Materials that Expand on Freezing

Transition from liquid to solid

Water is well known for expanding as it freezes. There are other substances whose crystal structure is of an open, tetrahedral type that also exhibit this trick. They can be spotted because the solid floats as it melts. Post additional materials here or email to

Materials that expand on Freezing
Material  % expansion Freezing point Ref
silicon 10% 1414 ºC Integrated Materials, Inc
Gallium 3.1% 27.7 ºC
Germanium 947 ºC
Antimony  ?? 904 K
Bismuth 3.32% 544.7 K Also some of its alloys expand
Acetic Acid  ?? 290 K -
Water 8.1% 273.15 K For normal hexagonal ice - See Ice phase table below for special ice
Waters max density is at 4 ºC - thats why water freezes from the top

Phases of Ice
Phase Description
Amorphous ice

Amorphous ice is an ice lacking crystal structure. Amorphous ice exists in three forms: low-density (LDA) formed at atmospheric pressure, or below, high density (HDA) and very high density amorphous ice (VHDA), forming at higher pressures. LDA forms by extremely quick cooling of liquid water ("hyperquenched glassy water", HGW), by depositing water vapor on very cold substrates ("amorphous solid water", ASW) or by heating high density forms of ice at ambient pressure ("LDA").

Ice Ih Normal hexagonal crystalline ice. Virtually all ice in the biosphere is ice Ih, with the exception only of a small amount of ice in the form of Ic
Ice Ic Metastable cubic crystalline variant of ice. The oxygen atoms are arranged in a diamond structure. It is produced at temperatures between 130-150 K, and is stable for up to 200 K, when it transforms into ice Ih. It is occasionally present in the upper atmosphere.
Ice II A rhombohedral crystalline form with highly ordered structure. Formed from ice Ih by compressing it at temperature of 190-210 K. When heated it undergoes transformation to ice III.
Ice III A tetragonal crystalline ice, formed by cooling water down to 250 K at 300 MPa. Least dense of the high-pressure phases. Denser than water.
Ice IV Metastable rhombohedral phase. Does not easily form without a nucleating agent.
Ice V A monoclinic crystalline phase. Formed by cooling water to 253 K at 500 MPa. Most complicated structure of all the phases.
Ice VI A tetragonal crystalline phase. Formed by cooling water to 270 K at 1.1 GPa. Exhibits Debye relaxation.
Ice VII A cubic phase. The hydrogen atoms' position is disordered, the material shows Debye relaxation. The hydrogen bonds form two interpenetrating lattices.
Ice VIII A more ordered version of ice VII, where the hydrogen atoms assume fixed positions. Formed from ice VII by cooling it beyond 5 °C.
Ice IX A tetragonal metastable phase. Formed gradually from ice III by cooling it from −65 to −108 °C, stable below 140 K and pressures between 200 and 400 MPa. It has density of 1.16 g/cm³, slightly higher than ordinary ice.
Ice X Proton-ordered symmetric ice. Forms at about 70 GPa.
Ice XI An orthorhombic low-temperature equilibrium form of hexagonal ice. It is ferroelectric.
Ice XII A tetragonal metastable dense crystalline phase. It is observed in the phase space of ice V and ice VI. It can be prepared by heating high-density amorphous ice from 77 K to about 183 K at 810 MPa.

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