Answer – At a temperature of 250 K (–23°C) and constant pressure, the specific heat of air is 1003 J/kg.K; however, when volume is constant at the same temperature, the specific heat of air changes to 716 J/kg.K.

Explanation: 

Specific heat is the amount of heat needed to increase the temperature of a unit mass of a substance by a unit temperature. Its SI unit is joules per kilogram per Kelvin (J/kg⋅K). It may also be measured in joules per kilogram per degree Celsius (J/kg⋅°C), joules per gram per degree Celsius (J/g⋅°C), or calories.

It is closely related to the heat capacity of a substance, which can be the same as specific heat when it does not depend on mass.

The specific heat of any substance is directly proportional to its temperature. Further, every gas has two specific heat values: one for constant volume (Cᵥ) and one for constant pressure (Cₚ). Thus, the specific heat of air increases with an increase in temperature and has different values at constant volume and constant pressure.

• At constant pressure and a temperature of 250 K (–23°C), the specific heat of air, or Cₚ of air, is 1003 J/kg.K.
• At constant pressure and a temperature of 300 K (27°C), the specific heat of air, or Cₚ of air, is 1005 J/kg.K. 

• At constant volume and a temperature of 250 K (–23°C), the specific heat of air, or Cᵥ of air, is 716 J/kg.K.
• At constant volume and a temperature of 300 K (27°C), the specific heat of air, or Cᵥ of air, is 718 J/kg.K.

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