Every object that surrounds a person is made from a certain raw material. It serves as a variety of materials. In order to use them more effectively, first of all, you should carefully examine their inherent properties and characteristics.
Types of properties
Currently, researchers have identified three main types of material properties:
- physical;
- chemical;
- mechanical.
Each of them describes certain characteristics of a particular material. In turn, they can be combined, for example, the physical and chemical properties of materials are combined into physical and chemical properties.
Physical properties
The physical properties of materials characterize their structure, as well as their relationship to any kind of processes (of a physical nature) that come from the external environment. These properties can be:
- Specific characteristics of the structure and structural characteristics - true,average and bulk density; closed, open or total density.
- Hydrophysical (response to water or frost) - water absorption, moisture loss, humidity, frost resistance.
- Thermophysical (properties arising under the influence of heat or cold) - thermal conductivity, heat capacity, fire resistance, fire resistance, etc.
They all refer to the basic physical properties of materials and substances.
Specific characteristics
True density is a physical property of materials, which is expressed by the ratio of the mass of a substance to its volume. In this case, the object under study must be in absolute density, that is, without voids and pores. The average density is called a physical quantity, which is determined by the ratio of the mass of a substance to the volume occupied by it in space. When calculating this property, the volume of an object includes all internal and external pores and voids.
Loose substances are characterized by such a physical property of materials as bulk density. The volume of such an object of study includes not only the porosity of the material, but also the voids formed between the elements of the substance.
The porosity of a material is a value that expresses the degree of filling of the total volume of a substance with pores.
Hydrophysical properties
The consequences of exposure to water or frost largely depend on the degree of its density and porosity, which affect the level of water absorption,water permeability, frost resistance, thermal conductivity, etc.
Water absorption is the ability of a substance to absorb and retain moisture. The high level of porosity plays an important role in this.
Moisture return is a property opposite to water absorption, that is, it characterizes the material from the side of moisture return to its environment. This value plays an important role in the processing of certain substances, for example, building materials, which have high humidity during the construction process. Thanks to moisture release, they dry up until their humidity is equal to the environment.
Hygroscopicity is a property that provides for the absorption of water vapor by an object from the outside. For example, wood can absorb a lot of moisture, causing it to increase in weight, decrease strength, and change size.
Shrinkage or shrinkage is a hydrophysical property of materials, which involves a decrease in its volume and size in the process of drying.
Water resistance is the ability of a substance to retain its strength as a result of moisture.
Frost resistance is the ability of a material saturated with water to withstand repeated freezing and thawing without reducing the level of strength and destruction.
Thermophysical properties
As mentioned above, such properties describe the effects of exposure to heat or cold on substances and materials.
Thermal conductivity is the ability of an object to transfer heat from surface to surface through its thickness.
Heat capacity is a property of a substance that provides for the absorption of a certain amount of heat when heated and the release of the same amount of heat when cooled.
Fire resistance is a physical property of a material that describes its ability to withstand high temperatures and liquids in a fire. According to the level of fire resistance, materials and substances can be fireproof, slow-burning and combustible.
Refractoriness is the ability of an object to withstand prolonged exposure to high temperatures without subsequent melting and deformation. Depending on the level of refractoriness, substances can be refractory, refractory and fusible.
Vapor and gas permeability is the physical property of materials to pass air gases or water vapor through themselves under pressure.
Chemical properties
Chemical properties are called properties that describe the ability of materials to respond to environmental influences leading to changes in their chemical structure. In addition, these properties also include characterizing substances in terms of their influence on the structures of other objects. From the point of view of chemical properties, materials are described by the level of solubility, acid and alkali resistance, gas resistance and anti-corrosion.
Solubility refers to the ability of a substance to dissolve in water, gasoline, oil, turpentine and other solvents.
Acid resistance indicates the level of resistance of a material tomineral and organic acids.
Alkali resistance is taken into account in the technological processing of substances, as it helps to recognize their nature.
Gas resistance characterizes the ability of an object to resist interaction with gases that are part of the atmosphere.
Using the anti-corrosion index, you can find out how much a substance can be destroyed by corrosion resulting from exposure to the external environment.
Mechanical properties
Mechanical properties are the reactions of materials to mechanical loads applied to them.
Physical and mechanical properties of materials often overlap, but there are a number of purely mechanical properties. From the side of mechanics, substances are characterized by elasticity, strength, hardness, plasticity, fatigue, brittleness, etc.
Elasticity is the ability of bodies (solid) to resist influences aimed at changing their volume or shape. An object with a high elasticity value is resistant to mechanical stress and is able to self-repair, returning to its original state after the cessation of exposure.
Strength indicates how resistant a material is to breaking. Its maximum value for a particular object is called the tensile strength. Plasticity also refers to strength indicators. It is a property (characteristic of solids) to irrevocably change its appearance (deform) under the influence of forces emanating from outside.
Fatigue is a cumulative process in which, as a result of repeated mechanical impacts, the level of internal stress of the material increases. This level will increase until it crosses the elastic limit, causing the material to begin to break down.
One of the most common properties is hardness. It represents the level of resistance of an object to indentation.
Method of determining physical properties
In order to find out certain physical properties of a material, various methods are used, each of which is aimed at studying a certain indicator.
To determine the density of a material sample, the hydrostatic weighing method is often used. It involves measuring the volume of a substance by the mass of the liquid it displaces. True density is calculated mathematically by dividing an object's mass by its absolute volume.
The experiment to determine the amount of water absorption is carried out in several stages. First of all, a material sample is weighed, its dimensions are measured and the volume is calculated. After that, it is immersed in water for 48 hours to saturate with liquid. After 2 days, the sample is removed from the water and immediately weighed, after which the water absorption of the material is calculated mathematically.
Most methods for determining the physical properties of materials in practice come down to the use of special formulas.
Determination of chemical properties
All basic chemical properties of substances are determined by creating conditions for the interaction of the object of study with various reagents. To determine the solubility, water, oil, gasoline and other solvents are used. The level of oxidation and susceptibility to corrosion is determined using various oxidizing agents that promote general, petting and intergranular reactions.
Determination of mechanical characteristics
The mechanical properties of substances largely depend on their structure, the forces that are applied to them, temperature and external pressure. Almost all mechanical characteristics of materials are established in the course of laboratory tests. The simplest of these are tension, compression, torsion, loading and bending. So, for example, the tensile strength of the material in bending and compression is determined using a hydraulic press.
In addition, when determining mechanical properties, special formulas are also used, which are often based on the mass of an object and its volume.
