Each object surrounding a person is made of certain raw materials. Various materials act in its quality. In order to use them more efficiently, first of all, one should carefully study their inherent properties and characteristics.
Property Types
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 physicochemical.
Physical properties
The physical properties of materials give a characteristic of their structure, as well as their relation to any kind of processes (physical nature) that come from the external environment. These properties may be:
- Specific characteristics of the structure and structural characteristics - true, average and bulk density; closed, open or total density.
- Hydrophysical (response to exposure 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.
All of them relate to the basic physical properties of materials and substances.
Specific characteristics
True density is the 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 remain in absolute density, that is, without voids and pores. The average density is the 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.
Bulk materials 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 the material is a value that expresses the degree of filling the total volume of the substance with pores.
Hydrophysical properties
The consequences of exposure to water or frosts in a material 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. A high level of porosity plays an important role.
Moisture recovery 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, they dry up until their moisture content is equal to the environment.
Hygroscopicity is a property involving the absorption of water vapor by an object from the outside. For example, wood is capable of absorbing a lot of moisture, as a result of which its mass grows, the level of strength decreases and size changes.
Shrinkage or shrinkage is a hydrophysical property of materials, which provides for a decrease in its volume and size during the drying process.
Water resistance is the ability of a substance to maintain its strength as a result of moisture.
Frost resistance is the ability of a material saturated with water to withstand repeatedly freezing and thawing without reducing the level of strength and destruction.
Thermophysical Properties
As mentioned above, such properties describe the effects of 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 during heating and the release of the same amount of heat during cooling.
Fire resistance is the physical property of a material that describes its ability to withstand the effects of high temperature and liquid in a fire. In accordance with the level of fire resistance, materials and substances can be non-combustible, hardly combustible 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, the 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 properties that describe the ability of materials to respond to environmental influences leading to changes in their chemical structure. In addition, characterizing substances belong to such properties from the side of their influence on the structures of other objects. From the point of view of chemical properties, materials are described by their solubility, acid and alkali resistance, gas resistance and anticorrosion.
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 the material to the effects of mineral and organic acids.
Alkali resistance is taken into account during technological processing of substances, as it helps to recognize their nature.
Gas resistance characterizes the ability of an object to withstand interaction with gases that make up the atmosphere.
Using the indicator of anticorrosion, you can find out how much the substance is susceptible to destruction by corrosion resulting from exposure to the external environment.
Mechanical properties
Mechanical properties are called reactions of materials to mechanical loads applied to them.
Physical and mechanical properties of materials often intersect, however, there are a number of exclusively mechanical indicators. On the part of the mechanics of the substance are characterized by elasticity, strength, hardness, ductility, fatigue, brittleness, etc.
Resilience is the ability of bodies (solid) to resist influences aimed at changing their volume or shape. An object with a high value of elasticity is resistant to mechanical stresses and is able to independently recover, returning to its original state after the termination of exposure.
Strength shows how resistant the material is to destruction. Its maximum value for a particular object is called 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 the cumulative process in which the level of internal stress of a material increases as a result of repeated mechanical influences. This level will increase until it crosses the elastic limit, as a result of which the material begins to collapse.
One of the most common properties is hardness. It represents the level of resistance of an object to indentation.
Method for 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 specific indicator.
In order to determine the density of the sample material, often use the method of hydrostatic weighing. It provides for measuring the volume of a substance by the mass of liquid displaced by it. The true density is calculated mathematically by dividing the mass of the object by its absolute volume.
An experiment to determine the amount of water absorption is carried out in several stages. First of all, the 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 taken out of 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 the basic chemical properties of substances are determined by creating conditions for the interaction of the object of study with various reagents. Water, oil, gasoline and other solvents are used to determine solubility. The level of oxidation and susceptibility to corrosion is determined using various oxidizing agents that contribute to general, petting and intergranular reactions.
Determination of mechanical characteristics
The mechanical properties of substances to a large extent depend on their structure, the forces that are applied to them, temperature and external pressure. Almost all mechanical characteristics of materials are established during laboratory tests. The simplest of these are tension, compression, torsion, loading and bending. So, for example, the tensile strength of a material during bending and compression is determined using a hydraulic press.
In addition, when determining the mechanical properties, special formulas are also used, which are often based on the mass of the object and its volume.