Properties of transparent bodies. Properties of opaque bodies? Great encyclopedia of oil and gas

What colors belong to the short-wave color group, medium-wave color group, and long-wave color group?

Properties of transparent bodies. Properties of opaque bodies?

Light and color in nature

Light is visible radiation, i.e. electromagnetic waves in the frequency range perceived by the human eye.

Color is one of the properties of the material world, perceived as a conscious visual sensation. This or that color is “assigned” by a person to objects in the process of their visual perception. In the vast majority of cases, the color sensation arises as a result of exposure of the eye to streams of electromagnetic radiation from the wavelength range in which this radiation is perceived by the eye (visible range - wavelengths from 380 to 760 nm).

The flow of radiant energy, falling on the surface, partially penetrates deep into the body and fades as it penetrates into the thickness, and is partially reflected from the surface. The degree of extinction depends on the characteristics of the radiation flux and the properties of the body in which the process occurs. In this case, they say that the surface absorbs the rays.

Depending on the distance to which the light beam penetrates deep into the body before complete extinction, All bodies are conventionally divided into transparent, translucent and opaque. Only vacuum is considered absolutely transparent to all rays. Transparent bodies include air, water, glass, crystal, and some types of plastics. Metals are generally considered opaque. Porcelain, frosted glass - translucent bodies.

A substance or medium is called “transparent” if objects can be seen through this substance or medium; in this sense, a transparent substance is called, therefore, one that transmits, without absorbing or scattering, rays of all or some wavelengths acting on the retina of the eye. If a substance freely transmits all or almost all the rays of the spectrum visible to the eye, such as water, glass, quartz, then it is called “completely transparent”; if only some rays of the spectrum pass freely, while others are absorbed, then such a medium is called “transparent colored”, since, depending on the rays transmitted by the medium, objects viewed through it appear to be colored in one color or another; such as, for example, colored glass, a solution of copper sulfate, etc. It is possible, by appropriate treatment, to change the degree of radiation of the medium without changing the nature of the rays transmitted by it; so, for example, by making the surface of a glass plate matte, that is, by covering it with a network of small irregular edges that reflect and scatter light, one can prepare a “translucent” plate through which the outlines of objects will be barely visible; By adding to a transparent medium a fine powder of a substance of a different refractive index suspended in it (milk glass, emulsions) or by soaking an almost opaque substance with liquid (paper impregnated with oil; mineral hydrophane impregnated with water), we obtain a “translucent” medium through which no The contours of objects are already visible, but the presence of light sources also differs. The power of a medium is thus determined primarily by the amount of light rays absorbed and scattered when passing through the medium; the latter depends on the thickness of the medium, increasing as the thickness of the path traveled by the rays increases.

Very thin layers of opaque substances (thin layers of metals) transmit some amount of light, but thick layers of even very transparent bodies (water) can be opaque. The absorption coefficient for a given substance depends on the wavelength of the transmitted light and for rays of different wavelengths for the same substance can be very different.

Bodies can be transparent or opaque. Reflection, absorption, transmission - can only occur when transparent objects are illuminated. A certain color of an object is fixed by the eye after the interaction of light with this object, depending on the wavelength of the reflected color.

This is how a white sheet looks white because it reflects all the colors. A green object reflects predominantly green rays, a blue object reflects blue rays. If an object absorbs all the light falling on it, then it is perceived as black

The air environment retains and scatters some of the violet, blue, cyan rays, transmitting the rest almost without interference. Hence the result - a blue sky above our head. Morning and evening dawns are painted in warm colors, since sunlight, breaking through a thicker layer of the atmosphere, loses many cold rays. And the snow on the tops of mountains illuminated by the sun appears pinkish, due to the fact that the bright light reflected by the white surface also loses some of the short-wave (cold) rays on its way to us.

Reflection of rays. A ray of light falling on a smooth surface is reflected from it at the same angle, i.e. The angle of incidence of the beam is equal to the angle of its reflection. Based on the nature of the reflection of light rays, surfaces are divided into mirror, glossy and matte.

Mirror surfaces reflect almost the entire beam flux at the same angle to the surface without scattering it.

Glossy surfaces, such as those painted with enamel paints, reflect a significant portion of the rays in a direction close to specular, somewhat scattering them. An example of this kind of surfaces are surfaces painted with enamel paints.

Matte surfaces scatter light rays as a result of some roughness (for example, fresh dried plaster, a wall coated with adhesive paint, unpainted wood).

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The transparent substance is divided into amorphous and crystalline according to its structure. Part of the amorphous material is a binding substance between transparent and opaque crystals or is presented in the form of grains with a diameter of 4 - 120 microns. Balls of smaller diameters are usually homogeneous, while larger ones are amorphous or amorphous with crystalline inclusions. The majority of amorphous balls are colorless or brownish-yellow or black. Black balls are often surrounded by a crystalline halo 1 - 2 μm wide or surrounded by crystalline shells. Taking into account the obtained N values, it can be assumed that the amorphous substance consists mainly of a glassy mass of various chemical compositions.  

A transparent substance, such as a sheet of window glass, must also contain a certain amount of absorbent inclusions, since there is a slight attenuation of the light intensity when such a sheet is placed in the path of light rays. In addition, the glass heats up a little.  

Non-black transparent substances transmit part of the radiation incident on them. Let us define the transmittance coefficients Tv and m as the fractions of the spectral and total energy, respectively, that are transmitted by the substance.  

Diamond is a colorless, transparent substance that refracts light rays extremely strongly. It crystallizes in a face-centered cubic lattice. In this case, one half of the atoms is located at the vertices and centers of the faces of one cube, and the other - at the vertices and centers of the faces of another cube, displaced relative to the first in the direction of its spatial diagonal. The distance between atoms in tetrahedra is 0 154 nm.  

Transparent substances for electromagnetic waves are dielectrics, whose magnetic properties depend very little on their type, so their relative magnetic permeability can be taken as unity.  

Transparent substances for electromagnetic waves are dielectrics, whose magnetic properties depend very little on their type, so their relative magnetic permeability can be taken equal to unity.  

Many transparent substances, which are characterized by a lack of symmetry in their molecular or crystalline structure, have the ability to rotate the plane of polarized radiation. Such substances are called optically active.  

Many transparent substances, which are characterized by a lack of symmetry in the molecular or crystal structure, are capable of rotating the plane of polarized radiation (brief information about the nature of plane-polarized radiation is given in Chapter. Such substances are called optically active. The angle of rotation of the plane of polarization varies widely from one optically active compound to another. The degree of rotation depends on the number of molecules in the path of radiation or for solutions, on their concentration and the length of the vessel, as well as on the wavelength of the radiation and temperature.  

Each transparent substance has its own absorption spectrum. If a transparent substance uniformly absorbs rays of all colors, then in transmitted light, when illuminated by white light, it is colorless, and when illuminated with color, it has the color of the rays by which it is illuminated. With very strong absorption of rays of all colors, the body appears black to us. When a body has selective absorption, then when illuminated by rays of one of the colors that it transmits, the body is painted in the same color.  

Many transparent substances, characterized by a lack of symmetry in their molecular or crystal structure, have the ability to rotate the plane of polarized radiation. Such substances are called optically active. The most famous of them are quartz and sugar. However, many organic and inorganic compounds also have this property. The angle of rotation of the plane of polarization varies over a wide range for different substances. Rotation is called right () if it occurs in the direction of clockwise movement for an observer looking towards the light beam, and left (-) if it occurs counterclockwise. For any complex substance, the angle of rotation depends on the number of molecules located in the path of the light beam or, in the case of a solution, on the concentration of the latter and the length of the vessel. It also depends on the radiation wavelength and temperature.  

When studying the material in the previous paragraphs, you have already become acquainted with some substances. For example, a molecule of hydrogen gas consists of two atoms of the chemical element hydrogen - H + H = H2.

Simple substances are substances that contain atoms of the same type

Simple substances known to you include: oxygen, graphite, sulfur, nitrogen, all metals: iron, copper, aluminum, gold, etc. Sulfur consists only of atoms of the chemical element sulfur, while graphite consists of atoms of the chemical element carbon.

It is necessary to clearly distinguish between concepts "chemical element" And "simple matter". For example, diamond and carbon are not the same thing. Carbon is a chemical element, and diamond is a simple substance formed by the chemical element carbon. In this case, the chemical element (carbon) and the simple substance (diamond) are called differently. Often a chemical element and its corresponding simple substance are named the same. For example, the element oxygen corresponds to a simple substance - oxygen.

It is necessary to learn how to distinguish between where we are talking about an element and where about a substance! For example, when they say that oxygen is part of water, we are talking about the element oxygen. When they say that oxygen is a gas necessary for breathing, we are talking about the simple substance oxygen.

Simple substances of chemical elements are divided into two groups - metals and non-metals.

Metals and non-metals radically different in their physical properties. All metals are solid substances under normal conditions, with the exception of mercury - the only liquid metal. Metals are opaque and have a characteristic metallic luster. Metals are ductile and conduct heat and electricity well.

Nonmetals are not similar to each other in physical properties. So, hydrogen, oxygen, nitrogen are gases, silicon, sulfur, phosphorus are solids. The only liquid non-metal is bromine, a brownish-red liquid.

If you draw a conventional line from the chemical element boron to the chemical element astatine, then in the long version of the Periodic System there are non-metallic elements above the line, and below it - metal. In the short version of the Periodic Table, there are non-metallic elements below this line, and both metallic and non-metallic elements above it. This means that it is more convenient to determine whether an element is metallic or non-metallic using the long version of the Periodic Table. This division is arbitrary, since all elements in one way or another exhibit both metallic and non-metallic properties, but in most cases this distribution corresponds to reality.

Complex substances and their classification

If the composition of simple substances includes atoms of only one type, it is easy to guess that the composition of complex substances will include several types of different atoms, at least two. An example of a complex substance is water; you know its chemical formula - H2O. Water molecules are made up of two types of atoms: hydrogen and oxygen.

Complex substances- substances containing atoms of various types

Let's conduct the following experiment. Mix sulfur and zinc powders. Place the mixture on a metal sheet and set it on fire using a wooden torch. The mixture ignites and quickly burns with a bright flame. After the completion of the chemical reaction, a new substance was formed, which included sulfur and zinc atoms. The properties of this substance are completely different from the properties of the starting substances - sulfur and zinc.

Complex substances are usually divided into two groups: inorganic substances and their derivatives and organic substances and their derivatives. For example, rock salt is an inorganic substance, and the starch contained in potatoes is an organic substance.

Types of structure of substances

Based on the type of particles that make up the substances, substances are divided into substances molecular and non-molecular structure.

The substance may contain various structural particles, such as atoms, molecules, ions. Consequently, there are three types of substances: substances of atomic, ionic and molecular structure. Substances of different types of structure will have different properties.

Substances of atomic structure

An example of substances of atomic structure are substances formed by the element carbon: graphite and diamond. These substances contain only carbon atoms, but the properties of these substances are very different. Graphite– a fragile, easily exfoliating substance of gray-black color. Diamond– transparent, one of the hardest minerals on the planet. Why do substances consisting of the same type of atom have different properties? It's all about the structure of these substances. The carbon atoms in graphite and diamond join together in different ways. Substances of atomic structure have high boiling and melting points, are usually insoluble in water, and nonvolatile.

Crystal lattice – an auxiliary geometric image introduced to analyze the structure of a crystal

Substances of molecular structure

Substances of molecular structure– These are almost all liquids and most gaseous substances. There are also crystalline substances whose crystal lattice includes molecules. Water is a substance of molecular structure. Ice also has a molecular structure, but unlike liquid water, it has a crystal lattice where all molecules are strictly ordered. Substances of molecular structure have low boiling and melting points, are usually fragile, and do not conduct electricity.

Substances of ionic structure

Substances of ionic structure are solid crystalline substances. An example of an ionic compound substance is table salt. Its chemical formula is NaCl. As we can see, NaCl consists of ions Na+ and Cl⎺, alternating in certain places (nodes) of the crystal lattice. Substances with an ionic structure have high melting and boiling points, are fragile, are usually highly soluble in water, and do not conduct electric current.

The concepts of “atom”, “chemical element” and “simple substance” should not be confused.

• "Atom"– a specific concept, since atoms really exist.
• "Chemical element"– is a collective, abstract concept; In nature, a chemical element exists in the form of free or chemically bonded atoms, that is, simple and complex substances.

The names of chemical elements and the corresponding simple substances are the same in most cases.

When we talk about a material or component of a mixture - for example, a flask is filled with chlorine gas, an aqueous solution of bromine, let's take a piece of phosphorus - we are talking about a simple substance. If we say that a chlorine atom contains 17 electrons, the substance contains phosphorus, the molecule consists of two bromine atoms, then we mean a chemical element.

It is necessary to distinguish between the properties (characteristics) of a simple substance (a collection of particles) and the properties (characteristics) of a chemical element (an isolated atom of a certain type), see the table below:

Complex substances must be distinguished from mixtures, which also consist of different elements.

The quantitative ratio of the components of the mixture can be variable, but the chemical compounds have a constant composition.

For example, in a glass of tea you can add one spoon of sugar, or several, and sucrose molecules С12Н22О11 contains exactly 12 carbon atoms, 22 hydrogen atoms and 11 oxygen atoms.

Thus, the composition of compounds can be described by one chemical formula, and the composition no mixture.

The components of the mixture retain their physical and chemical properties. For example, if you mix iron powder with sulfur, a mixture of two substances is formed. Both sulfur and iron in this mixture retain their properties: iron is attracted by a magnet, and sulfur is not wetted by water and floats on its surface.

If sulfur and iron react with each other, a new compound is formed with the formula FeS, which does not have the properties of either iron or sulfur, but has a set of its own properties. In connection FeS iron and sulfur are bound to each other, and it is impossible to separate them using the methods used to separate mixtures.

Thus, substances can be classified according to several parameters:

Conclusions from an article on the topic Simple and complex substances

• Simple substances- substances that contain atoms of the same type
• Simple substances are divided into metals and non-metals
• Complex substances- substances containing atoms of various types
• Complex substances are divided into organic and inorganic
• There are substances of atomic, molecular and ionic structure, their properties are different
• Crystal cell– an auxiliary geometric image introduced to analyze the crystal structure

7. Hypnotic bromic acid

Your dealer is out of town and you're missing your daily dose of LSD? No problem. All you need is two simple substances and a Petri dish to create not a virtual, but a real lava lamp with your own hands. Just a joke, otherwise they’ll come and close the site...

According to science, the Belousov-Zhabotinsky reaction is an “oscillatory chemical reaction” during which “transition group metal ions catalyze the oxidation of various, usually organic, reducing agents with bromic acid in an acidic aqueous medium,” which allows “the formation of complex spatio-temporal structures to be observed with the naked eye.” structures." This is the scientific explanation for the hypnotic phenomenon that occurs when you throw a little bromine into an acidic solution.

The acid turns the bromine into a chemical called bromide (which takes on a completely different color), and the bromide quickly turns back into bromine because the science elves living inside it are stubborn assholes. The reaction repeats over and over again, allowing you to endlessly watch the movement of incredible wave-like structures.

6. Clear Chemicals Turn Black Instantly

Question: What happens if you mix sodium sulfite, citric acid and sodium iodide? The correct answer is below:

When you mix the above ingredients in certain proportions, the end result is a capricious liquid that starts out clear in color and then suddenly turns black. This experiment is called the Iodine Clock. Simply put, this reaction occurs when specific components combine in such a way that their concentration gradually changes. If it reaches a certain threshold, the liquid turns black.
But that is not all. By changing the proportion of ingredients, you have the opportunity to get the opposite reaction:

In addition, using various substances and formulas (for example, the Briggs-Rauscher reaction, as an option), you can create a schizophrenic mixture that will constantly change its color from yellow to blue.

5. Creating plasma in the microwave

Do you want to do something fun with your friend, but you don't have access to a bunch of obscure chemicals or the basic knowledge needed to mix them safely? Don't despair! All you need for this experiment are grapes, a knife, a glass and a microwave. So, take a grape and cut it in half. Divide one of the pieces into two parts again with a knife so that these quarters remain connected by the peel. Place them in the microwave and cover with an upside down glass, turn on the oven. Then step back and watch as the aliens steal the cut berry.

In fact, what is happening before your eyes is one of the ways to create a very small amount of plasma. Since school, you know that there are three states of matter: solid, liquid and gas. Plasma is essentially the fourth type and is an ionized gas obtained by superheating ordinary gas. Grape juice turns out to be rich in ions, and therefore is one of the best and most affordable means for conducting simple scientific experiments.

However, be careful when trying to create a plasma in the microwave, as the ozone that forms inside the glass can be toxic in large quantities!

4. Laminar flow

If you mix coffee with milk, you will end up with a liquid that you are unlikely to ever be able to separate into its constituent components again. And this applies to all substances that are in a liquid state, right? Right. But there is such a thing as laminar flow. To see this magic in action, just place a few drops of multi-colored dyes in a transparent container with corn syrup and mix everything carefully...

... and then mix again at the same pace, but now in the opposite direction.

Laminar flow can occur under any conditions and using different types of liquids, but in this case, this unusual phenomenon is due to the viscous properties of corn syrup, which, when mixed with dyes, forms multi-colored layers. So, if you just as carefully and slowly perform the action in the opposite direction, everything will return to its original place. It's like traveling back in time!

3. Lighting an extinguished candle through a trail of smoke

You can try this trick at home without the risk of exploding your living room or the entire house. Light a candle. Blow it out and immediately bring the fire to the smoke trail. Congratulations: you did it, now you are a true master of fire.

It turns out that there is some kind of love between fire and candle wax. And this feeling is much stronger than you think. It doesn’t matter what state the wax is in - liquid, solid, gaseous - the fire will still find it, overtake it and burn it to hell.

2. Crystals that glow when crushed

Here is a chemical called europium tetrakis, which exhibits the effect of triboluminescence. However, it is better to see once than to read a hundred times.

This effect occurs when crystalline bodies are destroyed due to the conversion of kinetic energy directly into light.

If you want to see all this with your own eyes, but you don’t have europium tetrakis on hand, it doesn’t matter: even the most ordinary sugar will do. Just sit in a dark room, put a few sugar cubes in a blender and enjoy the beauty of fireworks.

Back in the 18th century, when many people thought that scientific phenomena were caused by ghosts or witches or ghosts of witches, scientists used this effect to make fun of “mere mortals” by chewing sugar in the dark and laughing at those who fled from them like fire .

1. A hellish monster emerging from a volcano

Mercury(II) thiocyanate is a seemingly innocent white powder, but once you set it on fire, it immediately turns into a mythical monster, ready to devour you and the whole world.

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