TERMIUM Plus^®

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When the temperature sinks on a cold winter's day water vapour becomes water and water becomes ice. These so-called phase transitions and the changed states of matter can be roughly described and understood with classical physics. What happens when the temperature falls is that the random heat movement in gases, liquids and solid bodies ceases. But the situation becomes entirely different when the temperature sinks further and approaches absolute zero, -273.15°C. In samples of liquid helium what is termed superfluidity occurs, a phenomenon that cannot be understood in terms of classical physics. When a liquid becomes superfluid its atoms suddenly lose all their randomness and move in a coordinated manner in each movement. This causes the liquid to lack all inner friction: It can overflow a cup, flow out through very small holes, and exhibits a whole series of other non-classical effects. Fundamental understanding of the properties of such a liquid requires an advanced form of quantum physics, and these very cold liquids are therefore termed quantum liquids ...  2, fiche 1, Anglais, - quantum%20liquid

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