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A ball rolling down an incline is an example of a spontaneous process. Richard Kolker / Getty Images Updated on November 27, 2019 In a system, be it chemistry, biology, or physics, there are spontaneous processes and nonspontaneous processes. Definition of a Spontaneous ProcessA spontaneous process is one that occurs on its own, without any energy input from the outside. For example, a ball will roll down an incline; water will flow downhill; ice will melt into water; radioisotopes will decay; and iron will rust. No intervention is required because these processes are thermodynamically favorable. In other words, the initial energy is higher than the final energy. Note that how quickly a process occurs has no bearing on whether or not it is spontaneous: It may take a long time for rust to become obvious, yet it will develop when iron is exposed to air. A radioactive isotope may decay instantly or after millions or even billions of years; yet, it will decay. Spontaneous Versus NonspontaneousThe reverse of a spontaneous process is a nonspontaneous process: Energy must be added in order for one to occur. For example, rust doesn't convert back into iron on its own; a daughter isotope won't return to its parent state. Gibbs Free Energy and SpontaneityThe change in Gibbs free energy or the Gibbs function may be used to assess the spontaneity of a process. At constant temperature and pressure, the Gibbs equation is ΔG = ΔH - TΔS, in which ΔH is the change in enthalpy, ΔS is the change in entropy, and ΔG is the amount of free or available energy. As for the results:
spontaneities
The state or quality of being spontaneous. Spontaneous behavior, movement, action, etc. Spontaneity is defined as the act or quality of acting without thinking in advance. Going on a road trip at the very last minute because it seems fun is an example of spontaneity. (biology) The tendency to undergo change, characteristic of both animal and vegetable organisms, and not restrained or checked by the environment. (biology) The tendency to activity of muscular tissue, including the voluntary muscles, when in a state of healthful vigour and refreshment. Other Word Forms of SpontaneityNounOrigin of Spontaneity
Find Similar WordsFind similar words to spontaneity using the buttons below. Words Starting WithWords Ending WithWords Starting With S and Ending With YWord LengthWords Near Spontaneity in the DictionaryNitroglycerin is a tricky substance. An active ingredient in dynamite (where it is stabilized), "raw" nitroglycerin is very unstable. Physical shock will cause the material to explode. The reaction is shown below. \[4 \ce{C_3H_5(ONO_2)_3} \rightarrow 12 \ce{CO_2} + 10 \ce{H_2O} + 6 \ce{N_2} + \ce{O_2}\nonumber \] The explosion of nitroglycerin releases large volumes of gases and is very exothermic. Spontaneous ReactionsReactions are favorable when they result in a decrease in enthalpy and an increase in entropy of the system. When both of these conditions are met, the reaction occurs naturally. A spontaneous reaction is a reaction that favors the formation of products at the conditions under which the reaction is occurring. A roaring bonfire is an example of a spontaneous reaction, since it is exothermic (there is a decrease in the energy of the system as energy is released to the surroundings as heat). The products of a fire are composed partly of gases such as carbon dioxide and water vapor. The entropy of the system increases during a combustion reaction. The combination of energy decrease and entropy increase dictates that combustion reactions are spontaneous reactions.  A nonspontaneous reaction is a reaction that does not favor the formation of products at the given set of conditions. In order for a reaction to be nonspontaneous, it must be endothermic, accompanied by a decrease in entropy, or both. Our atmosphere is composed primarily of a mixture of nitrogen and oxygen gases. One could write an equation showing these gases undergoing a chemical reaction to form nitrogen monoxide: \[\ce{N_2} \left( g \right) + \ce{O_2} \left( g \right) \rightarrow 2 \ce{NO} \left( g \right)\nonumber \] Fortunately, this reaction is nonspontaneous at normal temperatures and pressures. It is a highly endothermic reaction with a slightly positive entropy change \(\left( \Delta S \right)\). Nitrogen monoxide is capable of being produced at very high temperatures and has been observed to form as a result of lightning strikes. One must be careful not to confuse the term spontaneous with the notion that a reaction occurs rapidly. A spontaneous reaction is one in which product formation is favored, even if the reaction is extremely slow. A piece of paper will not suddenly burst into flames, although its combustion is a spontaneous reaction. What is missing is the required activation energy to get the reaction started. If the paper were to be heated to a high enough temperature, it would begin to burn, at which point the reaction would proceed spontaneously until completion. In a reversible reaction, one reaction direction may be favored over the other. Carbonic acid is present in carbonated beverages. It decomposes spontaneously to carbon dioxide and water, according to the following reaction. \[\ce{H_2CO_3} \left( aq \right) \rightleftharpoons \ce{CO_2} \left( g \right) + \ce{H_2O} \left( l \right)\nonumber \] If you were to start with pure carbonic acid in water and allow the system to come to equilibrium, more than \(99\%\) of the carbonic acid would be converted into carbon dioxide and water. The forward reaction is spontaneous because the products of the forward reaction are favored at equilibrium. In the reverse reaction, carbon dioxide and water are the reactants, and carbonic acid is the product. When carbon dioxide is bubbled into water, less than \(1\%\) is converted to carbonic acid when the reaction reaches equilibrium. The reverse reaction, as written above, is not spontaneous. Summary
What are examples of spontaneous reactions?A roaring bonfire is an example of a spontaneous reaction, since it is exothermic (there is a decrease in the energy of the system as energy is released to the surroundings as heat). The products of a fire are composed partly of gases such as carbon dioxide and water vapor.
What is spontaneity in a reaction?A spontaneous reaction is one in which product formation is favored, even if the reaction is extremely slow. You do not have to worry about a piece of paper on your desk suddenly bursting into flames, although its combustion is a spontaneous reaction.
How do you determine spontaneity?The temperature can be the deciding factor in spontaneity when the enthalpy and entropy terms have opposite signs: If ΔH is negative, and –TΔS positive, the reaction will be spontaneous at low temperatures (decreasing the magnitude of the entropy term).
What are the two factors of spontaneity?Thus, Enthalpy and Entropy are the two factors that tell about the spontaneity of a reaction.
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What is an example of spontaneity?
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