National League for Nursing (NLN PAX) Practice Exam

Which of these temperatures is known as Absolute Zero?

1. 0°C

2. 0 K

3. positive 273°C

4. negative 273 K

The correct answer is: 0 K

Absolute Zero is defined as the temperature at which the entropy of a perfect crystal approaches zero, and molecular motion is theoretically at a minimum. This temperature is established as 0 Kelvin (K), which is equivalent to -273.15 degrees Celsius. In the Kelvin scale, temperatures start at absolute zero, and there are no negative values. Therefore, the designation of 0 K reflects this fundamental limit of temperature, marking the point where thermal energy is absent. The other choices represent temperatures that do not correspond to absolute zero. For example, 0°C is the freezing point of water, significantly above absolute zero. A positive 273°C indicates a high temperature far away from the extreme cold of absolute zero. Meanwhile, negative 273 K is also inaccurate, as the Kelvin scale does not extend into negative values, affirming that 0 K is the true representation of absolute zero.