scientist with beakers
Thermodynamic stability is a term used in chemistry to describe a chemical system that neither consumes nor releases thermal energy. In the absence of thermal energy change, the substance does not undergo any chemical reaction and is therefore stable. In mixtures that are thermodynamically stable, the steady state occurs before any of the chemical reactants change into chemical products or after the process is complete. If a chemical system is thermodynamically stable, there is no movement of heat within a system or between a system and its surrounding environment.
Scientists can measure the amount of thermal energy produced or put into a chemical reaction. Some chemical systems will automatically react with each other when they come into contact. Thermodynamic reactions that occur spontaneously and release heat are known as exothermic reactions. While it is possible to add thermal energy to this type of system, an act that often works to speed up the reaction, there is enough energy within the reactants to convert them to products. After the reaction is complete, the chemical, which is the same chemical system that once made up the reactants, is considered to be in a state of thermodynamic stability.
Reactants may need to consume energy to transform into products. In these types of chemical systems, thermodynamic stability occurs before energy is added to the system. In the absence of additional thermal energy, the chemicals in the system do not react with each other. They are able to resist transformation into products. This type of thermodynamic stability occurs in endothermic reactions.
An example of an exothermic chemical reaction that results in a thermodynamically stable product is the transformation of sugar and water into sugar water. When sugar is added to water, the reactants form a thermodynamically unstable system. The sugar automatically begins to dissolve in the water, a process that continues until all the sugar is used up. At this point, the system is thermodynamically stable because energy would need to be added to the system to reverse the chemical process and separate the water and sugar from each other. True states of thermodynamic stability are rare because chemical systems are almost always in the process of reacting in some way.