What is the unit of density? Let us find out the features of this physical quantity.
This term is an important indicator of oil, as well as various petroleum products.
Features of the term
Modern petrochemistry uses such units of substance density as kg/m3 and g/m3. With the help of 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.
Determining the value
The saturation of a mixture of a substance or a pure component is the amount of mass that is contained in one unit of 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.
In numerical terms, the values of relative and absolute density are the same, there are only differencesby dimension. Relative has no density unit.
In our country there is a special GOST 3900, according to which density is determined at a temperature of +20 degrees Celsius.
For export oil and oil products, special international standards for density calculation are used. They involve the use of hydrometers and digital density analyzers.
In the United States of America and England, conventional values are used, such as degrees, even special degrees of Baumé and API have been introduced. There is a relationship between them, expressed by arithmetic equations.
Some reference materials mention the density designation d204. In reality, this physical quantity is determined at various temperatures using the value of the coefficient of volumetric expansion.
Density as an independent indicator is important for petrochemistry. In addition, this physical term is used in determining 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?
Density is affected by the chemical nature of constituent substances, fractional composition, molecular weight of constituent substances, the presence of dissolved substances, the content of resinous substances. ATDepending on the depth of occurrence and geological age, the oil density changes. In chemistry, such units of measurement of the density of a substance as g/cm3 are used.
Methods for determining density
In Russia, the hydrometric 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 with an accuracy of 0.0001. Pycnometers are glass vessels with a ground stopper. The volume of vessels is allowed in 1, 5, 25 ml.
What is the specificity of the hydrometric method? There is an international standard by which it is possible to determine the density of liquid petroleum products, pure oil, in a laboratory way. The method involves the use of a glass hydrometer at +15 and +20 degrees Celsius.
The hydrometer is a cylindrical vessel with ballast at the bottom. Its location must be necessarily symmetrical. Many hydrometers have a thermometer. A special scale is made on the device, the unit of density is indicated. In order to increase the accuracy of the determinations, you can use a set of hydrometers using a few additional divisions on the scale.
This method determines the density of mobile transparent solutions, using the coincidence of the lower meniscus with the base of the hydrometer. When detecting densityopaque liquids, read the hydrometer scale, choosing a match with the upper meniscus rod.
When the hydrometer is smoothly immersed, after its establishment, the density parameters are calculated. In the event that there are differences from the temperature of +20 degrees, the density is determined at the existing temperature indicator, then the recalculation is carried out.
Density calculations
In everyday life, people often use comparative expressions: "light as air", "heavy as lead". At the same time, almost none of them think about whether they have a certain meaning.
In the school physics course, children are offered calculations in which three physical quantities are related: density, mass, volume. For example, it is proposed to calculate the mass of copper and steel bars that have the same volume. To cope with such a task, you need such an indicator as density. The denser the metal, the more mass the bar will have.
How to measure the masses of lead parts that have different weights? First you need to determine the height, width, length of each of them, calculate the volume from the obtained indicators. Then you can use lever scales, a set of goods. To determine the density, you need to find the ratio of the mass to the volume of the object.
Conclusion
What is density? This is a physical quantity that characterizes a certain substance. It is defined as the ratio of the mass of a given substance to its volume. This parameter is denoted by the letter (ro), the main unit of measurement in the internationalSI system is kg/m3. It characterizes the substance itself, does not depend on the volume or mass of the original sample. When the mass of a mixture or a pure substance is increased by a factor of three, the volume will decrease by exactly the same amount, while the density value remains constant.
