The main criterion of nature is diversity. It amazes and makes you wonder: why are there so many substances around, different in their structure and properties? The answer lies in the field of elementary particles of which they consist. Molecules, atoms or ions are those bricks from which the compounds that form the basis of the manifested world are glued together. Our article will be devoted to the features of the properties of substances of a molecular and non-molecular structure, and the examples that we give will illustrate them.
The most expensive and hardest
Yes, it's all about him, about diamond. It doesn’t matter whether he adorns the crown of the Queen of England or serves as an element of a tool for cutting concrete, diamond has an atomic structure. The severity and grace of the tetrahedral crystal structure is amazing. Each carbon atom is surrounded by four other atoms lying in directions from the center of the geometric body to the vertices. Thus, four sigma bonds arise. They are the cause of exceptional hardness, low thermal conductivity, lack of electrical conductivity and significant diamond density.
Allotropic carbon modification
The non-molecular structure has a substance well known even to a schoolboy - graphite. Together with diamond and carbine, it is one of the allotropic forms of carbon. Pencil rods, fuel rods in nuclear reactors, electrodes in a plating bath consist of graphite. Oily to the touch, dark gray crystalline material with a faint metallic luster - it, like diamond, consists of carbon atoms. They are collected in layers that look like regular hexagons. The space of a graphite crystal is filled with freely moving electrons, creating an electron gas. Due to this, graphite, like metals, conducts electric current and heat. The distance between the layers of the substance is approximately 0.335 nm, so they easily come off from each other, leaving a scaly gray trace on the surface when pressed. The description of substances of non-molecular structure, examples of which we have cited, confirm the fact that the properties of chemical compounds are determined by the shape of their crystal lattices and depend on how their atoms, molecules or ions are interconnected.
Greenhouse effect: who is to blame?
Global warming, with sullen obstinacy approaching our planet, is caused for many reasons. The main one, according to ecologists, is associated with a sharp increase in the concentration of substances with a molecular structure, such as carbon dioxide and carbon monoxide, in the air shell of the Earth. Nonpolar carbon dioxide molecules have a linear structure. At the nodes of the crystal lattice are electrically neutral particles - molecules. The molecular crystalline structure leads to a low boiling point and high volatility of the compound.
The substance is included in important natural organic cycles, for example, serves as an acceptor in the reactions of the Calvin cycle that occur during photosynthesis. At high temperatures, the compound exhibits oxidizing properties and is used in the non-ferrous metal industry to reduce metals from their oxides. Man uses carbon dioxide in many areas: in sugar production, in fire extinguishers, and in the form of dry ice - for storing quickly spoiled food. Further we will give more examples of substances of molecular structure that play key roles in our nature.
Source of Life
Is there any other chemical compound comparable in importance to water? This is the cradle in which the first living objects arose, as well as the main component of the biosphere, an indispensable chemical component of almost any biological object. Its polar molecules can dissolve a huge number of different substances, and anomalous properties, such as specific heat, allow water to accumulate and hold huge reserves of thermal energy.
This contributes to the regulation of average temperatures on the land surface and prevents the danger of its sudden overcooling in severe winters or overheating in summer. In the body of animals and humans, water, which is part of the cytoplasm of cells, tissue and intercellular fluid, promotes an even distribution of thermal energy between tissue systems, primarily due to blood vessels. All the most important biochemical processes that make up the basis of metabolism occur in aqueous solutions. The entry of compounds into the cell and the removal of decay products also occurs only in the dissolved state. Let us consider further examples of substances of molecular structure.
Sucrose
Consider an example of an organic compound related to oligosaccharides. This is sucrose, otherwise called cane, or beet sugar. The most important and beloved by all food product with good digestibility and high calorie content. In the process of hydrolysis, due to pancreatic juice enzymes, primarily amylase, sucrose is broken down into glucose and fructose molecules. It has been established that molecules of substances of molecular and non-molecular structures behave differently with respect to polarized light.
Sucrose is an optically active compound due to the presence of asymmetric carbon atoms in its molecules. The substance has a low melting point of -186 º, while turning into a viscous mass of brown color - caramel. The molecular crystal lattice also determines other properties of sucrose: low boiling point, inability to conduct current and poor thermal conductivity.
The molecular theory of the structure of substances
Chemistry as a science has its foundation in the form of major laws and postulates. The atomic-molecular theory created by MV Lomonosov, as well as the study of phenomena such as Brownian motion and diffusion, led to the appearance of a whole series of studies. They concerned the study of the structure of chemical compounds. The experiments of L. Boltzmann and D. Maxwell accelerated the appearance of the molecular theory of the structure of matter. It echoes Cartesian ideas about the corpuscular structure of the world and the provisions of the theory of M. Lomonosov. So, it says that material objects have an atomic, molecular or ionic composition, are constantly moving, and at this moment they can interact with each other through elastic collisions. In modern science, theory is mainly applied in nature and has been used in the development of disciplines such as static mechanics and physical kinetics.
Ionic type compounds
We conclude the study of substances of a molecular and non-molecular structure by examining compounds whose crystal lattice consists of ions.
These include all salts. Physical properties: hardness and strength, simultaneously accompanying fragility, as well as the ability of their solutions to conduct electric current, are due to the structure of the crystal lattice. So, in the nodes of the crystal of sodium chloride are opposite ions of sodium and chlorine. Both the solution and the melt of the substance conducts electric current well and refers to electrolytes. That is why, due to the directed movement of cations and anions, salts are second-type conductors, which is confirmed by the basic principles of the theory of electrical dissociation.
In our article, we examined the structure and properties of substances of molecular and non-molecular structure, and also gave examples illustrating them.