10TH GRADE · MOLECULAR KINETIC THEORY

Particles and amount of matter

Molecule mass, mole, number of particles and concentration.

22 minutes15 theory cards

LESSON MATERIAL

Basic Concepts

Mole

A quantity of a substance containing a number of particles equal to Avogadro's constant.

Mole is a convenient “portion” of microparticles. The number of particles is found as the product of the amount of substance and Avogadro's constant.

Ideal gas

A model of a gas whose particles are considered pointlike and interact only through elastic collisions.

This model describes well a fairly rarefied gas, when the intrinsic volume of the molecules and their attraction can be neglected.

LESSON MATERIAL

Physical quantities

Mass of one particle

m_0

The mass of an individual molecule or atom.

Unit: kilogram · $\mathrm{kg}$

Molar mass

M

The mass of one mole of a substance.

Unit: kilogram per mole · $\frac{\mathrm{kg}}{\mathrm{mol}}$

Relative molecular weight

M_r

The ratio of the mass of a molecule to the atomic mass unit.

Unit: dimensionless quantity

Avogadro's constant

N_A

The number of structural particles in one mole.

Unit: reverse mole · $\frac{1}{\mathrm{mol}}$

Number of particles

N

The number of particles in the system under consideration.

Unit: dimensionless quantity

Quantity of substance

\nu

The number of moles of a substance.

Unit: mole · $\mathrm{mol}$

Particle concentration

n

Number of particles per unit volume.

Unit: reciprocal cubic meter · $\frac{1}{\mathrm{m}^3}$

LESSON MATERIAL

Lesson formulas

Mass of one particle

m_0=\frac{M}{N_A}

The mass of one particle is equal to the molar mass divided by Avogadro's constant.

Molar and relative mass

M=M_r\,\frac{\mathrm{g}}{\mathrm{mol}}

The numerical value of the molar mass in grams per mole coincides with the relative molecular mass.

Number of particles

N=\frac{m}{M}N_A=\nu N_A

The number of particles is determined by the mass or amount of the substance.

Quantity of substance

\nu=\frac{m}{M}=\frac{N}{N_A}

The amount of a substance can be found by mass or number of particles.

Particle concentration

n=\frac{N}{V}

Concentration is equal to the number of particles per unit volume.

Avogadro's constant

N_A=6{,}02\cdot10^{23}\,\mathrm{mol}^{-1}

One mole contains approximately six point two ten to the twenty-third particles.

Related formulas

Quantity of substanceν · mole Molecular concentrationn · m⁻³ Molar massM · kg/mol

PRACTICE

Tasks on the topic

Molecular kinetic theory10 class · 12 problems