It is shown that the equations describing the heating of a system by heat exchange and by compression are asymmetric; in the equation for the latter, there is a term that describes the heat loss, whereas  this term is absent from the equation for the former. It is shown that this term is redundant and must be omitted. The calculation of heat loss during compression must be done differently than previously supposed, in agreement with the previous findings of the author. Data for the substances with negative thermal expansion and negative compressibility prove this result.

heat exchange, adiabatic heating, internal energy, negative thermal expansion, negative compressibility, heat of phase transitions, first law of thermodynamics, ideal gas.