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Practice questions · Temperature scales

Add 273, or take it away.

Six original Cambridge-style questions on converting between Celsius and Kelvin, the meaning of absolute zero, and why a kelvin temperature can never be negative.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these fixed points in mind

T(K) = theta(C) + 273.

01
Calculation
[2 marks]

Convert the following temperatures:

(a) 80 degrees C into kelvin, [1] (b) 350 K into degrees Celsius. [1]

(a) 80 + 273 = 353 K

(b) 350 - 273 = 77 degrees C

02
[2 marks]

State the value of absolute zero in degrees Celsius, and write the equation used to convert a Celsius temperature to a Kelvin temperature.

  • Absolute zero = -273 degrees C. ✓
  • T (in K) = theta (in degrees C) + 273. ✓
03
[2 marks]

Describe what happens to the motion and energy of the particles of a substance as its temperature is lowered towards absolute zero.

  • The particles move more and more slowly. ✓
  • At absolute zero they have the least possible kinetic energy (effectively stop moving). ✓
04
Analysis
[2 marks]

Explain why it is not possible for a substance to have a temperature below 0 K.

  • At 0 K the particles already have the minimum possible energy. ✓
  • They cannot lose any more energy or move any more slowly, so no lower temperature is possible. ✓
05
Calculation
[2 marks]

On a cold night the temperature is -23 degrees C. A warm room is at 27 degrees C. Convert both temperatures to kelvin.

Cold: -23 + 273 = 250 K

Warm: 27 + 273 = 300 K

06
Analysis
[2 marks]

A student converts a temperature and writes the answer as -15 K. Without knowing the original temperature, explain how you can tell this answer must be wrong.

  • Kelvin temperatures cannot be negative, because 0 K (absolute zero) is the lowest possible temperature. ✓
  • A value of -15 K is below absolute zero, which is impossible, so the student has made an error. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.