What is meant by a temperature of absolute zero?

• A. The temperature at which all molecular movement stops.
• B. The highest possible temperature.
• C. The temperature where water boils at sea level.
• D. The temperature at which gas pressure becomes zero.

Answer: (A)

Absolute zero is the thermodynamic zero of temperature: 0 Kelvin, which is -273.15°C. It represents the point where thermal energy is minimized as far as physics allows, so, in simple terms, the random motion of particles would stop. In practice, quantum effects mean some motion remains (zero-point energy), but you can’t remove any more thermal energy beyond this limit. That’s why the statement describing it as the temperature at which all molecular movement stops captures the essential idea, even though it’s a simplified view. The other ideas don’t define absolute zero: it isn’t the highest temperature, it isn’t the boiling point of water at sea level, and while pressure would drop toward zero as temperature approaches absolute zero for a fixed amount of gas, the defining feature is the temperature value itself, not the pressure.