediment, which adheres well to the leaves and covers them and the fruits of plants with a protective layer. Bordeaux liquid ranks first among fungicides in terms of retention on leaves. Possesses repellent properties for many insects.

Mechanism of action.

The biological properties of copper-containing preparations are determined by the ability of copper ions to actively react with lipoprotein and enzymatic complexes of living cells, causing irreversible changes (coagulation) of protoplasm. Copper ions that enter the cells of the pathogen in a sufficiently high concentration interact with various enzymes that contain carboxyl, imidazole and thiol groups, and suppress their activity. At the same time, first of all, the processes included in the respiratory cycle are inhibited. They also cause non-specific denaturation of proteins. Their selectivity in relation to useful organisms depends on the amount of copper ions that enter the cells and accumulate in them. Conidia and fungal spores, growing on the surface of plants in a drop of water, are capable of concentrating copper ions inside their cells, creating a concentration 100 or more times higher than in plant cells or outside.

Bordeaux mixture for many insects has repellent properties.

Resistant species.

Bordeaux mixture is not effective against the downy mildew and tobacco, as well as against powdery mildew.

Insecticidal and acaricidal properties. Bordeaux mixture for many insects has repellent properties.

Suppresses leaf beetles on potatoes. Shows an ovicidal effect.

Application

Bordeaux liquid ranks first among protective fungicides in adhesion and retention on the surface of plants. However, due to the high consumption of copper sulfate, the difficulty of preparation, and the possibility of damage to plants, this fungicide is replaced with copper oxychloride and organic preparations.

Registered preparations based on Bordeaux mixture are approved for use in agriculture and personal subsidiary farms against diseases of sugar beet, fodder, canteen (cercosporosis), onion (peronosporosis), apricot, peach, plum, cherry, cherry (coccomycosis, curl, moniliosis), gooseberry (anthracnose, rust, septoria), etc.

Bordeaux liquid must not be mixed with organophosphate insecticides and other preparations that decompose in an alkaline environment.

Phytotoxicity: On the surface of plants in the presence of droplet-liquid moisture, particles of basic copper sulfate are slowly hydrolyzed, and copper ions enter the water in a relatively small amount. In this case, the risk of plant burns is significantly reduced. Such burns occur only with a significant increase in concentration, poor quality of Bordeaux mixture, increased precipitation after treatment or acidic air pollution. Also, in case of improper preparation of the drug, it is possible to suppress growth and the appearance of a "mesh" on the leaves and fruits.

The drug causes the crushing of cherry fruits with an increase in the content of sugars and dry matter, the formation of a "net" on the fruits and leaves of apple varieties sensitive to copper, "burns" the leaves and reduces the survival rate of budding due to drying of the rootstocks bark. Heavy rainfall contributes to the damage. Phytocidal activity also increases with the age of the trees. On the Dyber cherry variety, the Bordeaux liquid, black with sharp temperature fluctuations and drought, contributed to summer leaf fall, oppression of trees.

Toxicological properties and characteristics

Entomophages and useful species. The drug is low-toxic for bees, however, it is better to isolate the bees for the period of treatment of crops and in the next 5 hours to one day. It is quite toxic for the predatory mite Anistis (when applied at a concentration of 0.09%, its abundance on black currant decreased by 3-4 times). It is weakly toxic for Entsirtids and moderately toxic for Trichogrammatids. At a concentration of 1%, it is low-toxic for pupariums of Encarsia. The period of residual action for adults is no more than a day. Moderately toxic to Creptolemus.

The mixture is not poisonous for other predatory mites, coccinellids, larvae and imago of lacewings, carnivorous gall midges and such hymenoptera as aphenilids, pteromalids, and their nevmonids.

Warm-blooded. Bordeaux liquid has low toxicity for warm-blooded animals and humans. According to other literary sources, the drug for warm-blooded animals is moderately toxic: oral LD50 for mice 43 mg / kg, for rats 520 mg / kg. The concentrated preparation irritates the mucous membranes.

Poisoning symptoms

Eating the fruit for the first time days after treatment with preparations containing copper sulfate causes nausea and vomiting.

Preparation of the solution

Bordeaux mixture is obtained by mixing a solution of copper sulfate with a slurry of quicklime. The quality of the mixture prepared depends on the ratio of the components, the quality of the quicklime and the preparation procedure. High quality is ensured when the ratio of the components is 1: 1 or 4: 3 and the reaction proceeds in an alkaline environment. Preparation consists in slowly pouring a copper sulfate solution in a small stream into a lime suspension. Constant stirring is required. The resulting dark blue liquid should resemble diluted jelly.

If this process is disturbed, the content of copper hydroxide, oxidized on the surface to insoluble copper oxide, increases in the mixture, and the number of large (up to 10 μm) particles increases, which reduces the stability and adhesion of the drug. The complexity of preparation and the need for equipment for this are the disadvantages of the Bordeaux mixture.

To prepare 100 liters of a 1% preparation, take 1 kg of copper sulfate and 0.75 kg of quicklime (if the lime is of poor quality - up to 1 kg). Copper sulfate is dissolved in a small volume of hot water and brought up to 90 liters with water. Quicklime is quenched by adding water to it, until a creamy mass is formed first, and then lime milk, the volume of which is also brought to 10 liters with water. Milk of lime is poured with constant stirring to a solution of copper sulfate. With the specified recipe, it is also allowed to add a solution of copper sulfate to the milk of lime, but you cannot mix strong solutions of these components, and also pour a strong solution of copper sulfate into a weak solution of milk of lime. In these cases, spherical crystals of basic copper sulfate are formed, which are easily washed off from plants by sediments. A similar phenomenon is observed with aging of the drug.

For the preparation of Bordeaux liquid, containers made of corrosive materials must not be used.

Bordeaux mixture is prepared immediately before use and only in the required concentration. Do not dilute the prepared solution with water, as in this case it quickly exfoliates. During long-term storage, aggregation of Bordeaux mixture particles occurs, causing their precipitation and poor retention on plants.

Today, manufacturing firms offer Bordeaux mixture in powder form. It is prepared by complete neutralization of copper sulfate with slaked lime, dried and micronized. Due to the special fineness of the particles, the working composition has maximum adhesion, and the resulting suspension is very stable.

Introduction

In a building supplies store you saw a bucket with an unknown name "Mineral Paint". Curiosity takes over, and your hand reaches out to him. We read the composition: "Lime, kitchen salt, etc., etc. ..." What else is copper sulfate ?! "- eyes caught the name of an unfamiliar substance. Others would have given up on it, but not you. Surely you want to know more about him. Therefore, the topic of today's article will be copper sulfate.

Definition

Due to the variable valence of copper, only two of its sulfates exist in chemistry - I and II. We will now talk about the second sulfate. It is an inorganic binary compound and is a copper salt of sulfuric acid. Such copper sulfate (formula CuSO 4) is also called copper sulfate.

Properties

It is a non-volatile, colorless, opaque and highly hygroscopic, odorless substance. However, the properties of the crystalline hydrates of copper sulfate themselves differ significantly from its features (as a substance). They look like transparent, non-hygroscopic crystals, which have various shades of blue (photo above) and a bitter-metallic taste. Also, copper sulfate is highly soluble in water. If you crystallize its aqueous solutions, you can get copper sulfate (photo). Hydration of anhydrous copper sulphate is an exothermic reaction in which significant heat is generated.

Receiving

In industry, it is obtained contaminated by dissolving copper and copper waste in dilute sulfuric acid, which, in addition, is blown with air.
Also, copper sulfate can be obtained in the laboratory in several ways at once:

• Sulfuric acid + copper (when heated).
• Sulfuric acid + copper hydroxide (by neutralization).

Cleaning

To purify the copper sulfate obtained by such methods, recrystallization is most often used - it is immersed in boiling distilled water and kept on fire until the solution becomes saturated. Then it is cooled to +5 about C and the resulting precipitate resembling crystals is filtered off. However, there are methods for deeper cleaning, but they already require other substances.

Copper sulfate: application

With the help of anhydrous copper sulfate, ethanol is absorbed and gases are dried; it also serves as a moisture indicator. In construction with an aqueous solution of copper sulphate, they neutralize the effects of leaks, eliminate rust stains and remove salt emissions from plastered, brick and concrete surfaces, as well as prevent wood decay. In the agricultural sector, copper sulfate, formed from copper sulfate, serves as an antiseptic, fungicide and copper-sulfur fertilizer. Plants, trees and soil are disinfected with solutions of this substance (with different concentrations). Bordeaux liquid, well-known to farmers, also partially consists of copper sulfate. It is also one of the ingredients that make up mineral paints. Do not do without it in the production of acetate fibers. Copper sulfate is also known as a food additive E519, used as a color fixative and preservative. Also, a solution of copper sulfate can detect zinc, manganese in aluminum alloys and stainless steel: if they contain the above impurities, then red spots will appear on their surface when they come into contact with this solution.

Conclusion

Copper (II) sulfate itself is little known, but everyone has heard about the product of its reaction with water - copper sulfate. And, as you can see, it is very useful.

That is, water molecules are also included in the structure of this substance. It possesses the same basic properties that are characteristic of ordinary copper sulfate. It should be said that this is a salt, therefore it has a chemical behavior that is characteristic of many other substances in this group.

Physical properties

Copper sulfate is a blue solid crystalline substance. It is soluble in water. There are five water molecules per one molecule of copper sulfate in the structure of the substance. Anhydrous, it does not have any color. It can be found naturally in the form of some minerals such as chalcanthite. This stone is little known and rarely used.

Chemical properties of copper sulfate (copper sulfate)

Like any other sulfate, copper can decompose when exposed to high temperatures. This type of reaction produces cuprum oxide, sulfur dioxide and oxygen. Also, copper sulfate, like other salts, can be a participant in the substitution reaction. With this kind of interaction, the more active metal, which is to the left of the cuprum in the electrochemical series of activity, displaces the copper atom from the compound and takes its place. For example, by adding sodium to the substance in question, you can get sodium sulfate and copper, which will precipitate. In addition, this substance is capable of reacting with basic and acidic hydroxides, as well as other salts. An example is the reaction of copper sulfate with calcium hydroxide, the base. As a result of this interaction, copper hydroxide and calcium sulfate are released. As an example of the reaction of this salt with an acid, one can take its interaction with phosphoric, as a result of which copper phosphate and sulfate acid are formed. When copper sulfate is mixed with a solution of another salt, an exchange reaction occurs. That is, if you add to it, for example, barium chloride, you can get copper chloride and barium sulfate, which precipitates (if one of the products is not a precipitate, gas or water, the reaction cannot take place).

Getting this substance

Copper sulfate can be obtained using two main methods. The first is the interaction of copper hydroxide with concentrated sulfate acid. At the same time, a significant amount of water is also released, part of which is used for hydration. The second method of obtaining this substance is the interaction of concentrated sulfuric acid directly with copper. This kind of reaction can only take place under specific conditions in the form of an elevated temperature. It is also possible to carry out a reaction between copper oxide and sulfate acid, which also results in the desired substance and water. In addition, copper sulfate is obtained by roasting copper sulfites.

The use of copper sulfate

This substance has found its main application in the horticultural field - it is used to protect plants from diseases and pests thanks to its antiseptic and disinfectant agents. Also, this substance is widely used in agriculture, since it can be used to increase the frost resistance and immunity of plants to fungi. In addition, copper sulfate is used in metallurgy, as well as in construction. It is impregnated with wood to give it fireproof properties. In the food industry, it is often used as a preservative. In addition to all of the above, copper sulfate is used for the manufacture of paints, for high-quality reactions to cations of zinc, manganese and magnesium.

Copper sulfate crystals

Growing crystals from various substances is an interesting and exciting activity for children. The raw material for such an entertaining experiment can be many different compounds, including kitchen salt and copper sulfate. The properties of this substance make it possible to grow a large crystal from its powder purchased in any gardening store. This will not require too much effort. To grow a crystal of copper sulfate, you need to take any container. Water should be poured into it and the powder itself should be poured, while heating the liquid in order to facilitate faster dissolution of the substance in it. It is necessary to add copper sulfate as long as it can be dissolved in water. This way we get a very saturated solution. Then you can leave it like this, just covering it with something, or you can fasten a thread with a bead or button suspended from it on the lid on the inside, so that it hangs evenly - this way the crystals will grow on the thread, and not at the bottom of the container. It is necessary to ensure that it is not moved from place to place, otherwise it will not work. Every day or every few days, you need to gradually add copper sulfate to the solution to maintain a high saturation, so that the crystals do not begin to dissolve in water again. After about two weeks of such manipulations, if done correctly, you can get a rather large crystal.

Copper sulfate. Qualitative reactions carried out with its help

With the help of this substance, the presence of zinc cations can be determined. If you add copper sulfate to the solution, and a cloudy precipitate will fall out, then it contains zinc compounds. Also, using the substance in question, you can determine the presence of magnesium cations. In this case, a precipitate will also form in the solution.

How to determine that there is copper sulfate in the solution?

The most common quality reaction that can be carried out at home is the interaction of the solution with iron. You can take any iron product. If, after dipping it into the solution for a while, you see a reddish bloom on it, then copper sulfate is present. This plaque is copper that has settled on the iron product. Ferrous sulfate, which is also released as a result of this substitution reaction, goes into the test solution. Another, already less accessible option for determining the presence of a given substance in a solution is the reaction with any soluble barium salt. This will precipitate barium sulfate. It is also possible to carry out the test using any aluminum product according to the same principle as the first described reaction. In this case, a reddish bloom should also form, which indicates the replacement of copper atoms by aluminum atoms and the formation of aluminum sulfate and pure copper.

Conclusion

If we briefly summarize everything written above, we can say that copper sulfate is a very widespread and well-known substance that is used in many areas of human life. It can be used in a wide variety of industries and at home: for entertainment purposes or for plant care. Also, this substance is popular with those who breed fish - it protects the aquarium from microalgae contamination. Cuprum sulfate is easy to obtain in the laboratory. It has a low cost, as a result of which it has become so widespread and is used for a variety of purposes.

Blue crystals of copper sulfate turn white when heated

Complexity:

Danger:

Do this experiment at home

Reagents

Security

• Wear protective gloves and goggles before starting the experiment.
• Run the experiment on a tray.
• During the experiment, keep a container of water nearby.
• Place the burner on the cork base. Do not touch the burner immediately after completing the experiment - wait until it cools down.

General safety rules

• Do not allow chemicals to come into contact with eyes or mouth.
• Keep people without safety glasses, small children and animals away from the testing area.
• Store the experimental kit out of the reach of children under 12 years of age.
• Wash or clean all equipment and accessories after use.
• Make sure all reagent containers are tightly closed and stored properly after use.
• Make sure all disposable containers are properly disposed of.
• Use only equipment and reagents supplied in the kit or recommended by the current instructions.
• If you used a food container or utensil for experimentation, discard it immediately. They are no longer suitable for storing food.

First aid information

• If reagents come in contact with eyes, flush eyes thoroughly with water, keeping eye open if necessary. See a doctor immediately.
• If swallowed, rinse your mouth with water and drink some clean water. Do not induce vomiting. See a doctor immediately.
• If reagents are inhaled, remove to fresh air.
• In case of skin contact or burns, rinse the affected area with copious amounts of water for 10 minutes or longer.
• If in doubt, consult a doctor immediately. Take the chemical and its container with you.
• Always see a doctor in case of injury.

• Improper use of chemicals can cause injury and damage to health. Perform only the experiments specified in the instructions.
• This set of experiences is only for children 12 years of age and older.
• Children's abilities vary significantly even within the age group. Therefore, it is up to parents who experiment with their children to decide which experiments are appropriate and safe for their children.
• Parents should discuss safety rules with the child or children before starting experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
• Before starting experiments, clear the testing area of ​​objects that may interfere with you. Storing food near the test site should be avoided. The test site should be well ventilated and close to a tap or other source of water. A stable table is required to conduct experiments.
• Substances in single-use packaging should be used completely or disposed of after one experiment, i.e. after opening the package.

FAQ

Blue crystals do not turn white. What to do?

Has passed 10 - 15 minutes, but the crystals of copper sulfate CuSO 4 do not turn white? It looks like there is something wrong with the heating of the mold. Check if the candle is lit. Remember to place the mold in the center of the flame diffuser and the candle in the center of the burner.

Don't get dirty!

Be careful: the candle flame smokes the bottom of the mold quite strongly. It quickly turns black and it is easy to get dirty on it.

Do not flood with water!

Do not pour copper sulfate aluminum mold with water! This can lead to violent processes: aluminum will recover, releasing hydrogen gas. You can learn more about this reaction in the scientific description of the experiment (section "What happened").

Other experiments

Step-by-step instruction

1. Place three candles in a dry fuel burner and light them. Cover the burner with a diffuser and cover the top with foil.
2. Place an aluminum mold on top of the foil. Pour one large spoonful of copper sulfate crystalline hydrate CuSO 4 5H 2 O into it.
3. Watch the color change of the crystals: after 5 minutes, the blue crystals will turn blue, and after another 10 - white.

Expected Result

When heated, the water that is part of the copper sulfate hydrate leaves the crystals and evaporates. The result is white anhydrous copper sulfate.

Disposal

Dispose of solid waste from the experiment with your household waste.

What happened

Why does the color of copper sulfate change?

Any change in color tells us that the structure of the substance has changed, because it is it that is responsible for the very presence of color. From the formula of the initial copper sulfate CuSO 4 5H 2 O, it can be seen that, in addition to the sulfate CuSO 4 itself, this blue crystalline substance also contains water. Such solids, which include water molecules, are also called hydrates *.

Water is associated in a special way with copper sulfate. When we heat this hydrate, the water is removed from it, almost like a kettle of boiling water. This destroys the bonds of water molecules with copper sulfate. This is manifested in a change in color.

To learn more

Let's start with the fact that water molecules are polar, that is, non-uniform in terms of charge distribution. What does it mean? The fact is that on one side of the molecule there is a slight excess of a positive charge, and on the other - a negative one. These charges add up to zero - after all, molecules, as a rule, are not charged. But this does not prevent some of their parts from carrying positive and negative charges.

Compared to hydrogen, oxygen atoms attract negatively charged electrons better. Therefore, from its side, a negative charge is concentrated in a water molecule, and from the other side - a positive charge. This uneven distribution of charges makes its molecules dipoles(from the Greek "dis" - two, "polos" - pole). This "two-faced" water allows it to easily dissolve compounds such as NaCl or CuSO 4, because they are composed of ions (positively or negatively charged particles). Water molecules can interact with them, turning towards positively charged ions with their negatively charged side (that is, an oxygen atom), and towards negatively charged ions with their positively charged side (that is, hydrogen atoms). And all the particles feel very comfortable with each other. That is why compounds, which are composed of ions, usually dissolve well in water.

Interestingly, during the crystallization of many compounds from aqueous solutions, this interaction is partly retained in the crystal, as a result of which a hydrate is formed. Copper ions, as we can see from all the experiments of this set, strongly change their color depending on what particles they are surrounded by.

Both the copper sulfate solution and the CuSO 4 * 5H 2 O hydrate have approximately the same saturated blue color, which can tell us that copper ions in both cases are in the same or at least similar environment.

Indeed, in solution copper ions are surrounded by six water molecules, while in hydrate Cu 2+ ions are surrounded by four water molecules and two sulfate ions. Another water molecule (after all, we are talking about pentahydrate) remains bound with sulfate ions and other water molecules, which in many respects resembles its behavior in a saturated (that is, the most concentrated) solution of copper sulfate.

When we heat a hydrate, the water molecules have a choice. On the one hand, there are wonderful copper ions - quite pleasant and pretty neighbors. And sulfate ions are also a very decent company. On the other hand, what water molecule does not dream of free flight and knowledge of unknown distances? When the temperature rises, the situation in the hydrate heats up, and the company is no longer as decent as the water molecules would like. And they have more energy. Therefore, at the earliest opportunity, they leave copper sulfate, which in fact has become a living hell.

When all the water from the hydrate evaporates, only sulfate ions remain surrounded by copper ions. This leads to the fact that the color of the substance passes from blue to white.

Can blue be returned?

Yes, you can. There is a lot of water in the vapor state in the air around us. And we ourselves exhale water vapors - remember how glass fogs up if you breathe on it.

If the temperature of copper sulfate has returned to room temperature, water can "settle" on it in much the same way as on glass. In this case, it will again bind in a special way with copper sulfate and gradually return its blue color.

You can also speed up this process. If you put the dried copper sulfate together with a glass of water in one closed container, the water will "jump" to the copper sulfate from the glass, passing through the air in the form of steam. However, it should be warned that for this experiment it is necessary to move copper sulfate from an aluminum container to a glass one, since wet copper sulfate will actively interact with metallic aluminum:

3CuSO 4 + 2Al → Al 2 (SO 4) 3 + 3Cu

By itself, this reaction will not spoil the picture much. However, it will destroy the Al 2 O 3 protective shell around the aluminum. The latter, in turn, reacts violently with water:

Al + 6H 2 O → Al (OH) 3 + 3H 2

Why may some of the sulfate turn black?

If we overdo it with heating, then we can find another color transition: white copper sulfate darkens.

This is not surprising: we see the beginning of thermal decomposition (decomposition into parts under the influence of temperature) of copper sulfate:

2CuSO 4 → 2CuO + 2SO 2 + O 2

This forms black copper oxide CuO.

To learn more

In chemistry, there is a general rule: if the atoms that make up a solid can form gaseous products, then when heated, it will almost certainly decompose with the formation of these very gases.

For example, the sulfur S and oxygen O atoms of copper sulfate can form gaseous sulfur oxide SO 2 and molecular oxygen O 2. Now let's return to the equation for the reaction of thermal decomposition of copper sulfate: 2CuSO 4 → 2CuO + 2SO 2 + O 2

As we can see, it is these gases that are released if copper sulfate is thoroughly heated.

Experiment development

How to make copper sulfate turn blue again?

In fact, it is very easy! There are several options.

First, you can simply pour the dehydrated sulfate into a plastic container (such as a petri dish) and leave it out in the open. The sulfate will act as a desiccant and gradually absorb water from the air. After a while, it will turn light blue and then blue. This means that the composition of its crystals is again CuSO 4 * 5H 2 O. This option is the simplest, but it has one drawback: the development of the experiment in this way can take several days.

Secondly, you can speed up the process. It is most convenient to use the Petri dish again, but with both parts. Pour all (or part) of the white copper sulfate into a cup. Nearby, at the bottom of the cup, add a couple of drops of water. Make sure that water does not get on the sulfate (otherwise it would be too easy!). Now put the lid on the Petri dish. After a few hours, the sulfate will turn blue again. This time, the transformation takes less time, since we have actually created a "chamber" with excess water vapor inside.

The third way is to add water drop by drop directly to the white copper sulfate. Again, it is most convenient to use a Petri dish, although you can take a regular disposable plastic cup from the Starter Kit as well. Do not add too much water - your task is not to dissolve the copper sulfate, but to saturate it with moisture!

Finally, the fourth option is to dissolve the resulting anhydrous copper sulfate. Do this in a disposable plastic cup. You will receive a blue solution. By the way, if you let the water from this solution slowly evaporate (at room temperature), blue crystals of CuSO 4 * 5H 2 O will form in the glass.

So, there are many ways to bring back the blue color to copper sulfate crystals. The most important thing is that this reaction reversible, which means that you can repeat the experiment over and over again, changing the methods of obtaining blue crystalline copper sulfate hydrate.

It is important to remember that the development of the experiment should not be carried out in an aluminum mold. To find out why, read the answer to the question “What happened? - Is it possible to return the color blue?

What are crystalline hydrates and why are they formed?

Many salts, that is, compounds consisting of positively charged metal ions and a wide variety of negatively charged ions, can form special adducts(from English to add - to add) - hydrates or crystalline hydrates. Essentially, an adduct is a piece that is put together. Many compounds are so named, either for simplicity and convenience, or to show that they are made up of a pair of parts.

In this case, the considered adducts differ from ordinary salts in that they contain water. This water is also called crystallization... Indeed, it is part of the crystal! This usually happens when salts crystallize from aqueous solutions. But why does water remain in the composition of the crystal?

There are two main reasons for this. As you know, compounds readily soluble in water (and these are just many salts) dissociate in it, that is, they decompose into positively and negatively charged ions. So, the first reason is that these ions are in a special environment consisting of water molecules. When the concentration of the solution occurs (in our case, when the water gradually evaporates), these ions come together and form a crystal. At the same time, they often preserve their environment to some extent, actually taking water molecules with them into the crystal.

However, not all salts tend to form hydrates. For example, sodium chloride NaCl always crystallizes without water in its composition, although in solution each ion is surrounded by five to six H2O molecules. Therefore, it is necessary to mention the second reason. Like people, each ion is looking for a more comfortable place. It turns out that in some cases this "comfort" is much better provided by water molecules, and not by "antipode" ions (as is the case with Na + and Cl -). That is, the bonds of ions with water molecules are stronger. This property is more characteristic of positively charged ions, and in most crystalline hydrates, water is located in their environment. This becomes possible due to the electrostatic attraction (the attraction between "+" and "-") between the ions and the water molecule, in which there is a small negative charge on the oxygen atom and a positive charge near the hydrogen atoms.

All crystalline hydrates decompose when heated. At temperatures above 100 o C, water exists in the form of steam. It is under these conditions that water molecules tend to leave the crystalline hydrate.

Copper belongs to the group of seven metals that have been known to man since ancient times. Today, not only copper, but also its compounds are widely used in various industries, agriculture, household and medicine.

The most important copper salt is copper sulfate. The formula of this substance is CuSO4. It is a strong electrolyte and is a white fine crystals, readily soluble in water, odorless and tasteless. The substance is non-flammable and fireproof; when using it, the possibility of spontaneous combustion is completely excluded. Copper sulfate, when exposed to even the smallest amount of moisture from the air, acquires a characteristic blue color with a bright blueness. In this case, the transformation of copper sulfate into the blue pentahydrate CuSO4 5H2O, known as copper sulfate, occurs.

In industry, copper sulfate can be obtained in several ways. One of them, the most common, is the dissolution of waste copper in dilute copper sulfate is obtained in laboratory conditions using a neutralization reaction with sulfuric acid. The formula for the process is as follows: Cu (OH) 2 + H2SO4 → CuSO4 + H2O.

The color-changing property of copper sulfate is used to detect the presence of moisture in organic liquids. With its help, ethanol and other substances are dehydrated in laboratory conditions.

Copper sulfate or, in another way, copper sulfate is widely used in agriculture. Its use, first of all, consists in using a weak solution for spraying plants and dressing cereals before sowing in order to destroy harmful fungal spores. On the basis of copper sulphate, the well-known Bordeaux liquid and milk of lime are made, sold through retail outlets and intended for the treatment of plants from fungal diseases and the destruction of grape aphids.

Copper sulfate is often used in construction. Its use in this area is to neutralize leaks, eliminate rust stains. Also, the substance is used to remove salts from brick, concrete or plastered surfaces. In addition, wood is treated with it as an antiseptic in order to avoid decay processes.

In official medicine, copper sulfate is a drug. It is prescribed by doctors for external use as eye drops, rinsing and douching solutions, and for the treatment of phosphorus burns. As an internal remedy, it is used to irritate the stomach to induce vomiting if necessary.

In addition, mineral paints are made from copper sulfate, it is used in spinning solutions for the manufacture

In the food industry, copper sulphate is registered as food additive E519, used as a color fixer and preservative.

When copper sulphate is sold in retail, it is labeled as a highly hazardous substance. If it enters the human digestive system in an amount of 8 to 30 grams, it can be fatal. Therefore, you should be very careful when using copper sulfate in your home. If the substance comes into contact with the skin or eyes, rinse the area thoroughly with cool running water. If it enters the stomach, it is necessary to make the lavage weak, drink a saline laxative and diuretic.

When working with copper sulfate at home, use rubber gloves and other protective equipment, including a respirator. It is forbidden to use food utensils for the preparation of solutions. After finishing work, be sure to wash your hands and face, and rinse your mouth.