Lesson “Chemical phenomena. Chemical phenomena in everyday life and everyday life Chemical phenomena in industry

home » Middle Ages Lesson “Chemical phenomena. Chemical phenomena in everyday life and everyday life Chemical phenomena in industry

I. New material

From the course of natural history and physics you know that various changes occur with bodies and substances.

Before you start studying the topic of the lesson, I suggest you complete the following task, take your time with answers, complete the task to the end.

Exercise:

Look carefully at the pictures and try to answer the following questions:

1. Where can you observe the phenomena presented in the drawings and pictures?

№1

№2

№3

№4

№5

№6

2. Give each phenomenon a name. What substances are involved in the phenomena presented? What happens to each substance in the occurring phenomenon? Write down in your workbooks and fill out the following table:

No. Name of the phenomenon	Substance involved in the phenomenon	Changes occurring in the substance
№1,..
…
№6,..

3. In what phenomena are new substances formed?

4. How and by what criteria can the presented phenomena be divided?

Physical and chemical phenomena

By conducting experiments and observations, we are convinced that substances can change.

Changes in substances that do not lead to the formation of new substances (with different properties) are called physical phenomena.

1. Water when heated it can turn into steam, and when cooled - into the ice .

2.Copper wire length changes in summer and winter: increases with heating and decreases with cooling.

3.Volume air in the balloon increases in a warm room.

Changes in substances occurred, but water remained water, copper remained copper, air remained air.

New substances, despite their changes, were not formed.

LET'S ANALYZE THE EXPERIENCE

1. Close the test tube with a stopper with a tube inserted into it

2. Place the end of the tube in a glass of water. We heat the test tube with our hands. The volume of air in it increases, and some of the air from the test tube escapes into a glass of water (air bubbles are released).

3. As the test tube cools, the volume of air decreases and water enters the test tube.

Conclusion. Changes in air volume are a physical phenomenon.

Chemical phenomenon (reaction) – a phenomenon in which new substances are formed.

What signs can be used to determine what happened?chemical reaction ? Some chemical reactions cause precipitation. Other signs are a change in the color of the original substance, a change in its taste, the release of gas, the release or absorption of heat and light.

See examples of such reactions in the table.

Signs of chemical reactions
Change in color of the original substance	Change in taste of the original substance	Precipitation	Gas release	Odor appears

REACTION	SIGN
	COLOR CHANGE
	CHANGES IN TASTE
	GAS EVALUATION

Various chemical reactions constantly occur in living and inanimate nature. Our body is also a real factory of chemical transformations of one substance into another.

Let's observe some chemical reactions.

You cannot conduct experiments with fire yourself!!!

Experience 1

Let's hold a piece of white bread containing organic matter over the fire.

We observe:

1. Charring, that is, a change in color;

2. Odor appears.

Conclusion . A chemical phenomenon has occurred (a new substance has been formed - coal)

Experience 2

Let's cook a glass of starch. Add a little water and mix. Then let's drop iodine solution.

We observe:

1. Sign of reaction: color change (blue discoloration of starch)

Conclusion. A chemical reaction has occurred. The starch has turned into another substance.

Experience 3

1. Dissolve a small amount of baking soda in a glass.

2. Add a few drops of vinegar there (you can take lemon juice or a solution of citric acid).

We are watching:
1. Release of gas bubbles.

Conclusion. The release of gas is one of the signs of a chemical reaction.

Some chemical reactions are accompanied by the release of heat.

Let's sum it up

1. Substances can participate in physical and chemical phenomena

2. Comparative characteristics of physical and chemical phenomena are presented by the following interactive animation

3. Difference between physical and chemical phenomena

·During physical phenomena, the molecules of a substance are not destroyed, the substance is preserved.

· During chemical phenomena, molecules of a substance break down into atoms, and molecules of a new substance are formed from atoms.

Signschemicalreactions

Color change
Precipitation or dissolution of sediment

>> Physical and chemical phenomena (chemical reactions). Let's experiment at home. External effects in chemical reactions

Physical and chemical phenomena (chemical reactions)

The material in this paragraph will help you figure out:

>what is the difference between physical and chemical phenomena.(chemical reactions);
> what external effects accompany chemical reactions.

In natural history lessons, you learned that various physical and chemical phenomena occur in nature.

Physical phenomena.

Each of you has repeatedly observed how ice melts, water boils or freezes. Ice, water and water vapor consist of the same molecules, so they are one substance (in different states of aggregation).

Phenomena in which a substance does not transform into another are called physical.

Physical phenomena include not only changes in substances, but also the glow of hot bodies, the passage of electric current in metals, the spread of the smell of substances in the air, the dissolution of fat in gasoline, and the attraction of iron to a magnet. Such phenomena are studied by the science of physics.

Chemical phenomena (chemical reactions).

One of the chemical phenomena is combustion. Let's consider the process of burning alcohol (Fig. 46). It occurs with the participation of oxygen contained in the air. When burned, alcohol seemingly turns into a gaseous state, just as water turns into steam when heated. But that's not true. If the gas obtained as a result of the combustion of alcohol is cooled, then part of it will condense into liquid, but not into alcohol, but into water. The rest of the gas will remain. With the help of additional experiment it can be proven that this residue is carbon dioxide.

Rice. 46. Burning alcohol

So the alcohol that burns and oxygen, which participates in the combustion process, are converted into water and carbon dioxide.

Phenomena in which some substances are transformed into others are called chemical phenomena or chemical reactions.

Substances that enter into a chemical reaction are called starting substances, or reagents, and those that are formed are called final substances, or reaction products.

The essence of the chemical reaction considered is conveyed by the following entry:

alcohol + oxygen -> water + carbon dioxide
starting materials final substances
(reagents) (reaction products)

The reactants and products of this reaction are made up of molecules. During combustion, a high temperature is created. Under these conditions, the molecules of the reagents disintegrate into atoms, which, when combined, form molecules of new substances - products. Therefore, all atoms are conserved during the reaction.

If the reactants are two ionic substances, then they exchange their ions. Other variants of interaction of substances are also known.

External effects accompanying chemical reactions.

By observing chemical reactions, the following effects can be recorded:

Change in color (Fig. 47, a);
gas release (Fig. 47, b);
formation or disappearance of sediment (Fig. 47, c);
appearance, disappearance or change in odor;
release or absorption of heat;
the appearance of a flame (Fig. 46), sometimes a glow.

Rice. 47. Some external effects during chemical reactions: a - appearance
coloring; b - gas release; c - appearance of sediment

Laboratory experiment No. 3

The appearance of color as a result of the reaction

Are solutions of soda ash and phenolphthalein colored?

Add 2 drops of phenolphthalein solution to a portion of soda solution I-2. What color appeared?

Laboratory experiment No. 4

Release of gas as a result of the reaction

Add a little chloride acid to the soda ash solution. What are you observing?

Laboratory experiment No. 5

The appearance of a precipitate as a result of the reaction

Add 1 ml of copper sulfate solution to the soda ash solution. What's happening?

The appearance of a flame is a sign of a chemical reaction, i.e. it indicates a chemical phenomenon. Other external effects can also be observed during physical phenomena. Let's give a few examples.

Example 1. Silver powder obtained in a test tube as a result of a chemical reaction is gray in color. If you melt it and then cool the melt, you will get a piece of metal, but not gray, but white, with a characteristic shine.

Example 2. If you heat natural water, gas bubbles will begin to emerge from it long before boiling. This is dissolved air; its solubility in water decreases when heated.

Example 3. An unpleasant odor in the refrigerator disappears if granules of silica gel, one of the silicon compounds, are placed in it. Silica gel absorbs molecules of various substances without destroying them. Activated carbon works in a similar way in a gas mask.

Example 4 . When water turns into steam, heat is absorbed, and when water freezes, heat is released.

To determine what kind of transformation has occurred - physical or chemical, you should carefully observe it, as well as comprehensively examine the substances before and after the experiment.

Chemical reactions in nature, everyday life and their significance.

Chemical reactions occur constantly in nature. Substances dissolved in rivers, seas, and oceans interact with each other, some react with oxygen. Plants absorb carbon dioxide from the atmosphere, water and dissolved substances from the soil and process them into proteins, fats, glucose, starch, vitamins, other compounds, as well as oxygen.

This is interesting

As a result of photosynthesis, about 300 billion tons of carbon dioxide are absorbed from the atmosphere each year, 200 billion tons of oxygen are released, and 150 billion tons of organic substances are formed.

Reactions involving oxygen, which enters living organisms during respiration, are very important.

Many chemical reactions accompany us in everyday life. They occur during frying meat, vegetables, baking bread, souring milk, fermenting grape juice, bleaching fabrics, burning various types of fuel, hardening cement and alabaster, blackening silver jewelry over time, etc.

Chemical reactions form the basis of such technological processes as the extraction of metals from ores, the production of fertilizers, plastics, synthetic fibers, medicines, and other important substances. By burning fuel, people provide themselves with heat and electricity. Using chemical reactions, they neutralize toxic substances and process industrial and household waste.

The occurrence of some reactions leads to negative consequences. Rusting of iron shortens the life of various mechanisms, equipment, vehicles, and leads to large losses of this metal. Fires destroy housing, industrial and cultural facilities, and historical values. Most foods spoil due to their interaction with oxygen in the air; in this case, substances are formed that have an unpleasant odor, taste and are harmful to humans.

conclusions

Physical phenomena are the phenomena in which each substance is conserved.

Chemical phenomena, or chemical reactions, are the transformation of one substance into another. They can be accompanied by various external effects.

Many chemical reactions occur in the environment, in plants, animals and humans, and accompany us in everyday life.

?
100. Match:

1) dynamite explosion; a) physical phenomenon;
2) solidification of molten paraffin; b) chemical phenomenon.
3) food burning in a frying pan;
4) the formation of salt during the evaporation of sea water;
5) separation of a strongly shaken mixture of water and vegetable oil;
6) fading of dyed fabric in the sun;
7) passage of electric current in the metal;

101. What external effects are accompanied by such chemical transformations: a) burning of a match; b) rust formation; c) fermentation of grape juice.

102. Why do you think some food products (sugar, starch, vinegar, salt) can be stored indefinitely, while others (cheese, butter, milk) quickly spoil?

Experimenting at home

External effects in chemical reactions

1. Prepare small amounts of aqueous solutions of citric acid and baking soda. Pour portions of both solutions together into a separate glass. What's happening?

Add a few soda crystals to the remainder of the citric acid solution, and a few citric acid crystals to the remainder of the soda solution. What effects do you observe - the same or different?

2. Pour some water into three small glasses and add 1-2 drops of brilliant green alcohol solution, known as “zelenka,” to each. Add a few drops of ammonia to the first glass, and citric acid solution to the second. Has the color of the dye (green) in these glasses changed? If so, how exactly?

Write down the results of the experiments in a notebook and draw conclusions.

Popel P. P., Kryklya L. S., Chemistry: Pidruch. for 7th grade zagalnosvit. navch. closing - K.: VC "Academy", 2008. - 136 p.: ill.

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Unlike physics, chemistry is a science that studies the structure, composition and properties of matter, as well as its changes as a result of chemical reactions. That is, the object of studying chemistry is the chemical composition and its change during a certain process.

Chemistry, like physics, has many sections, each of which studies a specific class of chemical substances, for example, organic and inorganic, bio- and electrochemistry. Research in medicine, biology, geology and even astronomy is based on the achievements of this science.

It is interesting to note that chemistry as a science was not recognized by ancient Greek philosophers due to its experimental focus, as well as the pseudoscientific knowledge that surrounded it (recall that modern chemistry was “born” from alchemy). Only since the Renaissance and largely thanks to the work of the English chemist, physicist and philosopher Robert Boyle, chemistry began to be perceived as a full-fledged science.

Examples of physical phenomena

You can give a huge number of examples that obey physical laws. For example, every schoolchild knows already in the 5th grade a physical phenomenon - the movement of a car on the road. In this case, it does not matter what this car consists of, where it gets energy from to move, the only important thing is that it moves in space (along the road) along a certain trajectory at a certain speed. Moreover, the processes of accelerating and braking a car are also physical. The movement of a car and other solid bodies is dealt with by the section of physics "Mechanics".

Another well-known example of physical phenomena is the melting of ice. Ice, being a solid state of water, at atmospheric pressure can exist for an indefinitely long time at temperatures below 0 o C, but if the ambient temperature is increased by at least a fraction of a degree, or if heat is directly transferred to the ice, for example, by taking it in your hand, then it will start to melt. This process, which occurs with the absorption of heat and a change in the state of aggregation of matter, is an exclusively physical phenomenon.

Other examples of physical phenomena are the floating of bodies in liquids, the rotation of planets in their orbits, electromagnetic radiation of bodies, the refraction of light when crossing the boundary of two different transparent media, the flight of a projectile, the dissolution of sugar in water, and others.

Examples of chemical phenomena

As mentioned above, any processes that occur with a change in the chemical composition of the bodies taking part in them are studied by chemistry. If we return to the example of a car, we can say that the process of burning fuel in its engine is a striking example of a chemical phenomenon, since as a result of it hydrocarbons, interacting with oxygen, lead to the formation of completely different combustion products, the main of which are water and carbon dioxide .

Another striking example of this class of phenomena is the process of photosynthesis in green plants. Initially, they have water, carbon dioxide and sunlight, but after photosynthesis is completed, the initial reagents are no longer there, and glucose and oxygen are formed in their place.

In general, we can say that any living organism is a real chemical reactor, since a huge number of transformation processes take place in it, for example, the breakdown of amino acids and the formation of new proteins from them, the conversion of hydrocarbons into energy for muscle fibers, the process of human respiration, in which hemoglobin binds oxygen, and many others.

One of the amazing examples of chemical phenomena in nature is the cold glow of fireflies, which is the result of the oxidation of a special substance - luciferin.

In the technical field, an example of chemical processes is the production of dyes for clothing and food.

Differences

How do physical phenomena differ from chemical ones? The answer to this question can be understood if we analyze the above information about the objects of study in physics and chemistry. The main difference between them is a change in the chemical composition of the object in question, the presence of which indicates transformations in it, while in the case of unchanged chemical properties of the body they speak of a physical phenomenon. It is important not to confuse a change in chemical composition with a change in structure, which refers to the spatial arrangement of atoms and molecules that form bodies.

Reversibility of physical and irreversibility of chemical phenomena

In some sources, when answering the question of how physical phenomena differ from chemical ones, one can find information that physical phenomena are reversible, but chemical ones are not, however, this is not entirely true.

The direction of any process can be determined using the laws of thermodynamics. These laws say that any process can proceed spontaneously only if its Gibbs energy decreases (internal energy decreases and entropy increases). However, this process can always be reversed by using an external energy source. For example, let's say that scientists recently discovered the reverse process of photosynthesis, which is a chemical phenomenon.

This issue was specifically raised in a separate paragraph, since many people consider combustion to be a chemical phenomenon, but this is not true. However, it would also be wrong to consider the combustion process a physical phenomenon.

The common phenomenon of combustion (bonfire, combustion of fuel in an engine, gas burner or burner, etc.) is a complex physical and chemical process. On the one hand, it is described by a chain of chemical oxidation reactions, but on the other hand, as a result of this process, strong thermal and light electromagnetic radiation occurs, and this is already the field of physics.

Where is the border between physics and chemistry?

Physics and chemistry are two different sciences that have different research methods, while physics can be both theoretical and practical, while chemistry is mainly a practical science. However, in some areas these sciences come into contact so closely that the boundary between them is blurred. Below are examples of scientific fields in which it is difficult to determine “where is physics and where is chemistry”:

quantum mechanics;
nuclear physics;
crystallography;
Materials Science;
nanotechnology.

As can be seen from the list, physics and chemistry closely overlap when the phenomena under consideration are on an atomic scale. Such processes are usually called physicochemical. It is interesting to note that the only person who received the Nobel Prize in Chemistry and Physics at the same time is Marie Skłodowska-Curie.

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Zaporozhye secondary school of І-ІІІ levels No. 90

Chemical phenomena in everyday life and everyday life

7th grade student

Dmitry Baluev

Introduction

chemical reaction fuel oxidation

The world around us, with all its richness and diversity, lives according to laws that are quite easy to explain with the help of sciences such as physics and chemistry. And even the basis of the life activity of such a complex organism as a person is nothing more than chemical phenomena and processes.

Surely, you have often noticed something like how your mother’s silver ring darkens over time. Or how a nail rusts. Or how wooden logs burn to ash. But even if your mother doesn’t like silver, and you’ve never gone camping, you’ve definitely seen how a tea bag is brewed in a cup.

What do all these examples have in common? And the fact that they all relate to chemical phenomena.

So, the most common examples of chemical phenomena in life and everyday life:

rusting nail

fuel combustion

precipitation

grape juice fermentation

rotting paper

synthesis of spirits

darkening of a silver earring

the appearance of a green coating on bronze

scale formation in boilers

extinguishing soda with vinegar

rotting meat

paper burning

Want details? An elementary example is a kettle put on fire. After some time, the water will begin to heat up and then boil. We will hear a characteristic hissing sound, and streams of steam will fly out of the neck of the kettle. Where did it come from, because it wasn’t originally in the dishes! Yes, but water, at a certain temperature, begins to turn into gas, changing its physical state from liquid to gaseous. Those. it remained the same water, only now in the form of steam. This is a physical phenomenon.

And we will see chemical phenomena if we put a bag of tea leaves into boiling water. The water in a glass or other container will turn red-brown. A chemical reaction will occur: under the influence of heat, the tea leaves will begin to steam, releasing the color pigments and flavor properties inherent in this plant. We will get a new substance - a drink with specific qualitative characteristics characteristic only of it. If we add a few spoons of sugar there, it will dissolve (physical reaction), and the tea will become sweet (chemical reaction). Thus, physical and chemical phenomena are often related and interdependent. For example, if the same tea bag is placed in cold water, no reaction will occur, the tea leaves and water will not interact, and the sugar will not want to dissolve either.

Thus, chemical phenomena are those in which some substances are converted into others (water into tea, water into syrup, firewood into ash, etc.) Otherwise, a chemical phenomenon is called a chemical reaction.

We can judge whether chemical phenomena are occurring by certain signs and changes that are observed in a particular body or substance. Thus, most chemical reactions are accompanied by the following “identifying signs”:

as a result or during its occurrence, a precipitate occurs;

the color of the substance changes;

Gases, such as carbon monoxide, may be released during combustion;

heat is absorbed or, conversely, released;

light emission is possible.

For chemical phenomena to be observed, i.e. reactions occur, certain conditions are necessary:

the reacting substances must come into contact, be in contact with each other (i.e. the same tea leaves must be poured into a mug with boiling water);

It is better to grind the substances, then the reaction will proceed faster, interaction will occur sooner (granulated sugar is more likely to dissolve and melt in hot water than lump sugar);

In order for many reactions to occur, it is necessary to change the temperature regime of the reacting components, cooling or heating them to a certain temperature.

You can observe a chemical phenomenon experimentally. But you can describe it on paper using a chemical equation (equation of a chemical reaction).

Some of these conditions also work for the occurrence of physical phenomena, for example, a change in temperature or direct contact of objects and bodies with each other. For example, if you hit the head of a nail hard enough with a hammer, it can become deformed and lose its normal shape. But it will remain the head of a nail. Or, when you turn on the electric lamp, the tungsten filament inside it will begin to heat up and glow. However, the substance from which the thread is made will remain the same tungsten.

But let's look at a few more examples. After all, we all understand that chemistry occurs not only in test tubes in the school laboratory.

1. Chemical phenomena in everyday life

These include those that can be observed in the everyday life of a modern person. Some of them are very simple and obvious; anyone can observe them in their kitchen, like the example of brewing tea.

Using strong (concentrated) tea leaves as an example, you can conduct another experiment yourself: clarify the tea with a slice of lemon. Due to the acids contained in lemon juice, the liquid will once again change its composition.

What other phenomena can you observe in everyday life? For example, chemical phenomena include the process of fuel combustion in an engine.

To simplify, the combustion reaction of fuel in an engine can be described as follows: oxygen + fuel = water + carbon dioxide.

In general, several reactions occur in the chamber of an internal combustion engine, which involve fuel (hydrocarbons), air and an ignition spark. More precisely, not just fuel - a fuel-air mixture of hydrocarbons, oxygen, nitrogen. Before ignition, the mixture is compressed and heated.

The combustion of the mixture occurs in a split second, eventually breaking the bond between the hydrogen and carbon atoms. This releases a large amount of energy, which drives the piston, which then moves the crankshaft.

Subsequently, hydrogen and carbon atoms combine with oxygen atoms to form water and carbon dioxide.

Ideally, the reaction of complete combustion of fuel should look like this: CnH2n+2 + (1.5n+0.5)O2 = nCO2 + (n+1)H2O. In reality, internal combustion engines are not that efficient. Suppose that if there is a slight lack of oxygen during a reaction, CO is formed as a result of the reaction. And with a greater lack of oxygen, soot is formed (C).

The formation of plaque on metals as a result of oxidation (rust on iron, patina on copper, darkening of silver) is also a household chemical phenomenon.

Let's take iron as an example. Rust (oxidation) occurs under the influence of moisture (air humidity, direct contact with water). The result of this process is iron hydroxide Fe2O3 (more precisely, Fe2O3 * H2O). You may see it as a loose, rough, orange or red-brown coating on the surface of metal products.

Another example is a green coating (patina) on the surface of copper and bronze products. It is formed over time under the influence of atmospheric oxygen and humidity: 2Cu + O2 + H2O + CO2 = Cu2CO5H2 (or CuCO3 * Cu(OH)2). The resulting basic copper carbonate is also found in nature - in the form of the mineral malachite.

And another example of a slow oxidation reaction of a metal in everyday conditions is the formation of a dark coating of silver sulfide Ag2S on the surface of silver products: jewelry, cutlery, etc.

“Responsibility” for its occurrence lies with particles of sulfur, which are present in the form of hydrogen sulfide in the air that we breathe. Silver can also darken upon contact with sulfur-containing food products (eggs, for example). The reaction looks like this: 4Ag + 2H2S + O2 = 2Ag2S + 2H2O.

Let's go back to the kitchen. Here you can consider several more interesting chemical phenomena: the formation of scale in a kettle is one of them.

In domestic conditions there is no chemically pure water; metal salts and other substances are always dissolved in it in varying concentrations. If the water is saturated with calcium and magnesium salts (bicarbonates), it is called hard. The higher the salt concentration, the harder the water.

When such water is heated, these salts undergo decomposition into carbon dioxide and insoluble sediment (CaCO3 and MgCO3). You can observe these solid deposits by looking into the kettle (and also by looking at the heating elements of washing machines, dishwashers, and irons).

In addition to calcium and magnesium (which form carbonate scale), iron is also often present in water. During chemical reactions of hydrolysis and oxidation, hydroxides are formed from it.

By the way, when you are about to get rid of scale in a kettle, you can observe another example of entertaining chemistry in everyday life: ordinary table vinegar and citric acid do a good job of removing deposits. A kettle with a solution of vinegar/citric acid and water is boiled, after which the scale disappears.

And without another chemical phenomenon there would be no delicious mother’s pies and buns: we are talking about slaking soda with vinegar.

When mom extinguishes baking soda in a spoon with vinegar, the following reaction occurs: NaHCO3 + CH3COOH = CH3COONa + H2O + CO2. The resulting carbon dioxide tends to leave the dough - and thereby changes its structure, making it porous and loose.

By the way, you can tell your mom that it is not at all necessary to extinguish the soda - she will react anyway when the dough gets into the oven. The reaction, however, will be a little worse than when extinguishing soda. But at a temperature of 60 degrees (or better than 200), soda decomposes into sodium carbonate, water and the same carbon dioxide. True, the taste of ready-made pies and buns may be worse.

The list of household chemical phenomena is no less impressive than the list of such phenomena in nature. Thanks to them, we have roads (making asphalt is a chemical phenomenon), houses (brick firing), beautiful fabrics for clothing (dying). If you think about it, it becomes clearly clear how multifaceted and interesting the science of chemistry is. And how much benefit can be derived from understanding its laws.

2. Interesting chemical phenomena

I would like to add some interesting things. Among the many, many phenomena invented by nature and man, there are special ones that are difficult to describe and explain. This includes burning water. How is this possible, you might ask, since water doesn’t burn, it’s used to extinguish fire? How can it burn? Here's the thing.

Water combustion is a chemical phenomenon in which oxygen-hydrogen bonds are broken in water containing salts under the influence of radio waves. As a result, oxygen and hydrogen are formed. And, of course, it is not the water itself that burns, but hydrogen.

At the same time, it reaches a very high combustion temperature (more than one and a half thousand degrees), plus water is formed again during the reaction.

This phenomenon has long been of interest to scientists who dream of learning how to use water as fuel. For example, for cars. For now, this is something from the realm of science fiction, but who knows what scientists will be able to invent very soon. One of the main snags is that when water burns, more energy is released than is spent on the reaction.

By the way, something similar can be observed in nature. According to one theory, large single waves that seem to appear out of nowhere are actually the result of a hydrogen explosion. Electrolysis of water, which leads to it, is carried out due to the impact of electrical discharges (lightning) on the surface of salt water of the seas and oceans.

But not only in water, but also on land you can observe amazing chemical phenomena. If you had a chance to visit a natural cave, you would probably be able to see bizarre, beautiful natural “icicles” hanging from the ceiling - stalactites. How and why they appear is explained by another interesting chemical phenomenon.

A chemist, looking at a stalactite, sees, of course, not an icicle, but calcium carbonate CaCO3. The basis for its formation is wastewater, natural limestone, and the stalactite itself is built due to the precipitation of calcium carbonate (downward growth) and the force of adhesion of atoms in the crystal lattice (broader growth).

By the way, similar formations can rise from the floor to the ceiling - they are called stalagmites. And if stalactites and stalagmites meet and grow together into solid columns, they are called stalagnates.

Conclusion

There are many amazing, beautiful, as well as dangerous and frightening chemical phenomena happening in the world every day. People have learned to benefit from many things: they create building materials, prepare food, make transport travel great distances, and much more.

Without many chemical phenomena, the existence of life on earth would not be possible: without the ozone layer, people, animals, plants would not survive due to ultraviolet rays. Without plant photosynthesis, animals and people would have nothing to breathe, and without the chemical reactions of respiration, this issue would not be relevant at all.

Fermentation allows you to cook food, and the similar chemical phenomenon of rotting decomposes proteins into simpler compounds and returns them to the cycle of substances in nature.

The formation of an oxide when copper is heated, accompanied by a bright glow, the burning of magnesium, the melting of sugar, etc. are also considered chemical phenomena. And they find useful uses.

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Chemical changes

Chemical changes can be thought of as any phenomenon that allows scientists to measure chemical properties. Many reactions are also examples of chemical phenomena. While it's not always easy to tell that a chemical change has occurred, there are some telltale signs. What are chemical phenomena? Let's give examples. This may be a change in the color of the substance, temperature, the formation of bubbles or (in liquids) the formation of a precipitate. The following examples of chemical phenomena in life can be given:

Rust on iron.
Wood burning.
Metabolism of food in the body.
Mixing acid and alkali.
Cooking the egg.
Digestion of sugar by amylase in saliva.
Mixing baking soda and vinegar to create carbon dioxide gas.
Baking a pie.
Metal galvanization.
Batteries.
Fireworks explosion.
Rotting bananas.
Formation of lactic acid products.

And this is not the entire list. We can look at some of these points in more detail.

Outdoor fire using wood

Fire - this is also an example of a chemical phenomenon. This is the rapid oxidation of a material in an exothermic chemical combustion process, releasing heat, light and various reaction products. The fire is hot because there is a conversion of the weak double bond in molecular oxygen O 2 to the stronger bonds in the combustion products carbon dioxide and water. Great energy is released (418 kJ per 32 g O 2); The binding energies of the fuel play only a minor role here. At a certain point in the combustion reaction, called the flash point, flames are formed.

This is the visible part of fire and consists mainly of carbon dioxide, water vapor, oxygen and nitrogen. If the temperature is high enough, the gases can become ionized to produce plasma. Depending on what substances are ignited and what impurities are supplied from outside, the color of the flame and the intensity of the fire will be different. Fire in its most common form can result in a fire that can cause physical damage when burned. Fire is an important process that affects ecological systems around the world. The positive effects of fire include stimulating growth and maintaining various ecological systems.

Rust

Just like fire, the rusting process is also an oxidative process. Just not as fast-moving. Rust is an iron oxide, usually a red oxide, formed by the redox reaction of iron and oxygen in the presence of water or air. Several forms of rust are distinguished both visually and spectroscopically and form under different circumstances. Given enough time, oxygen and water, any mass of iron will eventually turn completely to rust and decompose. The surface portion is flaky and crumbly, and does not protect the underlying iron, unlike the patina that forms on copper surfaces.

An example of a chemical phenomenon, rusting is a general term for the corrosion of iron and its alloys such as steel. Many other metals undergo similar corrosion, but the resulting oxides are not usually called rust. Other forms of this reaction exist as a result of the reaction between iron and chloride in an oxygen-deprived environment. An example is the rebar used in underwater concrete pillars, which generates green rust.

Crystallization

Another example of a chemical phenomenon is crystal growth. It is a process in which a pre-existing crystal becomes larger as the number of molecules or ions at their positions in the crystal lattice increases. A crystal is defined as atoms, molecules or ions arranged in an ordered repeating pattern, a crystal lattice, extending in all three spatial dimensions. Thus, crystal growth differs from the growth of a liquid drop in that during growth, molecules or ions must fall into the correct lattice positions for an ordered crystal to grow.

When molecules or ions fall into positions different from those in an ideal crystal lattice, crystal defects are formed. Typically, molecules or ions in a crystal lattice are trapped in the sense that they cannot move from their positions, and therefore crystal growth is often irreversible, since once the molecules or ions have fallen into place in the growing lattice, they are fixed in it. Crystallization is a common process in both industry and the natural world, and crystallization is generally understood to consist of two processes. If there was no previously existing crystal, then a new crystal must be born, and then it must undergo growth.

Chemical origin of life

The chemical origin of life refers to the conditions that might have existed and therefore contributed to the emergence of the first duplicated life forms.

The main example of chemical phenomena in nature is life itself. It is believed that a combination of physical and chemical reactions could lead to the appearance of the first molecules, which, through reproduction, led to the emergence of life on the planet.

Conclusion. Changes in air volume are a physical phenomenon.

Examples of physical phenomena

Examples of chemical phenomena

Differences

Reversibility of physical and irreversibility of chemical phenomena

Where is the border between physics and chemistry?

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