liquid

Introduction
Physical properties of liquids
Transitions between states of matter
Behaviour of pure liquids
- Phase diagram of a pure substance
- Representative values of phase-diagram parameters
- Behaviour of substances near critical and triple points
- Surface tension
- Molecular structure of liquids
- Speed of sound and electric properties
Solutions and solubilities
- Classes of solutions
  - Electrolytes and nonelectrolytes
  - Weak electrolytes
  - Endothermic and exothermic solutions
- Properties of solutions
  - Composition ratios
    - Molarity
    - Molality
    - Formality
    - Mole fraction and mole percentage
    - Volume fraction
  - Equilibrium properties
    - Fugacity
    - Raoult’s law
    - Partial miscibility
  - Colligative properties
    - Rise in boiling point
    - Decrease in freezing point
    - Osmotic pressure
  - Transport properties in solutions
    - Viscosity
    - Thermal conductivity
    - Diffusivity
- Thermodynamics and intermolecular forces in solutions
  - Energy considerations
  - Effects of molecular structure
  - Molecular structure and charge distribution
    - Polar molecules
    - Nonpolar molecules
  - Effects of chemical interactions
    - Hydrogen bonding: association
    - Hydrogen bonding: solvation
- Theories of solutions
  - Activity coefficients and excess functions
  - Regular and athermal solutions
    - Regular solutions
    - Athermal solutions
  - Associated and solvated solutions
  - Solutions of electrolytes
- Solubilities of solids and gases

References & Edit History Quick Facts & Related Topics

Images & Videos

The science of surface tension explained

How different solutions conduct electricity

Diagram showing the phase changes of matter with three circles labeled solid, liquid, and gas. Arrows indicate transitions: melting and freezing between solid and liquid, evaporation and condensation between liquid and gas, and sublimation and deposition between solid and gas.

Diagram showing four physical states of matter: solid with tightly packed molecules, liquid with loosely packed molecules, gas with widely spaced molecules, and plasma with free electrons and nuclei, each labeled with descriptions and an arrow indicating increasing energy.

An illustration shows an ice cube labeled solid, a puddle labeled liquid, and rising steam labeled gas, representing the three states of matter: ice, water, and water vapor, with the sun in the background.

At a Glance

liquid summary

liquid

state of matter

Also known as: liquid state

Written by

John M. PrausnitzAll

Fact-checked by

Britannica Editors

Last updated

Oct. 10, 2026 •History

liquid, in physics, one of the three principal states of matter, intermediate between gas and crystalline solid. The most obvious physical properties of a liquid are its retention of volume and its conformation to the shape of its container. When a liquid substance is poured into a vessel, it takes the shape of the vessel, and, as long as the substance stays in the liquid state, it will remain inside the vessel. Furthermore, when a...

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