Question

Why is \[ - 273^\circ C\] called absolute zero?

Answer 1

Hint: Temperature is a measure of how fast or slow atoms are moving within a substance or the average kinetic energy of those particles. It is the measurement of hotness or coldness of the body.

Complete step by step answer:
 Kelvin scale is the absolute scale used to record the temperature. Zero kelvin is the lowest possible temperature and called absolute zero. Conversion of kelvin into Celsius can be done by the formula: \[C = K - 273.15\].
Absolute zero is the lowest possible temperature where nothing can be colder and no heat remains in a substance i.e. a point at which the fundamental particles have minimum vibrations. It is defined precisely as 0 K on the kelvin scale, which is an absolute thermodynamic temperature scale, \[ - 273^\circ C\]on the Celsius scale and -459.67 degrees F on the Fahrenheit scale.
At this temperature, the particles in a substance are essentially motionless, so there can be no lower temperature than this. The system reaches its lowest possible energy or thermal motion at absolute zero. At such temperatures water begins to freeze, its molecular movement comes to rest which do not happen at zero degree Celsius.
If absolute zero is 0 K, then using this formula,\[C = K - 273.15\], it is the same as \[ - 273^\circ C\]. Hence, \[ - 273^\circ C\] is called absolute zero.

Note:
Absolute zero is impossible to reach. The reason is that the amount of work necessary to remove heat from a substance to achieve absolute zero is infinite, which is hard to get. Also, according to quantum mechanics, atoms and molecules always have some irreducible motion.