Consider three systems A, B and C that can be thermally isolated from their surroundings. When A is placed in contact with C, no measurable heat exchange is observed. The same absence of heat exchange is noticed when B is separately placed in contact with C under identical conditions.
(i) Construct a logical argument to prove that, under these conditions, no heat exchange will occur when A and B are brought into mutual contact.
(ii) Explain how this result underpins the use of thermometers for routine temperature measurements.
(iii) State two experimental precautions necessary to ensure the validity of such temperature comparisons in practice.