Final answer:
Heat capacity is the heat required to raise the temperature of a substance by one degree Celsius, while specific heat capacity is the heat required for unit mass of a substance. Molar specific heat capacities at constant volume and pressure are defined for one mole of a substance under constant volume or pressure conditions, respectively.
Step-by-step explanation:
Understanding Heat Capacity
The concept of heat capacity is critical in the study of thermodynamics and can be defined in several related ways:
- Specific heat capacity, often simply called specific heat, is defined as the amount of heat required to change the temperature of a unit mass of a substance by one degree Celsius. Specific heat capacity is an intensive property, meaning it does not depend on the mass of the substance. The equation Q = mcΔT represents the heat (Q) added or removed, the mass (m) of the substance, the specific heat capacity (c), and the change in temperature (ΔT). Specific heat capacity has units of J/kg/°C.
- Heat capacity is the amount of heat required to raise the temperature of a substance by one degree Celsius, regardless of the mass. It is an extensive property, meaning it directly depends on the amount of the substance; for example, if you double the mass, you double the heat capacity. Heat capacity is typically expressed in J/°C.
- The molar specific heat capacity at constant volume (Cv) and at constant pressure (Cp) refer to the amount of heat required to raise the temperature of one mole of a gas by one degree Celsius, with the volume or pressure held constant, respectively. Cv and Cp are specific to the state of the substance (solid, liquid, or gas), with gases showing a significant difference between values at constant volume and at constant pressure. The units for molar specific heat capacity are J/(mol•°C).
These concepts are essential for understanding heat transfer in physical systems and differ based on whether the system's volume or pressure is held constant during the heat addition or removal.