Plastic Ice (The Fourth Form of Water)
Plastic ice is a proposed hypothetical fourth phase of water that is distinct from liquid water, solid conventional ice (ice Ih), and steam. The existence of this proposed phase was suggested by researchers at the University of Bristol and published in a study in the journal Nature Communications in late 2024/early 2025.
Characteristics and Definition
- Hypothetical Phase: Plastic ice is not a form of water that has been observed in nature under standard conditions; rather, its properties were predicted using advanced computer simulations and quantum mechanics.
- A Solid with Fluidic Properties: The defining characteristic of this proposed phase is that while the oxygen atoms would form a rigid, fixed crystal lattice (a solid structure), the hydrogen atoms would be free to move around almost like a fluid within that lattice (a "plastic" property).
- Low Density: The simulations predict that plastic ice would be less dense than liquid water, unlike conventional ice, which floats. It would also possess low thermal conductivity, meaning heat would transfer through it slowly.
Scientific Significance and Context
The discovery is significant in the study of the complex phases of water, which already has over 20 known solid phases (different types of ice). The proposed plastic ice phase would represent a fundamentally new state of matter for water.
- Challenging Assumptions: The finding challenges the typical assumption in materials science that a material must be fully fluid (liquid) for its constituent parts to move dynamically.
- Implications for Research: While researchers have not yet created this state in a laboratory, the theoretical prediction has opened new avenues for understanding water's behavior under extreme, non-standard conditions. It highlights the potential for other materials to exist in similarly mixed solid/fluid states.
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