What is a density unit? Find out the features of this physical quantity.
This term is an important indicator of oil, as well as various oil products.
Features of the term
In modern petrochemistry, such substance density units are used as kg / m3, as well as g / m3. Using a similar value, calculations are carried out related to the determination of the mass of a substance. In the presence of volume, as well as with a known density of the substance, it is possible to determine the amount of oil products.
Value determination
The saturation of a mixture of a substance or pure component is the amount of mass that is contained in one unit volume. The unit of density in SI is kg / m3. The value is taken as the mass of one cubic meter of distilled water, which is taken at a temperature of four degrees.
Basically, it is not its absolute value that is calculated for a substance or mixture of components, but the relative density, which expresses the ratio of the mass of the mixture (component) to pure water of equal volume.
According to the numerical indicator, the values of relative and absolute density are the same, there are differences only in dimension. Relative has no unit of density.
In our country, there is a special GOST 3900, according to which the density is determined at a temperature of +20 degrees Celsius.
For export oil and petroleum products use special international standards for calculating the density. They involve the use of hydrometers and digital density analyzers.
In the United States of America and England, arbitrary values, such as degrees, are used, even special degrees of Baumet and API are introduced. Between them there is a relationship expressed by arithmetic equations.
Some references cite the density designation d204. In reality, this physical quantity is determined at various temperatures, using the value of the coefficient of volume expansion.
Density as an independent indicator is important precisely for the petrochemical industry. In addition, this physical term is used to determine the structural group composition by analyzing a mixture of hydrocarbon fractions.
What determines the density
Density units indicate that this physical quantity is related to volume and mass. What other indicators can affect the density value?
The density is influenced by the chemical nature of the constituent substances, the fractional composition, the molecular weight of the constituent substances, the presence of dissolved substances, and the content of resinous substances. Depending on the depth and geological age, a change in the density of oil occurs. In chemistry, such units of density of a substance as g / cm3 are used.
Density Determination Methods
In Russia, the areometric and pycnometric methods are used to determine the density. The second option is a long and laborious method, it gives high measurement accuracy. Its basis is a comparison of the mass of the calculated volume of the analyzed oil or oil product with the mass of water at equal temperatures. The result is a unit of density accurate to 0.0001. Pycnometers are glass vessels with a ground stopper. The volume of blood vessels allowed in 1, 5, 25 ml.
What is the specificity of the areometric method? There is an international standard according to which the density of liquid petroleum products and pure oil can be determined by laboratory methods. The method involves the use of a glass hydrometer at +15 and +20 degrees Celsius.
The hydrometer is a cylindrical vessel, at the bottom there is ballast. Its location must be symmetrical. Many hydrometers have a thermometer. A special scale is made on the device, a unit of density is indicated. In order to increase the accuracy of definitions, you can use a set of hydrometers, using several additional divisions on the scale.
Using this method, the density of mobile transparent solutions is determined using the coincidence of the lower meniscus with the base of the hydrometer. When detecting the density of opaque liquids, the hydrometer scale is read, choosing the match with the rod of the upper meniscus.
With a smooth immersion of the hydrometer, after its establishment, the density parameters are calculated. In the event that there are differences from a temperature of +20 degrees, density is determined at the existing temperature indicator, then recalculation is carried out.
Density Calculations
In everyday life, people often use comparative expressions: “light as air”, “heavy as lead”. Moreover, almost none of them thinks about whether they have a certain meaning.
In the school physics course, children are offered calculations in which three physical quantities are connected: density, mass, volume. For example, it is proposed to calculate the mass of copper and steel bars having the same volume. To cope with such a task, an indicator such as density is needed. The denser the metal, the greater mass the bar will have.
How to measure the mass of lead parts that have different weights? First you need to determine the height, width, length of each of them, calculate the volume by the obtained indicators. Then you can use the lever scales, a set of goods. To determine the density, it is necessary to find the ratio of mass to volume of the object.
Conclusion
What is density? This is a physical quantity that characterizes a particular substance. It is defined as the ratio of the mass of a given substance to volume. This parameter is indicated by the letter (ro), the basic unit of measure in the international SI system is kg / m3. It characterizes the substance itself, does not depend on what is the volume or mass of the original sample. With a three-fold increase in the mass of the mixture or pure substance, the volume will decrease exactly the same amount, while the density value remains constant.