Liquid substances are fluid and take the shape of the container in which they are located. The molecules are located directly next to each other. The liquid in zero gravity will take the form of a round drop.

Water is the only substance that is found on Earth in all three states of aggregation. Water vapor is part of the atmosphere. Solid ice can be seen in the form of snowflakes, in the form of frost, in the form of ice. The World Ocean, surface waters of land and underground waters are filled with liquid water.

Water in the human body Without water, a person can live only 3 days. 82% Water content in the body 79% 75% 72% 70% of an adult: 77% 99% 92% G l o o e t e l a s m a e c l o v i d n p l s t a s a i h e r o v e l s k n c h e p e z a k o tsy we gk le ei rdc s e sh i e i chk poi no in sp g a n e s g a n o m b r e a n z g 46%

The water cycle in nature This is a well-regulated mechanism that continuously “pumps” water from the ocean to the continents and back, while the water is purified. 453,000 km 3 of water evaporates from the surface of the World Ocean annually, and precipitation falling on the Earth is 525,000 km 3. The excess occurs due to the evaporation of water from other water surfaces and the transpiration of moisture by plants.

Water content in nature Water is the most common substance. Earth Water reserves on Earth are 1 million 454 thousand m3, of which 2.8% is fresh water, 0.3% available for use. Volume of water: in the World Ocean 1345 million km 3. on the surface of the Earth 1.39 x 1018 tons. in the atmosphere 1.3 x 1013 tons.

Water consumption Water consumption for production: 1 ton of chemical fiber 2000 m 3 1 ton of paper 900 m 3 1 ton of steel 120 m 3 1 ton of rice 4000 m 3 With such waste, water supplies inexorably dry up. Already, 60% of the entire Earth's surface is occupied by zones suffering from the absence or lack of fresh water.

Water consumption The drinking water requirement of a resident of a large city is about 8 liters per day, and 175 liters of water are consumed daily for all spheres of life. cooking watering plants washing dishes laundry washing flushing the toilet 5% 7% 9% 14% 29% 4 0%

Water hardness is the content of calcium and magnesium ions in water. Disadvantages of hard water: § Soap does not lather § When washing clothes, powder consumption increases § Hair splits § Meat and cereals are poorly cooked. 2 RCOO + Ca 2+ → (RCOO)2 Ca ↓

Crystalline substances Truly solid bodies are crystals, one of the characteristic features of which is the regularity of their appearance.

Crystalline substances General properties: § Preservation of shape and volume. § Presence of a constant melting temperature. § Ordered internal structure. Drusus morion Molten steel

SUBSTANCES only from non-metals ionic cr. decide (Si. O 2; Si. O 2 n. H 2 O) Atomic crystal. decide nonmetals molecular crystal. decide (B, C, Si, Ge, As, Se, Te) simple Atomic crystal. decide metals molecular crystal. decide metal edge decide Crystalline substances complex metal + nonmetal

Crystalline substances aluminum § § § ductility plasticity electrical conductivity thermal conductivity metallic luster SUBSTANCES WITH A METAL CRYSTAL LATTICE

Crystalline substances sulfur naphthalene § § § sugar low hardness low melting temperature volatility SUBSTANCES WITH A MOLECULAR CRYSTAL LATTICE

Crystalline substances C diamond Si. O 2 rock crystal § § hard, durable, refractory, practically insoluble SUBSTANCES WITH AN ATOMIC CRYSTAL LATTICE

Crystalline substances Polymorphism is the existence of different crystal structures in the same substance. Schemes of the structure of various modifications of carbon: a: diamond; b: graphite; c: lonsdaleite; d: fullerene - buckyball C 60; e: fullerene C 540; f: fullerene C 70 g: amorphous carbon, ; h: carbon nanotube

Crystalline substances Anisotropy (from other Greek ἄνισος - unequal and τρόπος - direction) is the dependence of physical properties on the direction inside the crystal. processed mica Anisotropy is more pronounced in single crystals.

Crystalline substances POLYCRYSTALS are solids consisting of a large number of small crystals. Si. O 2 rock crystal (quartz) amethyst (quartz) Isotropy (from other Greek ί σος “equal, identical, similar” + τρόπος “turn; character”) - the same physical properties in all directions.

Crystalline substances ascorbic acid and sucrose vitamin A alloy of titanium and aluminum damask steel Photographs were taken using an electron microscope and nanotechnology.

Crystalline substances MEGACRYSTALS Selenite is a type of gypsum. These crystals are the largest in the world. The largest of them reach a length of 15 m and weigh 50 -60 tons.

Check yourself! When heated, a ball machined from a single crystal can change not only its volume, but also its shape. Why? Answer: Due to anisotropy, crystals expand unevenly when heated.

Check yourself! “The snow creaked underfoot, which means the frost is getting stronger,” you often say. Why does the snow squeak underfoot? Answer: In severe frost, snowflakes do not melt under the weight of feet, but break. Each snowflake makes a very weak, almost imperceptible sound. But if we step on many thousands of snowflakes at once, then barely audible sounds merge into a loud creaking sound.

Check yourself! Why do patterns appear on the surface of galvanized iron over time? Answer: The patterns appear due to the crystallization of zinc.

Amorphous substances (from the Greek amorphos - shapeless, a - negative particle and morphe - form) - can be solid in appearance, but in structure they are liquids.

Amorphous substances § Molecules in amorphous bodies are arranged randomly. § There is no constant melting point; as the temperature rises, they soften. § At low temperatures they behave like crystalline bodies, and at high temperatures they behave like liquids. crystalline structure amorphous structure

Amorphous substances Transition of amorphous bodies into crystalline sulfur plastic sulfur crystalline The amorphous state of substances is unstable, and sooner or later they pass from this state to a crystalline one.

Amorphous substances Transition of amorphous bodies into crystalline chewing gum new used chewing gum The time for the transition of the amorphous state to the crystalline state may vary. For some substances it is several years.

Amorphous substances Transition of amorphous bodies into crystalline ones = Frozen solid honey is candied in the same way as glassy caramel is candied during long-term storage.

polymers Polymers are compounds with high molecular weight, the molecules of which consist of a large number of regularly and irregularly repeating identical or different units. polyvinyl chloride

polymers Depending on the structure of macromolecules, linear, branched (or grafted) and spatial polymers are distinguished. spatial structure linear structure branched structure

polymers Polymers Crystalline Amorphous (crystalline areas less than 25%) (crystalline areas more than 75%) Amorphous-crystalline (crystalline areas 25 -75%)

polymers POLYMERS OF AMORPHOUS STRUCTURE: § with a random mutual arrangement of macromolecules; § have the same physical and mechanical properties in all directions; § characterized by low casting shrinkage, transparency (as a rule), average chemical and wear resistance and high surface friction; § most polymers common in industry are amorphous; § have a BRANCHED molecular structure.

polymers POLYMERS WITH CRYSTAL STRUCTURE: § have an ordered arrangement of macromolecules, their packing density; § have increased heat resistance, high strength, rigidity and density, low elasticity; § capable of deformation, have low surface friction, increased chemical resistance and high shrinkage; § have a LINEAR molecular structure.

polymers LOW PRESSURE POLYETHYLENE Low density polyethylene, in the main chains of which there are numerous branches, can contain up to 70% of the amorphous phase.

polymers AMORPHOUSITY is a valuable quality of polymers, since it determines their technological property as thermoplasticity. Due to its amorphous nature, the polymer can be drawn into the thinnest thread, turned into a transparent film, or cast into a product of the most intricate shape.

Solids / conclusions / “There is nothing absolute in the world except existence or non-existence. Everything else is calculable and relative." Claude Adrian Helvetius

glossary 1. Solids are crystalline substances, one of the characteristic features of which is the regularity of their appearance. 2. Amorphous bodies are bodies that can be solid in appearance, but in structure belong to liquids. 3. Monocrystals - single crystals. 4. Polycrystals are solids consisting of a large number of small crystals. 5. Polymers are compounds with high molecular weight, the molecules of which consist of a large number of regularly and irregularly repeating identical or different units. 6. Amorphous - polymers with less than 25% crystalline areas. 7. Crystalline - polymers with more than 75% crystalline areas. 8. Amorphous-crystalline - polymers with 25-75% crystalline areas. 9. Thermoplasticity - the property of polymers to reversibly harden and soften. 10. Anisotropy is the dependence of physical properties on the direction inside the crystal. 11. Isotropy - the same physical properties in all directions.

As is known, a substance in a liquid state retains its volume, but takes the shape of the vessel in which it is located.

Let's find out how the molecular kinetic theory explains this. The conservation of volume of a liquid proves that attractive forces act between its molecules. Consequently, the distances between liquid molecules must be less than the radius of molecular action.

So, if we describe a sphere of molecular action around a liquid molecule, then inside this sphere there will be the centers of many other molecules that will interact with our molecule. These interaction forces hold the liquid molecule near its temporary equilibrium position for approximately 10 -12 -10 -10 s, after which it jumps to a new temporary equilibrium position approximately the distance of its diameter. Between jumps, the liquid molecules undergo oscillatory motion around a temporary equilibrium position. The time between two jumps of a molecule from one position to another is called time of settled life

. This time depends on the type of liquid and temperature. When a liquid is heated, the average residence time of molecules decreases. During the time of sedentary life (about 10 -11 s), most of the liquid molecules are retained in their equilibrium positions, and only a small part of them manages to move to new equilibrium positions during this time. Therefore, the liquid has fluidity and takes the shape of the vessel in which it is located.

Since the molecules of a liquid are located almost close to each other, then, having received a sufficiently large kinetic energy, although they can overcome the attraction of their nearest neighbors and leave the sphere of their action, they will fall into the sphere of action of other molecules and find themselves in a new temporary equilibrium position. Only molecules located on the free surface of the liquid can fly out of the liquid, which explains the process of its evaporation.

So, if a very small volume is isolated in a liquid, then during the time of settled life there is an ordered arrangement of molecules in it, similar to their arrangement in the crystal lattice of a solid. Then it disintegrates, but arises in another place. Thus, the entire space occupied by the liquid seems to consist of many crystal nuclei, which, however, are unstable, that is, they disintegrate in some places, but arise again in others.

So, in a small volume of liquid there is an ordered arrangement of its molecules, but in a large volume it turns out to be chaotic. In this sense they say that In a liquid, there is short-range order in the arrangement of molecules and no long-range order. This liquid structure is called quasicrystalline(crystal-like). Note that with sufficiently strong heating, the time of settling life becomes very short and short-range order in the liquid practically disappears.

A liquid can exhibit mechanical properties inherent in a solid. If the time of action of the force on the liquid is short, then the liquid exhibits elastic properties. For example, when a stick hits the surface of the water sharply, the stick may fly out of the hand or break; A stone can be thrown so that when it hits the surface of the water it bounces off it, and only after making a few jumps does it sink in the water. If the time of exposure to the liquid is long, then instead of elasticity, fluidity liquids. For example, the hand easily penetrates water.

When a force is applied to a stream of liquid for a short time, the latter detects fragility. The tensile strength of a liquid, although less than that of solids, is not much inferior to them in magnitude. For water it is 2.5 * 10 7 Pa. Compressibility liquid is also very small, although it is larger than that of the same substances in the solid state. For example, when pressure increases by 1 atm, the volume of water decreases by 50 ppm.

Breaks inside a liquid that does not contain foreign substances, for example, air, can only occur under intense influence on the liquid, for example, when propellers rotate in water, or when ultrasonic waves propagate in the liquid. This kind of void inside a liquid cannot exist for a long time and suddenly collapses, i.e., disappears. This phenomenon is called cavitation(from the Greek “cavitas” - cavity). This causes rapid wear of the propellers.

So, liquids have many properties in common with the properties of solids. However, the higher the temperature of a liquid becomes, the more its properties approach the properties of dense gases and the more they differ from the properties of solids. This means that the liquid state is intermediate between the solid and gaseous states of a substance.

Let us also note that when a substance passes from a solid to a liquid state, a less dramatic change in properties occurs than when it passes from liquid to gaseous. This means that, generally speaking, the properties of the liquid state of a substance are closer to the properties of the solid state than to the properties of the gaseous state.

The main property of a liquid, which distinguishes it from other states of aggregation, is the ability to change its shape indefinitely under the influence of tangential mechanical stresses, even arbitrarily small, while practically maintaining its volume. A substance in a liquid state exists in a certain temperature range, below which it turns into a solid state (crystallization occurs or transformation into a solid-state amorphous state - glass), above which it turns into a gaseous state (evaporation occurs). The boundaries of this interval depend on pressure.

3.1Physical properties of liquids:

ü Fluidity(The main property. Unlike plastic solids, a liquid does not have a yield point: it is enough to apply an arbitrarily small external force for the liquid to flow.

ü Volume conservation. One of the characteristic properties of a liquid is that it has a certain volume (under constant external conditions). Liquids are extremely difficult to compress mechanically because, unlike gases, there is very little free space between the molecules. Liquids generally increase in volume (expand) when heated and decrease in volume (contract) when cooled.

ü Viscosity. In addition, liquids (like gases) are characterized by viscosity. It is defined as the ability to resist the movement of one part relative to another - that is, internal friction. When adjacent layers of liquid move relative to each other, collisions of molecules inevitably occur in addition to that caused by thermal motion. The liquid in the vessel, set in motion and left to its own devices, will gradually stop, but its temperature will increase.

ü Free surface formation and surface tension.Due to the conservation of volume, the liquid is able to form a free surface. Such a surface is the interface between the phases of a given substance: on one side there is a liquid phase, on the other - a gaseous (steam) phase. If the liquid and gaseous phases of the same substance come into contact, forces arise that tend to reduce the interface area - surface tension forces . The interface behaves like an elastic membrane that tends to contract.

ü Evaporation and condensation

ü Boiling

ü Wetting- a surface phenomenon that occurs when a liquid comes into contact with a solid surface in the presence of steam, that is, at the interfaces of three phases.

ü Miscibility- the ability of liquids to dissolve in each other. An example of miscible liquids: water and ethyl alcohol, an example of immiscible liquids: water and liquid oil.

ü Diffusion. When there are two mixed liquids in a vessel, the molecules, as a result of thermal movement, begin to gradually pass through the interface, and thus the liquids gradually mix. This phenomenon is called diffusion (also occurs in substances in other states of aggregation).

ü Overheating and hypothermia. A liquid can be heated above its boiling point so that no boiling occurs. This requires uniform heating, without significant temperature changes within the volume and without mechanical influences such as vibration. If you throw something into a superheated liquid, it will instantly boil. Superheated water can easily be obtained in a microwave oven. Supercooling is the cooling of a liquid below its freezing point without turning into a solid state.

1. Liquid state of matter and its properties.

2.1 Bernoulli's law.

2.2 Pascal's law.

2.3 Laminar flow of liquids.

2.4 Poisel's law.

2.5 Turbulent flow of liquids.

3.1 Measurement of liquid viscosity.

3.2 Measurement of volume and flow of liquid

1. Liquid state of matter and its properties.

Liquids occupy an intermediate position between gaseous and solid substances. At temperatures close to boiling points, the properties of liquids approach those of gases; at temperatures close to the melting point, the properties of liquids approach the properties of solids. If solid substances are characterized by a strict ordering of particles, extending over distances of up to hundreds of thousands of interatomic or intermolecular radii, then in a liquid substance there are usually no more than several dozen ordered particles - this is explained by the fact that order between particles in different places of a liquid substance also quickly arises , as again “eroded” by thermal vibration of particles. At the same time, the overall packing density of particles of a liquid substance differs little from that of a solid substance - therefore, their density is close to the density of solids, and their compressibility is very low. For example, to reduce the volume occupied by liquid water by 1%, a pressure of ~200 atm is required, whereas for the same reduction in the volume of gases, a pressure of about 0.01 atm is required. Consequently, the compressibility of liquids is approximately 200: 0.01 = 20,000 times less than the compressibility of gases.

It was noted above that liquids have a certain volume of their own and take the shape of the vessel in which they are located; these properties are much closer to the properties of a solid than a gaseous substance. The closeness of the liquid state to the solid state is also confirmed by data on the standard enthalpies of evaporation ∆Н° isp and the standard enthalpies of melting ∆Н° pl. The standard enthalpy of vaporization is the amount of heat required to convert 1 mole of liquid into vapor at 1 atm (101.3 kPa). The same amount of heat is released when 1 mole of steam condenses into a liquid at 1 atm. The amount of heat consumed to transform 1 mole of a solid into a liquid at 1 atm is called the standard enthalpy of fusion (the same amount of heat is released when 1 mole of liquid “freezes” (“hardens”) at 1 atm). It is known that ∆Н° pl is much less than the corresponding values ​​of ∆Н° isp, which is easy to understand, since the transition from a solid to a liquid state is accompanied by less disruption of intermolecular attraction than the transition from a liquid to a gaseous state.

A number of other important properties of liquids are more similar to the properties of gases. So, like gases, liquids can flow - this property is called fluidity. Resistance to flow is determined by viscosity. Fluidity and viscosity are affected by the attractive forces between liquid molecules, their relative molecular weight, and a number of other factors. The viscosity of liquids is ~100 times greater than that of gases. Just like gases, liquids can diffuse, although much more slowly because liquid particles are packed much more densely than gas particles.

One of the most important properties of a liquid is its surface tension (this property is not inherent in either gases or solids). A molecule in a liquid is uniformly acted on by intermolecular forces from all sides. However, on the surface of the liquid the balance of these forces is disturbed, and as a result, the “surface” molecules find themselves under the influence of a certain resultant force directed into the liquid. For this reason, the surface of the liquid is in a state of tension. Surface tension is the minimum force that restrains the movement of liquid particles into the depth of the liquid and thereby keeps the surface of the liquid from contracting. It is surface tension that explains the “drop-shaped” shape of freely falling liquid particles.

Due to the conservation of volume, the liquid is able to form a free surface. Such a surface is the interface between the phases of a given substance: on one side there is a liquid phase, on the other there is a gaseous phase (steam), and, possibly, other gases, for example, air. If the liquid and gaseous phases of the same substance come into contact, forces arise that tend to reduce the interface area - surface tension forces. The interface behaves like an elastic membrane that tends to contract.

Surface tension can be explained by the attraction between liquid molecules. Each molecule attracts other molecules, strives to “surround” itself with them, and therefore leave the surface. Accordingly, the surface tends to decrease. Therefore, soap bubbles and bubbles tend to take a spherical shape when boiling: for a given volume, a sphere has the minimum surface area. If only surface tension forces act on a liquid, it will necessarily take a spherical shape - for example, water drops in zero gravity.

Small objects with a density greater than that of the liquid are able to “float” on the surface of the liquid, since the force of gravity is less than the force that prevents the increase in surface area.

Wetting is a surface phenomenon that occurs when a liquid comes into contact with a solid surface in the presence of steam, that is, at the interfaces of three phases. Wetting characterizes the “sticking” of a liquid to a surface and spreading over it (or, conversely, repulsion and non-spreading). There are three cases: non-wetting, limited wetting and complete wetting.

Miscibility is the ability of liquids to dissolve in each other. An example of miscible liquids: water and ethyl alcohol, an example of immiscible liquids: water and liquid oil.

When there are two mixed liquids in a vessel, the molecules, as a result of thermal movement, begin to gradually pass through the interface, and thus the liquids gradually mix. This phenomenon is called diffusion (also occurs in substances in other states of aggregation).

A liquid can be heated above its boiling point so that no boiling occurs. This requires uniform heating, without significant temperature changes within the volume and without mechanical influences such as vibration. If you throw something into a superheated liquid, it will instantly boil. Superheated water is easily obtained in the microwave.

Subcooling is the cooling of a liquid below its freezing point without turning into a solid state of aggregation. As with overheating, hypothermia requires the absence of vibration and significant temperature changes.

If you move a section of the liquid surface from the equilibrium position, then under the action of restoring forces the surface begins to move back to the equilibrium position. This movement, however, does not stop, but turns into an oscillatory movement near the equilibrium position and spreads to other areas. This is how waves appear on the surface of the liquid.

If the restoring force is primarily gravity, then such waves are called gravitational waves. Gravitational waves on water can be seen everywhere.

If the restoring force is predominantly the force of surface tension, then such waves are called capillary. If these forces are comparable, such waves are called capillary-gravity waves. Waves on the surface of a liquid are damped under the influence of viscosity and other factors.

Formally speaking, for the equilibrium coexistence of a liquid phase with other phases of the same substance - gaseous or crystalline - strictly defined conditions are required. So, at a given pressure, a strictly defined temperature is needed. However, in nature and in technology everywhere, liquid coexists with steam, or also with a solid state of aggregation - for example, water with steam and often with ice (if we consider steam as a separate phase present along with air). This is due to the following reasons.

Unequilibrium state. It takes time for a liquid to evaporate; until the liquid has completely evaporated, it coexists with steam. In nature, water evaporates constantly, as does the reverse process - condensation.

Closed volume. The liquid in a closed vessel begins to evaporate, but since the volume is limited, the vapor pressure increases, it becomes saturated even before the liquid has completely evaporated, if its quantity was large enough. When the saturation state is reached, the amount of evaporated liquid is equal to the amount of condensed liquid, the system comes into equilibrium. Thus, in a limited volume, the conditions necessary for the equilibrium coexistence of liquid and vapor can be established.

The presence of the atmosphere in conditions of earth's gravity. A liquid is affected by atmospheric pressure (air and steam), while for steam almost only its partial pressure must be taken into account. Therefore, liquid and vapor above its surface correspond to different points on the phase diagram, in the region of existence of the liquid phase and in the region of existence of the gaseous phase, respectively. This does not cancel evaporation, but evaporation requires time during which both phases coexist. Without this condition, the liquids would boil and evaporate very quickly.

2.1 Bernoulli's law - is a consequence of the law of conservation of energy for a stationary flow of an ideal (that is, without internal friction) incompressible fluid:

The attraction and repulsion of particles determine their relative position in matter. And the properties of substances significantly depend on the arrangement of particles. So, looking at a transparent, very hard diamond (diamond) and soft black graphite (pencil leads are made from it), we do not realize that both substances consist of exactly the same carbon atoms. It's just that these atoms are arranged differently in graphite than in diamond.

The interaction of particles of a substance leads to the fact that it can be in three states: hard, liquid And gaseous. For example, ice, water, steam. Any substance can be in three states, but this requires certain conditions: pressure, temperature. For example, oxygen in air is a gas, but when cooled below -193 °C it turns into a liquid, and at -219 °C oxygen is a solid. Iron at normal pressure and room temperature is in a solid state. At temperatures above 1539 °C, iron becomes liquid, and at temperatures above 3050 °C it becomes gaseous. Liquid mercury, used in medical thermometers, becomes solid when cooled below -39 °C. At temperatures above 357 °C, mercury turns into vapor (gas).

By turning metallic silver into a gas, it is sprayed onto glass to create “mirror” glasses.

What properties do substances have in different states?

Let's start with gases, in which the behavior of molecules resembles the movement of bees in a swarm. However, bees in a swarm independently change the direction of movement and practically do not collide with each other. At the same time, for molecules in a gas such collisions are not only inevitable, but occur almost continuously. As a result of collisions, the directions and speeds of the molecules change.

The result of such movement and the lack of interaction between particles during movement is that gas retains neither volume nor shape, but occupies the entire volume provided to it. Each of you will consider the following statements to be sheer absurdity: “Air occupies half the volume of the room” and “I pumped air into two-thirds of the volume of a rubber ball.” Air, like any gas, occupies the entire volume of the room and the entire volume of the ball.

What properties do liquids have? Let's conduct an experiment.

Pour water from one beaker into a beaker of another shape. The shape of the liquid has changed, But volume remained the same. The molecules did not scatter throughout the entire volume, as would be the case with a gas. This means that the mutual attraction of liquid molecules exists, but it does not rigidly hold neighboring molecules. They vibrate and jump from one place to another, which explains the fluidity of liquids.

The strongest interaction is between particles in a solid. It does not allow the particles to disperse. Particles only perform chaotic oscillatory movements around certain positions. That's why solids retain both volume and shape. A rubber ball will retain its ball shape and volume no matter where it is placed: in a jar, on a table, etc.