Thermodynamics is the branch of study to establish the relationship between heat and work. There are various terms and laws which are applicable to the heat and energy. Enthalpy and entropy are the very frequent terms used in thermodynamics. We need to be familiar with the related laws of thermodynamics, in order to understand their relationship. Here we will have the major difference between Enthalpy and Entropy in a systematic way. In simple terms, enthalpy is represented as the total heat content, on the other hand, entropy is the degree of disorder.
What is Enthalpy?
Enthalpy is representing the heat content of a system. It is a common fact that the heat can go in or out of the system. So, in a chemical reaction, the change of heat is defined as enthalpy change. This knowledge about the increase or decrease of the enthalpy of the system during a chemical reaction is a very crucial factor for understanding the reaction. Also, the change in the enthalpy of the system during a chemical reaction is termed as the sum total value of change in its internal energy and the change in the product of the pressure and volume of the system.
What is Entropy?
Any type of medium either solid or fluid always consists of molecules. The measurement of the randomness of molecules in the system is called entropy. Therefore, if the randomness of molecules is more, then there will be more increase in entropy of the process. And as a result, the percentage of heat which may be converted into work will be less. Thus, we may say that entropy is a function of the quantity of heat.
Similarly, if the randomness of molecules is less, then the increase in entropy will also be less. Due to this, the entropy of solid is less than the entropy of gases. It is because those gases are having more random molecules than the solid. The entropy of the system with its surroundings combined will always increase. Thus entropy of the universe always increases.
Difference between Enthalpy and Entropy
difference between enthalpy and entropy
The important difference between enthalpy and entropy
| Parameter | Enthalpy | Entropy |
| Nature | It is a kind of energy. | It is the property of the matter. |
| Definition | It is the sum total of the internal energy and energy flow. | It is the scientific measurement of the randomness of molecules. |
| System tendency | The natural system always favors the minimum enthalpy. | The natural system favors maximum entropy. |
| Nomenclature | This term was given by scientist Heike Kamerlingh Onnes. | This term was given by scientist Rudolf Clausius. |
| Standardization | It is applicable to the related standard conditions. | It does not have any specified limit or condition. |
| Unit of measurement | It unit is Joule per mol. | It unit is Joule per Kelvine. |
| Symbol | Its symbol is H. | Its symbol is S. |
The Laws of the Thermodynamics:
To get a better understanding of the difference between enthalpy and entropy, let us have the laws of thermodynamics. The popular law of conservation of energy, states that when the heat is added to a system, then it transforms to an equal amount of energy of some other form. It is possible by doing either by increasing the amount of internal energy within the system, or by doing external work by leaving the system, or both of these,
The measurement of the energy in a thermodynamic system is termed as enthalpy. Since the total enthalpy of a system is not possible to measure directly. Therefore, scientists always measure the change in enthalpy of the system.
According to the second law of thermodynamics, no reaction is completely efficient and hence heat is always transferred from warmer objects to colder objects. This law is also termed as the law of disorder, as it describes the concept of entropy. The energy available in the system is inherently active and will act spontaneously to or minimize the thermodynamic forces. Thus more energy present in a system will represent more disorder. When a substance changes its state from a solid to a liquid to gas then molecules will have more freedom to move at each new stage.
FAQs about enthalpy and entropy:
Q.1: Give one sentence for clarifying the difference between enthalpy and entropy.
Solution: Entropy is to measure the randomness of activity in a system, on the other hand, enthalpy is the measurement of the overall amount of energy in the system.
Q.2: Find the true statement the following with explanation.
(a) The enthalpy of liquid water is nonzero whereas enthalpy of hydrogen gas is zero.
(b) The entropy of liquid water is higher than the entropy of hydrogen gas.
(c) Both of these are true.
(d) None of these are true
Solution: The first statement is true. Therefore option (a) is correct. Enthalpy will be zero for the elemental compounds like hydrogen gas and oxygen gas. So, enthalpy will be nonzero for water. On the other hand, entropy is always the highest for gases. This is because gas molecules are widely dispersed and hence more disordered. So, hydrogen gas will have higher entropy than liquid water.
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