Question

The melting point of a solid X is \[90^\circ C\] . What is the temperature on Kelvin Scale?

Answer 1

Hint: The quantised unit on the Celsius scale is equivalent to the quantised unit on the Kelvin scale. Just the point of origin of these two scales is different. It differs by a value of 273.15
Formula Used: \[^\circ C = K - 273.15\]

Complete step by step answer:
Consider the temperature measurement as a concept to be in the form of a number line. Now, we know that every number line has a negative part, a positive part and frame of reference for the positive and negative, i.e. zero. Now try to place the Celsius scale of measuring temperature such that \[0^\circ C\] is placed at the zero mark on the number line. This means that \[0^\circ C\] is now our point of reference.
Now, the unit value of both \[^\circ C\] and K is equal. But their placement on this number line is a bit different. Just as \[0^\circ C\] starts at the zero mark on the number line, the Kelvin scale starts at 273.15 in the negative direction of the number line. This indirectly means that zero kelvin (0 K) is equivalent to -273.15 \[^\circ C\].
Now, to derive a relation for converting Celsius to kelvin or vice versa, we can say that,
\[ - 273.15^\circ C\] = 0 K
\[^\circ C + 273.15\] = K
\[^\circ C\] = K – 273.15
For the given question, the value in Celsius is \[90^\circ C\]. Hence, substituting this in the above equation, we get,
\[\begin{array}{*{20}{l}}
  {90{\text{ }} = {\text{ }}K{\text{ }}-{\text{ }}273.15} \\
  {K{\text{ }} = {\text{ }}90{\text{ }} + {\text{ }}273.15} \\
  {K{\text{ }} = {\text{ }}363.15}
\end{array}\]

Hence, we can say that the melting point of the given solid in kelvin is 363.15 K

Note:
0 K is known as the absolute zero temperature because there has never been a temperature that has been recorded below this value. At this temperature, all the Kinetic energy of a substance is lost, and theoretically, it ceases to exist.