How are the smallest constituents of matter arranged?

🇫🇷 French Version

I— Case of water 💧

Pure water used in chemistry contains only water molecules.


Model of the H2O water molecule
Model of the water molecule

Water molecules are all identical.
They therefore have:


Molecules are incompressible.
Their volume does not change.
They are made of several hard spheres 🧱.

II— Molecular arrangements 🧩

Solid state
Enlargement or molecular model:

Molecular model of the solid state, ordered and closely packed molecules

Molecular speed: No movement
Molecular arrangement: Ordered molecules
Bond between nearby molecules: Stuck together

Liquid state
Enlargement or molecular model:

Molecular model of the liquid state, disordered and closely packed molecules

Molecular speed:
Low speed
Molecular arrangement:
Disordered molecules
Bond between nearby molecules: Weakly bonded

Vapour state
Enlargement or molecular model:

Molecular model of the gaseous state, molecules far apart and moving rapidly

Molecular speed: High speed (~ 1,000 km/h)
Molecular arrangement: Disordered molecules
Bond between nearby molecules: No bond

III— Molecular arrangements 🌫️

The solid state is compact and ordered.

In the solid state, molecules touch each other, do not move, and are ordered (case of crystals).


The liquid state is compact and disordered.

In the liquid state, molecules touch each other, move, and are disordered.


The gaseous state is dispersed and disordered.

In the vapour state, molecules do not touch each other, move rapidly, and are disordered.

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