Molecular physics is an extensive branch of physics that studies the structure of matter at the molecular level, changes in the macroparameters of a system under the influence of the external environment, and phase transitions. The properties of polymers and plasma are also explored by molecular physics. The formulas and definitions of this section, which are useful in solving problems, are given in this article.
Section Concepts
A molecule is the smallest unit of a substance that has all its properties.
An ideal gas is a gas for which the intermolecular interaction strength is zero, the molecules are considered as material points, and the impacts between them are absolutely elastic. Many molecular physics formulas are applied specifically to the ideal gas.
Energy is a quantity that characterizes the ability of a system to do work.
Work - the amount of energy transferred to the system through a change in its parameters.
Other concepts in this section: temperature, internal energy, potential energy, diffusion, thermal conductivity, amount of substance, heat capacity, evaporation, condensation, crystallization, saturated steam.
Basic formulas
Molecular physics formulas establish the relationship between various system parameters. The main formulas in this section include the Clapeyron equation, which describes the state of an ideal gas, the laws of Boyle, Charles and Gay-Lussac.
The Clapeyron equation is written as follows:
pV = nRT
Here p is pressure, n is the amount of substance in moles, R is the universal gas constant, T is the temperature in kelvins, V is the volume occupied by the gas.
From this formula of molecular physics with the help of simple transformations, other laws of state are also obtained:
pV = const (the formulation of the Boyle-Mariotte law, which is applied to the isothermal process);
V / T = const (the first Gay-Lussac law that applies to the isobaric process);
p / T = const (Charles law, applies to the isochoric process).
Other important formulas of molecular physics:
n = m / M = N / Na (formula for finding the amount of substance).
p = nkT.
In the last formula, n is the concentration, k is the constant, Boltzmann constant.
E = (3NkT) / 2 (formula for finding thermal energy).
p = p 1 + p 2 + ... + p i (the formula for determining the pressure of a mixture of gases, known as the Dalton law).
Formulas of thermodynamics and statistical physics
Statistical physics is also a branch of molecular physics. Some formulas of molecular physics used in statistical physics and thermodynamics are given above.
Q = mc (t 2 -t 1 )
Q = A + (U2-U 1 ) (U i - internal energy)
dH = TdS + Vdp
Here H is the enthalpy.
G - Gibbs energy, or thermodynamic potential.
V = dG / dp
S = -dG / dT (S - entropy, value introduced by Clausius, measure of probability).