States of Matter, Classification, and Chemical Properties

Classified in Chemistry

Written on December 8, 2025 in English with a size of 4.49 KB

Classification of Substances

Substances can be classified according to different criteria:

Natural and Artificial Substances
Natural substances are those that exist in nature. Artificial substances are those formed from natural substances by chemical processes (man-made).
Homogeneous and Heterogeneous Mixtures
If we observe a substance that consists of several components and perceive distinct parts, we call it heterogeneous. Conversely, if we do not perceive a mixture, it is a homogeneous substance.
Pure Substances and Mixtures
Matter that contains a single substance is called a pure substance. Conversely, if it is formed by more than one substance, we call it a mixture.
Solid, Liquid, and Gas States
This is the best-known classification, made according to the state of matter. We will focus on this classification and its properties.

Properties of Solids, Liquids, and Gases

Solids, liquids, and gases possess distinct physical properties:

Properties of Solids

They have their own shape, often regular.
They are practically incompressible, so their volume is constant.
Their density is quite close to that of liquids.
They do not flow.

Properties of Liquids

They take the shape of their container.
They are compressed with difficulty, so their volume is constant.
They are denser than gases.
They can flow.

Properties of Gases

They do not have their own shape (they fill the container).
They are easily compressed and expanded, filling the entire volume of their container.
Their densities are very low compared with those of liquids and solids.
They can flow.
They exert forces on all walls of their container.

Phase Changes of Matter

We call state changes (or phase transitions) the transformations occurring in substances. There are several types, some occurring when temperature increases and others when temperature decreases:

When the Temperature Rises (Endothermic Changes)

From solid to liquid: Melting.
From liquid to gas: Evaporation (or Vaporization).
From solid to gas: Sublimation.

When the Temperature Decreases (Exothermic Changes)

From gas to liquid: Condensation.
From liquid to solid: Solidification.
From gas to solid: Sublimation (or Deposition).

Osmotic Pressure Calculation

$\ Pi = R \ cdot T \ cdot c$

Where:

Π: Is the osmotic pressure in atmospheres (atm).
R: Is the universal ideal gas constant (although despite its name, it not only applies to gases, as is the case here). Its value is 0.082 atm · L · mol^-1 K^-1.
T: Is the absolute temperature, in kelvin (K).
c: Is the molar concentration or molarity of the solution, measured in mol/L^-1.

Calculation of Boiling Point

The normal boiling point can be calculated using the Clausius-Clapeyron formula:

$T_B = \ Bigg (\ frac {\, R \, \ ln (P_0)} {\ Delta H_ {vap}} + \ frac {1} {t_0} \ Bigg) ^ {-1}$

Where:
T_B	= Normal boiling point in Kelvin (K)
R	= Ideal gas constant, 8.314 J · K^-1 mol^-1
P₀	= Vapor pressure at a given temperature in atmospheres (atm)
ΔH_vap	= Heat of vaporization of the liquid, J/mol
T₀	= The given temperature in Kelvin (K)
ln	= Natural logarithm (logarithm to base e)

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