Heat capacity and entropy are two sides of the same coin. They are closely related scientific concepts that are interdependent and can be studied in relation to one another. Heat capacity is a measurable concept whereas entropy is more abstract.
Heat Capacity vs Entropy
The main difference between heat capacity and entropy is that while heat capacity is dependent on the material or object, like measuring the change in its temperature when the material absorbs energy, entropy, on the other hand, does not rely on any object. Entropy counts the number of specific states that the system can be found in, given the thermodynamic parameters known.
Heat capacity refers to the physical property of matter that is attributed to the amount of heat imparted to an object that further results in a difference in the temperature of the said object by a unit. Heat capacity is also known as thermal capacity. Joule per kelvin, commonly written as J/K, is recognized as the heat or thermal capacity’s official SI.
Entropy is defined as a thermodynamic quantity that is used to represent the amount of thermal energy of a given system that is not feasible for converting it into any kind of productive work. It is a scientific concept that is used in calculating and observing the uncertainty, disorder, randomness, or chaos that can be seen in a system. The concept of entropy helps study the direction of spontaneous change. Entropy is widely used to analyze common phenomena.
Comparison Table Between Heat Capacity and Entropy
| Parameters of Comparison | Heat Capacity | Entropy |
| Meaning | It refers to the change in the temperature of an object. This change is a result of the energy absorbed. | It is the counting of the specific systems that a material can be found under, given the known thermodynamic parameters. |
| Dependency | Both material and process-dependent, it measures the change in temperature of the object and can be both reversible and irreversible. | Independent of any object or material, most processes are, however, irreversible, making them process-dependent. |
| Value | An absolute value of heat capacity can be determined via experimentation | The absolute value of entropy cannot be determined. However, entropy can be expressed using relative values. |
| Relation | Heat capacity is the rate of change of entropy with temperature. | Entropy is calculated as the cumulative filling of energy destinations between absolute zero (motionless) and a given temperature. |
| Calculation | Q= mcΔT Q = heat energy m = mass c = specific heat capacity ΔT = change in temperature | S= kblnΩ S = entropy kb = Boltzmann constant ln = natural logarithm Ω = number of microscopic configurations |
What is Heat Capacity?
Heat capacity measures the difference in temperature of an object or material when energy is absorbed or imparted by the material. It is the property of matter that is physical in nature calculating the amount of energy that the above-mentioned object must absorb for it to produce a change in its core temperature by a single unit.
Heat capacity is studied to be an extensive property. The value of heat that has to be added or introduced to the given object or material to raise its temperature varies according to the initial temperature of the product in question and the amount of pressure that is applied. The amount of heat to be added also varies with the phase transitions such as vaporization or melting.
The process of finding heat capacity is rather simple for any given object. the object is first measured and slowly a specific amount of heat is introduced to it and observed for the temperature to become uniform again. later, the change in the temperature is measured and noted. This method of attempting to calculate the heat capacity of material works best for gases and offers less precise measurements in the case of solids.
The SI unit is joule per kelvin or alternatively J/K or J⋅K−1, for heat capacity. The heat capacity of any given object is the amount of energy divided by a temperature change.
What is Entropy?
Entropy is a scientific concept that can be studied as a physical measurable property. It is defined as the quantitative measure of randomness, disorder, or chaos in any given system. Located under thermodynamics, this concept deals with the transfer of heat energy within a system.
Entropy is pivotal and plays a key role in the second law of thermodynamics. Referred to by Scottish scientist and engineer Macquorn Rankine in 1850, the concept of thermodynamics was named in a variety of different ways such as thermodynamic function and heat-potential. Instead of some form of “absolute entropy,” physicists study the change in entropy that occurs in a specific thermodynamic process.
The entropy change is material-independent and process-dependent as certain processes are irreversible or impossible. It has been observed that the entropy change is proportional to the heat transfer in a reversible process (at constant temperature). However, most processes are irreversible, so the quantity is process-dependent.
The entropy counts the number of specific states that the system can be found in, given the thermodynamic parameters known. Entropy can be studied via two different approaches, namely, the macroscopic and microscopic perspectives of classical thermodynamics and statistical mechanics, respectively.
Main Differences Between Heat Capacity and Entropy
- The difference between heat capacity and entropy is that while heat capacity is dependent on the material or object, like measuring the change in its temperature when the material absorbs energy, entropy, on the other hand, does not rely on any object.
- Entropy counts the number of specific states that the system can be found in, given the thermodynamic parameters known, whereas heat capacity measures the degree change in temperature.
- Heat capacity is both material and process dependent. Entropy is material-independent and process-dependent.
- Heat capacity is the rate of change of entropy with temperature. Entropy is a known scientific concept that measures the syestem in question’s thermal energy for an unit that is unavailable for any work of effect.
- Heat capacity has an absolute value whereas entropy does not have an absolute value.
Conclusion
The terms heat capacity and entropy are related to each other. While heat capacity measures the change or difference in the given object’s temperature by the degree or level of energy absorbed by the object in order to produce one unit change of temperature, entropy by itself cannot be measured and hence, is not of much use.
Heat capacity can be measured for any object in the SI unit J/K and the absolute value discovered via experimenting can be used. Entropy is defined as a thermodynamic quantity that is used to represent the amount of thermal energy of a given system that is not feasible for converting it into any kind of productive work. This is taken as the degree of disorder or randomness in the system. The changes in entropy, that is how it differs from one state to the other, are made use of to study everyday phenomena.
Heat capacity is material-dependent and process-independent. Entropy is material-independent and the change in entropy is proportional to the transfer of heat in a reversible process, however, most processes are irreversible. Therefore, it is process-dependent.
References
- https://pubs.acs.org/doi/pdf/10.1021/ja01298a023
- https://newbedev.com/difference-between-heat-capacity-and-entropy