Let's talk about the fact that such an amount of a substance as this term is used in subjects of the natural science cycle. Since quantitative relations in chemistry and physics are given serious attention, it is important to know the physical meaning of all quantities, their units of measurement, and their field of application.
Designation, definition, units
In chemistry, quantitative relationships are of particular importance. For calculations using equations, special quantities are used. In order to understand what such an amount of substance is in chemistry, let us define the term. This is a physical quantity that characterizes the number of similar structural units (atoms, ions, molecules, electrons) present in a substance. To understand what such a quantity of substance is, we note that this quantity has its own designation. When carrying out calculations involving the use of this value, use the letter n. The units of measurement are mol, kmol, mmol.
Value
Eighth graders, who still do not know how to write chemical equations, do not know what is the amount of substance, how to use this value in the calculations. After becoming acquainted with the law of constancy of the mass of substances, the meaning of this quantity becomes clear. For example, in the reaction of burning hydrogen in oxygen, the ratio of reacting substances is two to one. If the mass of hydrogen entering the process is known, the amount of oxygen participating in the chemical reaction can be determined.
The use of formulas for the amount of substance can reduce the ratio between the starting reagents, simplify the calculation. What is the amount of substance in chemistry? From the point of view of mathematical calculations, these are stereochemical coefficients set in the equation. They are used in order to carry out certain calculations. So how to count the number of molecules is inconvenient, it is they who use the Mole. Using the Avogadro number, it can be calculated that 1 mol of any reagent includes 6 · 1023 mol −1 .
Calculations
Want to understand what is the amount of substance? In physics, this value is also used. It is needed in molecular physics, where pressure, volume of gaseous substances are calculated according to the Mendeleev-Clapeyron equation. To perform any quantitative calculations, the concept of molar mass is used.
By it is meant that mass which corresponds to one mole of a specific chemical substance. The molar mass can be determined through the relative atomic masses (their sum, taking into account the number of atoms in the molecule) or determined through the known mass of the substance, its quantity (mol).
Not a single task of a school chemistry course related to calculations by an equation can do without the use of a term such as “quantity of substance”. Possessing the algorithm, one can cope not only with ordinary software calculations, but also with complex olympiad tasks. In addition to calculations through the mass of a substance, it is also possible using this concept to carry out calculations through a molar volume. This is relevant in cases where gaseous substances participate in the interaction.