The lowest possible temperature, 0 K or -273.15 degrees Celsius, where particle motion is minimal.
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Absolute zero is the lowest possible temperature, defined as 0 K, which equals -273.15°C. At this temperature a classical particle would have no thermal motion, and a quantum system retains only its zero-point energy. The third law of thermodynamics states that absolute zero cannot be reached in a finite number of steps, although temperatures within billionths of a kelvin have been achieved. The kelvin scale starts at absolute zero, so the conversion is K = °C + 273.15. Because temperature in kelvin is proportional to average molecular kinetic energy, zero kelvin is the natural reference point for the gas laws.
Key ideas: Conversions: T(K) = t(C) + 273.15; a change of 1 K equals a change of 1 C. Gas thermometers extrapolate to this value, and modern cryogenics reaches nanokelvin through laser and evaporative cooling. Liquid helium boils at 4.2 K and nitrogen at 77 K, both far above absolute zero.
Common mistakes and connections: Students think particles stop completely at 0 K, but quantum zero-point motion remains. Another error is expecting real gases to follow Charles's law down to 0 K when they liquefy. Negative kelvin temperatures are not colder than absolute zero. Linked to the third law of thermodynamics, entropy of a perfect crystal and superconductivity.
Extrapolating volume against temperature for any gas reaches zero at -273.15 C, which defines absolute zero (0 K), the lowest possible temperature. The interactive lesson shows this as a live animation or chart.
Helium remains a liquid at low temperatures under normal pressure because its zero-point energy prevents it from freezing.
The lowest possible temperature, 0 K or -273.15 degrees Celsius, where particle motion is minimal.
Absolute Zero is a beginner topic in States of Matter & Solutions. It needs no earlier chemistry lessons and is a good starting point.
Study these earlier topics in States of Matter & Solutions first: Combined Gas Law, Ideal Gas Law, Gas Constant.
The next topics in States of Matter & Solutions are Dalton's Law of Partial Pressures and Mole Fraction.
Yes. The interactive lesson includes a self-check question on Absolute Zero, and the States of Matter & Solutions quiz draws on every topic in this area.
Absolute Zero is topic 15 of 109 in States of Matter & Solutions.