The Fundamental Difference Between Entropy and Enthalpy
Thermodynamics is the study of heat and energy transfers, and two key concepts in it are entropy and enthalpy. Though these two concepts might sound similar, they are fundamentally different from each other. In this article, we will discuss the differences between entropy and enthalpy.
What is Entropy?
Entropy is a measure of the randomness or disorder in a system. The more disordered the system, the higher its entropy. It is represented by the symbol S and is measured in units of J/K (joules per kelvin). Entropy also tells us about the direction of energy transfer in a process. A spontaneous process will always result in an increase in the entropy of the system.
For example, when you drop a glass, it shatters into many pieces. This is an increase in the randomness or disorder of the system, which means an increase in entropy.
What is Enthalpy?
Enthalpy, on the other hand, is a measure of the total energy of a system. It is represented by the symbol H and is measured in units of J (joules). Enthalpy takes into account the internal energy of a system, as well as any work performed by or on the system.
Enthalpy is particularly important in thermochemistry, which deals with the heat and energy transfers involved in chemical reactions. During a chemical reaction, the enthalpy change tells us how much heat or energy was gained or lost by the system.
The Key Differences
The main difference between entropy and enthalpy is that entropy is a measure of the disorder of a system, whereas enthalpy is a measure of the energy in a system. The entropy of a system is related to randomness, whereas enthalpy is related to energy.
As stated above, spontaneous processes increase entropy, whereas enthalpy change in a reaction tells us whether it is exothermic or endothermic. Another difference is that entropy is always positive, whereas enthalpy can be positive or negative.
Conclusion
In conclusion, while entropy and enthalpy might appear similar at first glance, they are fundamentally different from each other. Entropy measures the disorder or randomness of a system, while enthalpy measures the total energy of a system. Understanding these two concepts is essential to understanding the fundamentals of thermodynamics.
Table difference between entropy and enthalpy
| Entropy | Enthalpy |
|---|---|
| Entropy is a measure of randomness or disorder in a system. | Enthalpy is a measure of the total energy of a system. |
| It is often represented by the symbol S. | It is often represented by the symbol H. |
| Entropy increases with an increase in disorder or randomness in a system. | Enthalpy changes occur due to changes in the internal energy, volume, and pressure of a system. |
| It is a thermodynamic property that is measured in units of joules per Kelvin. | It is also a thermodynamic property that is measured in units of energy, such as joules or calories. |
| It can be calculated as ΔS = Qrev/T, where ΔS is the change in entropy, Qrev is the reversible heat transferred, and T is the temperature. | It can be calculated as ΔH = ΔU + PΔV, where ΔH is the change in enthalpy, ΔU is the change in internal energy, P is the pressure, and ΔV is the change in volume. |
| Entropy is related to the degree of disorder or randomness in a system. | Enthalpy is related to the amount of heat energy released or absorbed in a reaction. |