The molecular-kinetic theory of the structure of matter is based on three statements:
- matter is made up of particles;
- particles move randomly;
- particles interact with each other.
Each assertion is rigorously proven by experiments.
The volume V of the oil layer is equal to the product of its surface area S and the thickness d of the layer, i.e. V=S*d/ Therefore, the size of an olive oil molecule is equal to:
The diameter of a water molecule is approximately 3 10 cm . Assuming that each water molecule in densely packed molecules occupies a volume of approximately 3*10 8 cm 3 , you can find the number of molecules in a drop by dividing the volume of the drop 1 cm 3 per volume per molecule:
MASS OF MOLECULES. QUANTITY OF SUBSTANCE.
The mass of atoms and molecules differ significantly. What quantities are convenient to characterize them? How to determine the number of atoms in any macroscopic body?
A new quantity appears - the amount of matter.
The mass of a water molecule. The masses of individual molecules and atoms are very small. For example, in 1 g water contains 3.7 * 10 22 molecules. Therefore, the mass of one water molecule (H 2 O) is:
Since the masses of molecules are very small, it is convenient to use in calculations not the absolute values of the masses, but relative ones. By international agreement, the masses of all atoms and molecules are compared with the masses of a carbon atom (the so-called carbon scale of atomic masses).
The relative molecular (or atomic) mass of the substance M r . call the ratio of the mass of a molecule (or atom) m 0 of a given substance to the mass of a carbon atom m os:
Amount of substance the most natural would be to measure it by the number of molecules or atoms in the body. But the number of molecules in any macroscopic body is so great that the calculations do not use the absolute number of molecules, but the relative one.
In the International System of Units, the amount of a substance is expressed in moles.
One mole is the amount of a substance that contains as many molecules or atoms as there are atoms in 0.012 kg of carbon.
This means that 1 mole of any substance contains the same number of atoms or molecules. This number of atoms is N A and is called the Avogadro constant in honor of the Italian scientist (nineteenth century).
N A - Avogadro constant.
To determine the Avogadro constant, you need to find the mass of one carbon atom. A rough estimate of the mass can be made in the same way as was done above for the mass of the water molecule (the most accurate methods are based on the deflection of ion beams by an electromagnetic field).
Explanation of Brownian motion.
Brownian motion can be explained only on the basis of molecular-kinetic theory. The reason for the Brownian motion of a particle is that the impacts of liquid molecules on the particle do not cancel each other out. When molecules move randomly, the impulses they transmit to a Brownian particle, for example, from the left and right, are not the same, therefore the resulting pressure force of the liquid molecules on the Brownian particle is nonzero, which causes a change in its motion.
gases are easily compressed, thus reducing the average distance
between molecules, but the molecules do not squeeze each other. The volume of the vessel is tens of thousands of times greater than the volume of
him molecules. Gases are easily compressed this reduces the average distance between the molecules, but the molecules do not squeeze each other.
Molecules with huge speeds - hundreds of meters per second - move in space. Colliding, they bounce off each other in different directions like billiard balls. Weak forces of attraction of gas molecules are not able to keep them near each other. So gases can expand indefinitely. They retain neither shape nor volume. Numerous impacts of molecules on the walls of the vessel create gas pressure.
Molecular-kinetic theory is a branch of physics that studies the properties of various states of matter, based on the concept of the existence of molecules and atoms as the smallest particles of matter. The ICT is based on three main principles:
1. All substances consist of the smallest particles: molecules, atoms or ions.
2. These particles are in continuous chaotic motion, the speed of which determines the temperature of the substance.
3. Between the particles there are forces of attraction and repulsion, the nature of which depends on the distance between them.
The main provisions of the MKT are confirmed by many experimental facts. The existence of molecules, atoms and ions has been proven experimentally, molecules have been sufficiently studied and even photographed using electron microscopes. The ability of gases to expand indefinitely and occupy the entire volume provided to them is explained by the continuous chaotic movement of molecules. The elasticity of gases, solids and liquids, the ability of liquids to wet some solids, the processes of coloring, gluing, maintaining the shape of solids, and much more indicate the existence of forces of attraction and repulsion between molecules. The phenomenon of diffusion - the ability of the molecules of one substance to penetrate into the gaps between the molecules of another - also confirms the basic provisions of the MKT. The phenomenon of diffusion explains, for example, the spread of odors, the mixing of dissimilar liquids, the process of dissolving solids in liquids, the welding of metals by melting them or by pressure. A confirmation of the continuous chaotic motion of molecules is also Brownian motion - the continuous chaotic motion of microscopic particles that are insoluble in a liquid.
The movement of Brownian particles is explained by the chaotic movement of fluid particles that collide with microscopic particles and set them in motion. It has been experimentally proved that the speed of Brownian particles depends on the temperature of the liquid. The theory of Brownian motion was developed by A. Einstein. The laws of motion of particles are of a statistical, probabilistic nature. There is only one known way to reduce the intensity of Brownian motion - a decrease in temperature. The existence of Brownian motion convincingly confirms the motion of molecules.
Any substance consists of particles, therefore the amount of substance v is considered to be proportional to the number of particles, i.e. structural elements contained in the body.
The unit of quantity of a substance is the mole. A mole is the amount of a substance that contains as many structural elements of any substance as there are atoms in 12 g of C12 carbon. The ratio of the number of molecules of a substance to the amount of a substance is called the Avogadro constant:
The Avogadro constant shows how many atoms and molecules are contained in one mole of a substance. Molar mass - the mass of one mole of a substance, equal to the ratio of the mass of the substance to the amount of the substance:
Molar mass is expressed in kg/mol. Knowing the molar mass, you can calculate the mass of one molecule:
The average mass of molecules is usually determined by chemical methods, the Avogadro constant has been determined with high accuracy by several physical methods. The masses of molecules and atoms are determined with a considerable degree of accuracy using a mass spectrograph.
The masses of molecules are very small. For example, the mass of a water molecule:
The molar mass is related to the relative molecular mass Mg. Relative molecular weight is a value equal to the ratio of the mass of a molecule of a given substance to 1/12 of the mass of a C12 carbon atom. If the chemical formula of a substance is known, then its relative mass can be determined using the periodic table, which, when expressed in kilograms, shows the magnitude of the molar mass of this substance.
Experimental substantiation of the main provisions of the molecular-kinetic theory (MKT) of the structure of matter. Mass and size of molecules. Avogadro constant.Molecular-kinetic theory is a branch of physics that studies the properties of various states of matter, based on the concept of the existence of molecules and atoms as the smallest particles of matter. The ICT is based on three main principles:
1. All substances consist of the smallest particles: molecules, atoms or ions.
2. These particles are in continuous chaotic motion, the speed of which determines the temperature of the substance.
3. Between the particles there are forces of attraction and repulsion, the nature of which depends on the distance between them.
The main provisions of the MKT are confirmed by many experimental facts. The existence of molecules, atoms and ions has been proven experimentally, molecules have been sufficiently studied and even photographed using electron microscopes. The ability of gases to expand indefinitely and occupy the entire volume provided to them is explained by the continuous chaotic movement of molecules. The elasticity of gases, solids and liquids, the ability of liquids to wet some solids, the processes of coloring, gluing, maintaining the shape of solids, and much more indicate the existence of forces of attraction and repulsion between molecules. The phenomenon of diffusion - the ability of the molecules of one substance to penetrate into the gaps between the molecules of another - also confirms the basic provisions of the MKT. The phenomenon of diffusion explains, for example, the spread of odors, the mixing of dissimilar liquids, the process of dissolving solids in liquids, the welding of metals by melting them or by pressure. A confirmation of the continuous chaotic motion of molecules is also Brownian motion - the continuous chaotic motion of microscopic particles that are insoluble in a liquid.
The movement of Brownian particles is explained by the chaotic movement of fluid particles that collide with microscopic particles and set them in motion. It has been experimentally proved that the speed of Brownian particles depends on the temperature of the liquid. The theory of Brownian motion was developed by A. Einstein. The laws of motion of particles are of a statistical, probabilistic nature. There is only one known way to reduce the intensity of Brownian motion - a decrease in temperature. The existence of Brownian motion convincingly confirms the motion of molecules.
Any substance consists of particles, therefore the amount of substance v is considered to be proportional to the number of particles, i.e. structural elements contained in the body.
The unit of quantity of a substance is the mole. A mole is the amount of a substance that contains as many structural elements of any substance as there are atoms in 12 g of C12 carbon. The ratio of the number of molecules of a substance to the amount of a substance is called the Avogadro constant:
The Avogadro constant shows how many atoms and molecules are contained in one mole of a substance. Molar mass - the mass of one mole of a substance, equal to the ratio of the mass of the substance to the amount of the substance:
Molar mass is expressed in kg/mol. Knowing the molar mass, you can calculate the mass of one molecule:
The average mass of molecules is usually determined by chemical methods, the Avogadro constant has been determined with high accuracy by several physical methods. The masses of molecules and atoms are determined with a considerable degree of accuracy using a mass spectrograph.
The masses of molecules are very small. For example, the mass of a water molecule:
The molar mass is related to the relative molecular mass Mg. Relative molecular weight is a value equal to the ratio of the mass of a molecule of a given substance to 1/12 of the mass of a C12 carbon atom. If the chemical formula of a substance is known, then its relative mass can be determined using the periodic table, which, when expressed in kilograms, shows the magnitude of the molar mass of this substance.
Molecular-kinetic theory is a branch of physics that studies the properties of various states of matter, based on the concept of the existence of molecules and atoms, as the smallest particles of matter. The ICT is based on three main principles:
1. All substances consist of the smallest particles: molecules, atoms or ions.
2. These particles are in continuous chaotic motion, the speed of which determines the temperature of the substance.
3. Between the particles there are forces of attraction and repulsion, the nature of which depends on the distance between them.
The main provisions of the MKT are confirmed by many experimental facts. The existence of molecules, atoms and ions has been proven experimentally, molecules have been sufficiently studied and even photographed using electron microscopes. The ability of gases to expand and occupy indefinitely the whole the volume provided by it is explained by the continuous chaotic movement of molecules. Elasticity gases, solid and liquid bodies, the ability of liquids
wetting some solids, the processes of coloring, gluing, keeping the shape of solids and much more indicate the existence of forces of attraction and repulsion between molecules. The phenomenon of diffusion - the ability of the molecules of one substance to penetrate into the gaps between the molecules of another - also confirms the basic provisions of the MKT. The phenomenon of diffusion explains, for example, the spread of odors, the mixing of dissimilar liquids, the process of dissolving solids in liquids, the welding of metals by melting them or by pressure. A confirmation of the continuous chaotic motion of molecules is also Brownian motion - the continuous chaotic motion of microscopic particles that are insoluble in a liquid.
The movement of Brownian particles is explained by the chaotic movement of fluid particles that collide with microscopic particles and set them in motion. It has been experimentally proved that the speed of Brownian particles depends on the temperature of the liquid. The theory of Brownian motion was developed by A. Einstein. The laws of motion of particles are of a statistical, probabilistic nature. There is only one known way to reduce the intensity of Brownian motion - a decrease in temperature. The existence of Brownian motion convincingly confirms the motion of molecules.
Every substance is made up of particles, so amount of substance considered to be proportional to the number of particles, i.e. structural elements contained in the body, v.
The unit of quantity of a substance is mol.mole- this is the amount of a substance containing as many structural elements of any substance as there are atoms in 12 g of carbon C 12. The ratio of the number of molecules of a substance to the amount of a substance is called constant Avogadro:
n a= N/ v. na = 6,02 10 23 mole -1 .
The Avogadro constant shows how many atoms and molecules are contained in one mole of a substance. molar mass called a quantity equal to the ratio of the mass of a substance to the amount of substance:
M = m/ v.
Molar mass is expressed in kg/mol. Knowing the molar mass, you can calculate the mass of one molecule:
m 0 = m/N = m/vN A= M/ N A
The average mass of molecules is usually determined by chemical methods, the Avogadro constant has been determined with high accuracy by several physical methods. The masses of molecules and atoms are determined with a considerable degree of accuracy using a mass spectrograph.
The masses of molecules are very small. For example, the mass of a water molecule: t = 29.9 10 -27 kg.
The molar mass is related to the relative molecular mass Mr. Relative molar mass is a value equal to the ratio of the mass of a molecule of a given substance to 1/12 of the mass of a C 12 carbon atom. If the chemical formula of a substance is known, then its relative mass can be determined using the periodic table, which, when expressed in kilograms, shows the magnitude of the molar mass of this substance.
Molecular Kinetic Theory (MKT)- This is a branch of physics that studies the properties of various states of matter, based on the concept of the existence of molecules and atoms as the smallest particles of matter. MKT is based on three main points:
1
. All substances are made up of tiny particles: molecules, atoms or ions.
2
. These particles are in continuous chaotic motion, the speed of which determines the temperature of the substance.
3
. Between the particles there are forces of attraction and repulsion, the nature of which depends on the distance between them, i.e. particles interact with each other.
The main provisions of the MKT are confirmed by many experimental facts.
The existence of molecules, atoms and ions has been proven experimentally, the molecules have been sufficiently studied and photographed using electron microscopes.
The ability of gases to expand indefinitely and occupy the entire volume provided to them is explained by the continuous chaotic movement of molecules.
The elasticity of gases, solids and liquids, the ability of liquids to wet some solids, the processes of coloring, gluing, maintaining the shape of solids, and much more indicate the existence of forces of attraction and repulsion between molecules.
Phenomenon diffusion- the ability of the molecules of one substance to penetrate into the gaps between the molecules of another - also confirms the basic provisions of the MKT. The phenomenon of diffusion explains, for example, the spread of odors, the mixing of dissimilar liquids, the process of dissolving solids in liquids, the welding of metals by melting them or by pressure. A confirmation of the continuous chaotic motion of molecules is also Brownian motion- continuous chaotic movement of microscopic particles insoluble in liquid. The movement of Brownian particles is explained by the chaotic movement of fluid particles that collide with microscopic particles and set them in motion. It has been experimentally proved that the speed of Brownian particles depends on the temperature of the liquid. The theory of Brownian motion was developed by A. Einstein.
Any substance consists of particles, so the amount of substance ν considered to be proportional to the number of particles contained in the body. The unit of quantity of a substance is the mole. The ratio of the number of molecules of a substance to the amount of a substance is called constant Avogadro: , N A \u003d 6.02 ∙ 10 23 mol -1.
The Avogadro constant shows how many atoms and molecules are contained in one mole of a substance.
Molar mass- the mass of one mole of a substance, equal to the ratio of the mass of the substance to the amount of the substance:. The molar mass is expressed in kg/mol. Knowing the molar mass, you can calculate the mass of one molecule: 
.
The masses of molecules are very small, for example, the mass of a water molecule: m=29.9∙10 -27 kg, so it is convenient to use not absolute values of the masses, but relative ones. The relative atomic masses of all chemical elements are indicated in the periodic table. By physical methods it was possible to determine the masses of some atoms in absolute units. This is how the atomic mass unit (a.m.u.) appeared, equal to 1/12 of the mass of carbon atoms: 1 amu =1, 66∙10 -2 7 .
Molar mass is related to relative molecular weight Mr. Relative molecular weight- this is a value equal to the ratio of the mass of a molecule of a given substance to 1/12 of the mass of a carbon atom. If the chemical formula of a substance is known, then its relative mass can be determined using the periodic table.