Liquid
A state of matter with definite volume but no fixed shape.
Liquid is a state of matter with a definite volume but no fixed shape. It is a form of condensed matter alongside solids and a form of fluid alongside gases. Liquids are composed of atoms or molecules held together by intermolecular bonds of intermediate strength, allowing particles to move around one another while remaining closely packed.
- state
- Liquid
- key_property
- Definite volume, no fixed shape
- common_examples
- Water, ethanol, mercury, bromine
- compressibility
- Nearly incompressible
- surface_tension_range
- Tens to hundreds of mJ/m2
- universe_abundance
- Least common state of matter in the known universe
Lore & Background
Liquids adapt to the internal shape of their container when subject to a force such as gravity. They are nearly incompressible, maintaining volume even under pressure. The density of a liquid is usually close to that of a solid and much higher than that of a gas. As temperature increases, molecules vibrate more intensely, increasing distances between them; at the boiling point, cohesive forces fail and the liquid becomes a gas. As temperature decreases, molecules draw closer; at the freezing point, crystallization typically occurs and the liquid becomes a solid.
Reader's Guide
Liquid water is vital in chemistry and biology and necessary for all known forms of life. Although abundant on Earth, liquid is the least common state of matter in the known universe, requiring a narrow temperature and pressure range. Liquids transmit hydraulic power due to incompressibility, but this property also causes phenomena such as water hammer and cavitation. Surface tension, arising from unbalanced molecular forces at surfaces, causes liquids to minimize surface area, forming spherical drops and bubbles. Surface tension also governs wettability: common liquids have tensions in the tens of mJ/m2, while liquid metals like mercury have tensions in the hundreds of mJ/m2. Many gases can be liquefied by cooling, though not all at atmospheric pressure; carbon dioxide, for example, requires pressures above 5.1 atm to become liquid. Liquid helium is exceptional in that it does not solidify even at absolute zero under standard pressure due to quantum properties.
Did You Know?
- Only two elements are liquid at standard conditions for temperature and pressure: mercury and bromine.
- Water between 0 °C and 4 °C is a notable exception to the rule that liquids expand when heated and contract when cooled.
- Liquid helium does not become solid even at absolute zero (0 K) under standard pressure due to its quantum properties.
- Carbon dioxide solidifies directly into dry ice at atmospheric pressure and can only be liquefied at pressures above 5.1 atm.
More in Thermodynamics And Statistical Mechanics 1-22
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