Chemical phenomena list. "Physical and chemical phenomena (chemical reactions)

Key words of the synopsis: Physical phenomena, chemical phenomena, chemical reactions, signs of chemical reactions, the meaning of physical and chemical phenomena.

Physical phenomena- these are phenomena in which usually only the state of aggregation of substances changes. Examples of physical phenomena are glass melting, evaporation or freezing of water.

Chemical phenomena- these are phenomena as a result of which other substances are formed from these substances. During chemical phenomena, the original substances are converted into other substances with different properties. Examples of chemical phenomena are combustion of fuel, decay of organic matter, rusting of iron, sour milk.

Chemical phenomena are otherwise called chemical reactions.

Conditions for the occurrence of chemical reactions

The fact that during chemical reactions some substances turn into others can be judged by outward signs: release of heat (sometimes light), discoloration, odor, sediment formation, gas evolution.

For the start of many chemical reactions, it is necessary to lead to close contact reactants ... To do this, they are crushed and mixed; the contact area of the reactants increases. The finest crushing of substances occurs when they are dissolved, therefore, many reactions are carried out in solutions.

Grinding and mixing substances is only one of the conditions for the occurrence of a chemical reaction. For example. when sawdust comes into contact with air at normal temperatures, the sawdust does not ignite. In order for a chemical reaction to begin, in many cases it is necessary to heat the substances to a certain temperature.

Distinguish between concepts "Conditions of occurrence" and "Conditions for the flow of chemical reactions" ... So, for example, in order for combustion to begin, heating is needed only at the beginning, and then the reaction proceeds with the release of heat and light, and further heating is not required. And in the case of decomposition of water, an influx of electrical energy is necessary not only for the start of the reaction, but also for its further course.

The most important conditions for the occurrence of chemical reactions are:

thorough grinding and mixing of substances;
preheating substances to a certain temperature.

The importance of physical and chemical phenomena

Chemical reactions are of great importance. They are used to obtain metals, plastics, mineral fertilizers, medicines, etc., and also serve as a source of various types of energy. So, when fuel is burned, heat is released, which is used in everyday life and in industry.

All vital processes (respiration, digestion, photosynthesis, etc.) occurring in living organisms are also associated with various chemical transformations. For example, chemical transformations of substances contained in food (proteins, fats, carbohydrates) proceed with the release of energy, which is used by the body to support vital processes.

Lesson summary "Physical and chemical phenomena (chemical reactions)".

Often from many people who discuss a particular process, you can hear the words: "This is physics!" or Indeed, practically all phenomena in nature, in everyday life and in space, which a person encounters during his life, can be attributed to one of these sciences. It is interesting to understand how physical phenomena differ from chemical ones.

Science physics

Before answering the question of how physical phenomena differ from chemical ones, it is necessary to understand what objects and processes each of these sciences investigates. Let's start with physics.

From the ancient Greek language, the word "fisis" is translated as "nature". That is, physics is the science of nature, which studies the properties of objects, their behavior in various conditions, transformations between their states. The goal of physics is to determine the laws that govern natural processes that take place. For this science, it does not matter what the object under study consists of, and what is its chemical composition, it is only important for it how the object will behave if it is influenced by heat, mechanical force, pressure, and so on.

Physics is divided into a number of sections that study a certain narrower range of phenomena, for example, optics, mechanics, thermodynamics, atomic physics etc. In addition, many independent sciences depend entirely on physics, for example, astronomy or geology.

Unlike physics, chemistry is a science that studies the structure, composition and properties of matter, as well as its change as a result of chemical reactions. That is, the object of the study of chemistry is the chemical composition and its change in the course of 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 the ancient Greek philosophers because of its orientation towards experiment, as well as because of the pseudoscientific knowledge that surrounded it (recall that modern chemistry was "born" from alchemy). Only from 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

A huge number of examples can be cited that obey physical laws. For example, every student already in the 5th grade knows a physical phenomenon - the movement of a car on the road. At the same time, it does not matter what this car consists of, where it takes energy from to move, it is only important that it moves in space (along the road) along a certain trajectory at a certain speed. Moreover, the processes of acceleration and deceleration of the car are also physical. Vehicle movement and others solids deals with the physics section "Mechanics".

Another well-known one is ice melting. Ice, being a solid state of water, at atmospheric pressure can exist arbitrarily long at temperatures below 0 o C, but if the temperature environment increase by at least a fraction of a degree, or if heat is directly transferred to ice, for example, by taking it in your hand, it will begin to melt. This process, which goes 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, the electromagnetic radiation of bodies, the refraction of light when crossing the border 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 go back to the example of a car, then we can say that the process of burning fuel in its engine is a vivid example of a chemical phenomenon, since as a result of it hydrocarbons, interacting with oxygen, lead to the formation of completely different main ones of which are water and carbon dioxide.

Another striking example of the class of phenomena under consideration is the process of photosynthesis in green plants. Initially, they have water, carbon dioxide and sunlight, after the completion of photosynthesis, 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 is the manufacture of dyes for clothing and food.

Differences

How are physical phenomena different from chemical ones? The answer to this question can be understood if we analyze the above information about the objects of study of physics and chemistry. The main difference between them is a change in the chemical composition of the object under consideration, the presence of which indicates transformations in it, in the case of unchanged chemical properties bodies speak of a physical phenomenon. It is important not to confuse change in chemical composition and a change in structure, which is understood as the spatial arrangement of atoms and molecules that make up 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, and 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 go spontaneously only in the case of a decrease in its Gibbs energy (decrease in internal energy and increase in entropy). However, this process can always be reversed by using an external energy source. For example, let's say that recently scientists discovered the reverse process of photosynthesis, which is a chemical phenomenon.

This question has been specifically raised as a separate item, 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 as a physical phenomenon.

A widespread combustion phenomenon (fire, combustion of fuel in an engine, gas burner or burner, etc.) is a complex physicochemical process. On the one hand, it is described by a chain of chemical reactions of oxidation, but on the other hand, as a result of this process, a 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 touch so closely that the border between them is blurred. The following are examples of scientific industries in which it is difficult to determine "where is physics and where is chemistry":

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

As you can see from the list, physics and chemistry closely overlap when the phenomena in question are on an atomic scale. Such processes are usually called physicochemical. It is curious to note that the only person who received Nobel prize in chemistry and physics at the same time, is Maria Sklodowska-Curie.

Think, answer, do ...

Phenomena	Result	Signs	Examples of
Physical	there is no transformation of some substances into others	change in the state of aggregation of matter	evaporation of water melting ice dissolving salt in water and isolating it again from solution
		changing the shape of an object that is made from a given substance	grinding sugar into icing sugar glass melting melting paraffin making aluminum foil sheet aluminum
Chemical	new substances are formed from these substances	release of heat, light	combustion of fuel ignition of a match
		discoloration	bleaching fabrics with bleach adding lemon to tea
		odor appearance	rotting eggs decomposition of sugar burning food
		sediment formation	turbidity of lime water limescale build-up in the kettle
		gas evolution	extinguishing soda with acetic acid

Examples of phenomena	The significance of these phenomena in human life and activities
1. Physical phenomena
1) water evaporation, water vapor condensation, rainfall	water cycle
2) giving a certain shape to various materials in industrial production	getting a variety of items
2. Chemical phenomena
1) biochemical processes	occur in the organisms of plants, animals, humans
2) fuel combustion	thermal energy production
3) rusting iron	negative value - destruction of iron products
4) interaction of detergents with different kinds pollution	used in everyday life
5) sour milk	obtaining fermented milk products

Conditions for the occurrence and course of chemical reactions

1. Grinding and mixing of substances:

a) for a chemical reaction to begin, sometimes contact of reactants is enough (for example, the interaction of iron with humid air);

b) the more crushed the substances, the larger the surface of their contact with each other, the faster the reaction between them is (for example, a piece of sugar is difficult to ignite, and finely crushed and sprayed in the air sugar burns instantly, with an explosion);

c) facilitates chemical reactions between substances, their preliminary dissolution.

2. Heating substances to a certain temperature. Heating affects the occurrence and course of chemical reactions in different ways:

a) in some cases, heating is required only for the occurrence of a reaction, and then the reaction flows by itself (for example, burning wood and other combustible substances);

b) for other reactions, continuous heating is required, the heating stops - the chemical reaction also stops (for example, the decomposition of sugar).

1. Does not apply to physical phenomena

1) freezing water

2) melting aluminum

3) burning gasoline

4) water evaporation

2. Does not apply to chemical phenomena

1) rusting iron

2) burning food

3) burning gasoline

4) water evaporation

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Class: 8.

Course name: Chemistry .

The purpose of the lesson: the formation of students' ideas about physical and chemical phenomena, signs and conditions of chemical reactions based on the integration of knowledge in physics, biology, life safety.

Lesson Objectives:

Educational:

to form the ability to observe phenomena, recognize them and draw conclusions based on observations;
to form the ability to conduct an experiment in order to respect health;
to form the ability to explain the meaning of phenomena in the life of nature and man;
to study the concepts of "physical phenomena", "chemical phenomena", "signs of chemical reactions", "conditions for the course of reactions";
to show the practical significance of knowledge about chemical phenomena, using intersubject connections.

Educational:

to educate the belief in the cognizability of the chemical component of the picture of the world;
cultivate a respectful attitude towards their health.

Developing:

develop cognitive and communicative activity,
to develop the ability to observe the world around us, to think about its essence, the possibility of influencing the processes taking place around us.

During the lesson, the following are formed and developed competence:

value-semantic (the student's ability to see and understand the world around him);
educational and cognitive (students' skills in the field of independent cognitive activity - the organization of goal-setting, planning, analysis, reflection, self-assessment);
informational (the ability to independently search, analyze, select the necessary information, transform it, etc.)
communicative (skills of working in a group, ways of interacting with people around).

Lesson type: learning new material.

Methods:

reproductive,
partial search,
search.

Equipment and reagents:

on the demonstration table: 4 glasses, a test tube, matches, a candle, a torch, NaHCO 3, CH 3 COOH, H 2 O, NaOH, F.F.
on the students' tables: trays for conducting experiments, a glass slide, a wooden stick, crucible tongs, a mortar, a pestle, a torch, matches, paraffin, CaCO 3, HCI, NaHCO 3, CaCl 2.

Lesson structure:

Motivation.
Goal setting. Updating the knowledge of students from the course of biology, physics and life safety. Creation of a problematic situation.
Experiment as a way of knowing.
Analysis and generalization of the results obtained. Conclusion (definition of a chemical reaction). Expansion of information about a new concept (signs of chemical reactions, conditions for their occurrence).
Anchoring. Reflection.
Estimates. Homework.
Summing up the lesson.

During the classes

Tell me and I will forget.
Show me and I will remember.
Let me do it myself and I'll learn.

(Chinese wisdom)

1. Motivation

Teacher: Hello, today our tutorial will start with a demo. Your attention is invited to observe 2 experiments ( show banks):

1 experience: NaHCO 3 + CH 3 COOH → CH 3 COONa + H 2 O + CO 2 (burning torch)

2 experience: NaHCO 3 + H 2 O →

Question: What did you observe during the reactions?

Answer: 1 experiment - gas is released that does not support combustion, because the burning torch goes out. 2 experiment - dissolving baking soda in water.

Question: What conclusion can be drawn from the results of the experiments performed?

Answer: Changes occurred in 2 experiments.

2. Goal-setting. Updating the knowledge of students from the course of biology, physics and life safety. Creating a problem situation

Teacher(task): Changes are constantly taking place in the world around us, or in another way we call them phenomena. Give examples of natural phenomena that surround us.

Answer:

northern Lights;
snowfall;
hail;
storm;
Rainbow;
fog;
ball lightning;
volcano;
earthquake;
Hurricane;
flood;
flood.

Teacher: Note the "Seasons" pinned to the board (fall, spring).

Question: What happens to substances and bodies?

Answer:

leaf rot: change in the composition of the substance;
change in the color of leaves of trees in autumn: change in the composition of the substance;
melting ice: the substance does not change, only the state of aggregation (from solid to liquid);
the appearance of green in plants under the influence sunlight(photosynthesis)

Teacher: What phenomena do you know from physics (passed the topic: "Changes in the aggregate states of substances")?

Answer:

melting: (w-w) snow melting;
crystallization: (w-t) freezing of water;
vaporization: (g-d) evaporation of water from the ocean surface;
condensation: (ms) dew drop;
sublimation: (t-g) evaporation of naphthalene, melting of graphite, frost;
desublimation: (g-t) patterns on glass.

Question: What happens to substances in the listed phenomena?

Answer: The shape, size, state of aggregation change.

Question: What are these phenomena called?

Answer: Physical.

Teacher: Formulate the topic of our lesson.

Answer: "Phenomena are physical and ...." ( writing to worksheets, Annex 1).

Question: What other phenomena are there besides physical?

Answer: Chemical ( add).

Question: What do we know about them?

Answer: Chemical phenomena are phenomena in which other substances are formed from some substances, therefore they are also called chemical reactions.

Question: What would you like to know about them?

Answer: Learn to identify phenomena, the conditions for their occurrence and course (the purpose of the lesson).

3. Experiment as a way of cognition (group lab / work)

Appendix 2.

Briefing TB (students) and rules for working in groups (teacher) to voice(Appendix 3, 4).

Experience 1. Heating paraffin wax. Apply a few grains of paraffin onto the slide with a wooden stick and, grasping the glass with crucible tongs, gently heat it over the flame of an alcohol lamp.

Experience 2. Grinding chalk. Rub the chalk in a mortar with a pestle.

Experience 3. Interaction of chalk with HCI ( hydrochloric acid). Pour some of the acid dispensed into the test tube and add a little of the ground chalk with a wooden stick. Then, light the splinter and add it to the test tube.

Experience 4. Interaction of solutions NaHCO 3 (baking soda), CaCl 2 (calcium chloride). Pour baking soda solution into a test tube and add some calcium chloride to it. Then, light the splinter and add it to the test tube.

Experimental results

Experience name	Observations (what has changed?)	New substances	Conclusion (what is this phenomenon?)
1. Heating of paraffin.	State of aggregation	Are not formed	Physical
2. Grinding chalk.		Are not formed	Physical
3. Interaction of chalk with acid.	Bubble formation	Formed	Chemical
4. Interaction of solutions of soda and calcium chloride.	Sediment appearance	Formed	Chemical

Self-assessment / assessment by the team captain for the contribution made during the discussion of the conclusions by the group (checking the results against the board).

3 experience: candle burning .

Teacher:

Melo, chalk all over the land
To all limits.
A candle burned on the table
The candle was on fire.
As in the summer we swarm gnats
Flies into the flame
Flakes flew from the yard
To the window frame.
Blizzard sculpted on glass
Circles and arrows.
A candle burned on the table
The candle was on fire.
(B. Pasternak "Winter Night")

What do you see when a candle burns? (changing the shape of the paraffin)
What happens to the substance? (burning) Why? (heating: light and warm)
Why does the glass turn black? (digging is formed - coal.) Where did the water come from on the walls of the glass? (candle combustion product)

Thus, combustion is one of the first reactions mastered by man. For primitive man, fire became a source of heat, a way of protection from wild animals, a means of labor. With its help, people learned to cook food, extract salt, smelt ore. Combustion was the first process that humans learned to control.

4 experience: NaOH with F.F .:

What are you watching? (raspberry color solution)
What does he testify to? (a chemical reaction has occurred).

4. Analysis and generalization of the results obtained. Conclusion (definition of a chemical reaction). Expansion of information about a new concept (signs of chemical reactions, conditions for their occurrence)

Question: So how do you know that a chemical reaction has occurred? (exit to signs of chemical reactions). (Writing in the worksheet).

Answer:

sediment formation (sour milk);
gas evolution;
the release of heat and light;
color change;
the appearance of a smell (sour milk).

Question: What conditions must be met for a reaction to occur?

Answer: (entry in worksheet)

mixing of substances;
heating substances;
action of light.

Question: Why do we need to know the conditions for the occurrence and course of chemical reactions?

Answer: In order to control the course of chemical reactions, sometimes a chemical reaction must be stopped, for example, in the event of a fire, we strive to stop the combustion reaction.

Question (task): What extinguishing agents should be used in the following cases:

the clothes on the man caught fire
gasoline ignited
a forest fire broke out;
ignited oil on the surface of the water.

Question: Thus, what are the main differences between physical and chemical phenomena? Give examples of them.

Answer:

5. Anchoring. Reflection

Exercise 1. Among the phenomena listed below, indicate the chemical phenomena (work in pairs, exchange work for verification):

A). Dissolving sugar in water

B). Decomposition of water by electric current into hydrogen and oxygen

V). Formation of black plaque on silver items

G). Formation of salt crystals upon evaporation of the solution

Task 2. Select the signs of a chemical reaction from the list:

A). Odor

B). The heating

V). Release of gaseous substances

G). Contact of substances

D). Color change

F). Precipitation or dissolution of sediment

H). Good mood

AND). Generation or absorption of heat and / or light

TO). Irradiation with light

L). Communication with each other.

Appendix 5.

6. Estimates. Homework

7. Summing up the lesson

R. Roland (students read out the words): "The lofty goal of a man of science is to penetrate into the very essence of the observed phenomena, to understand their innermost forces, their laws and currents in order to control them."

Students' Choice of Emotional Circle: yellow (excellent), green (good), red

Send your good work in the knowledge base is simple. Use the form below

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Zaporizhzhya comprehensive schoolІ-ІІІ steps No. 90

Chemical phenomena in everyday life and everyday life

Grade 7-A 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 at the heart of the vital activity of such a complex organism as a person is nothing else but 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 does not like silver, and you have never gone on hikes, you saw for sure how a tea bag is brewed in a cup.

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

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

rusting nail

combustion of fuel

precipitation

fermentation of grape juice

rotting paper

synthesis of spirits

darkening silver earring

the appearance of a green bloom on bronze

scale formation in boilers

extinguishing soda with vinegar

rotting meat

burning paper

Want more details? An elementary example is a kettle on fire. After a while, the water will begin to heat up, then boil. We will hear a characteristic hiss, streams of steam will fly out of the neck of the kettle. Where did it come from, because it was not originally in the dishes! Yes, but water, at a certain temperature, begins to turn into gas, changes 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 the chemical phenomena if we put a bag of tea leaves in boiling water. The water in a glass or other container will turn reddish-brown. A chemical reaction will take place: under the influence of heat, the tea leaves will begin to steam, emitting color pigments and flavoring properties inherent in this plant. We will get a new substance - a drink with specific, characteristic only qualitative characteristics. If we add a few tablespoons 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, the reaction will not occur, the tea leaves and water will not interact, and the sugar will not 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 occur by some signs and changes that are observed in a particular body or substance. So, most chemical reactions are accompanied by the following "identification marks":

as a result or during the course of such a precipitate is formed;

there is a change in the color of the substance;

gas may be released, for example carbon monoxide when burning;

there is absorption or, conversely, the release of heat;

light emission possible.

For chemical phenomena to be observed, i.e. reactions took place, some conditions are necessary:

the reacting substances must be in 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 substance, then the reaction will proceed faster, the interaction will sooner occur (granulated sugar will sooner dissolve, melt into hot water than lumpy);

for many reactions to occur, it needs to be changed temperature regime reacting components, cooling or heating them to a certain temperature.

You can observe a chemical phenomenon empirically. But you can describe it on paper using a chemical equation (the 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, bodies with each other. For example, if you hit the nail head hard enough with a hammer, it can deform, lose its usual shape. But it will remain the head of the nail. Or, when you turn on the light bulb in the network, the tungsten filament inside it will start to warm up and glow. However, the substance from which the filament is made will remain the same tungsten.

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

1. Chemical phenomena in everyday life

These include those that can be observed in the daily life of a modern person. Some of them are quite simple and obvious, anyone can observe them in their kitchen, as an example of brewing tea.

Using the example of strong (concentrated) tea brewing, you can independently carry out one more experiment: clarify the tea with the help of a lemon wedge. 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 combustion of fuel 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 take place in the chamber of an internal combustion engine, involving fuel (hydrocarbons), air and an ignition spark. More precisely, not just fuel - a fuel-air mixture of hydrocarbons, oxygen, nitrogen. The mixture is compressed and heated before ignition.

The combustion of the mixture occurs in a split second, as a result, the bond between the hydrogen and carbon atoms is destroyed. Thanks to this, a large number of energy that drives the piston, and that - the crankshaft.

Subsequently, hydrogen and carbon atoms combine with oxygen atoms, water and carbon dioxide are formed.

Ideally, the reaction of complete fuel combustion 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, if oxygen is not enough during the 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 from the category of household chemical phenomena.

Let's take hardware as an example. Rusting (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 loose, rough, orange, or red-brown plaque on the surface of metal products.

Another example is green patina on the surface of copper and bronze products. It forms over time under the influence 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 oxidative reaction of a metal in domestic conditions is the formation of a dark coating of silver sulfide Ag2S on the surface of silver items: jewelry, cutlery, etc.

Particles of sulfur, which are present in the form of hydrogen sulfide in the air we breathe, are "responsible" for its occurrence. Silver can also darken on contact with sulfur-containing foods (eggs, for example). The reaction looks like this: 4Ag + 2H2S + O2 = 2Ag2S + 2H2O.

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

Under domestic conditions, there is no chemically pure water; metal salts and other substances are always dissolved in it in various 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 is.

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

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

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

And without another chemical phenomenon, there would be no tasty mom's pies and buns: we are talking about extinguishing soda with vinegar.

When mom extinguishes 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, makes it porous and friable.

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

The list of everyday 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 burning), beautiful fabrics for clothes (dyeing). If you think about it, it becomes 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. Combustion of water also belongs to them. How is this, perhaps, you ask, because water does not burn, it is used to extinguish fire? How can it burn? Here's the thing.

Combustion of water is a chemical phenomenon in which oxygen-hydrogen bonds are broken in water with an admixture of 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, he achieves a very high temperature combustion (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. While this is something from the realm of fantasy, but who knows what scientists will be able to invent very soon. One of the main snags is that when the 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 lone waves, appearing as if from nowhere, are in fact the result of a hydrogen explosion. The electrolysis of water, which leads to it, is carried out due to the hit of electrical discharges (lightning) on the surface of the salt water of the seas and oceans.

But not only in water, but also on land, one can observe amazing chemical phenomena. If you had a chance to visit a natural cave, you would surely be able to see there 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 education are wastewater, natural limestone, and the stalactite itself is built due to the deposition of calcium carbonate (downward growth) and the cohesion force of atoms in the crystal lattice (breadth growth).

By the way, similar formations can rise from floor to 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, dangerous and frightening chemical phenomena happening in the world every day. From many people have learned to benefit: creates Construction Materials, prepares food, makes vehicles 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 the photosynthesis of plants, 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 a similar chemical phenomenon of putrefaction decomposes proteins into simpler compounds and returns them to the cycle of substances in nature.

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

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Chemical phenomena list. "Physical and chemical phenomena (chemical reactions)

Conditions for the occurrence of chemical reactions

The importance of physical and chemical phenomena

Science physics

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?

During the classes

1. Motivation

2. Goal-setting. Updating the knowledge of students from the course of biology, physics and life safety. Creating a problem situation

3. Experiment as a way of cognition (group lab / work)

4. Analysis and generalization of the results obtained. Conclusion (definition of a chemical reaction). Expansion of information about a new concept (signs of chemical reactions, conditions for their occurrence)

5. Anchoring. Reflection

6. Estimates. Homework

7. Summing up the lesson

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