Reaction Spontaneity

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Spontaneous Process Noun

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[spon-tay-nee-us pro-sess]

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Spontaneous Process

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A physical or chemical change that, once begun, occurs with no outside intervention under a given set of conditions.

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Example: The reaction between acid and iron starts on its own and produces gas bubbles, showing a process that happens without continuous external energy input.

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Nonspontaneous Process Noun

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[non-spon-tay-nee-us pro-sess]

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Nonspontaneous Process

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A process that requires a continuous input of external energy to occur and will not happen on its own.

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Example: The arrows pointing into the test tube show that energy must be constantly added from the outside to make this chemical process happen.

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Enthalpy (ΔH) Noun

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[en-thal-pee]

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Enthalpy (ΔH)

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A thermodynamic property of a system that measures its total heat content, often describing heat changes in chemical reactions.

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Example: This diagram shows that energy (represented by Δ) must be added to change ice to water and water to vapor, illustrating how enthalpy (a system's heat content) increases.

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Entropy (S) Noun

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[en-truh-pee]

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Entropy (S)

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A measure of the disorder, randomness, or the number of possible ways the energy of a system can be distributed.

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Example: Particles in an ordered arrangement have low entropy (less disorder), while particles in a random, spread-out arrangement have high entropy (more disorder).

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Change in Entropy (ΔS) Noun

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[cheynj in en-truh-pee]

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Change in Entropy (ΔS)

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The change in the disorder or randomness of a system, calculated as the final entropy minus the initial entropy.

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Example: This image shows water changing from a solid (ice) to a liquid and then to a gas (steam) as heat is added, illustrating an increase in disorder (entropy).

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Second Law of Thermodynamics Noun

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[sek-und law uv thur-mo-dy-nam-iks]

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Second Law of Thermodynamics

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The principle stating that spontaneous processes always proceed in a way that increases the total entropy of the universe.

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Example: This diagram shows that heat energy spontaneously flows from a hot object to a cold object, a core principle of the Second Law of Thermodynamics.

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System Noun

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[sis-tum]

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System

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In thermodynamics, the specific part of the universe, such as a reaction or process, that is being studied.

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Example: In science, the 'system' is the part we are studying (like a chemical reaction), separated from the 'surroundings' by a 'boundary'.

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Surroundings Noun

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[suh-roun-dings]

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Surroundings

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In thermodynamics, everything in the universe that exists outside of the system being studied.

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Example: This diagram shows that the 'surroundings' is everything outside a defined 'system', and together they make up the 'universe' in a scientific context.

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Gibbs Free Energy (G) Noun

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[gibz free en-er-jee]

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Gibbs Free Energy (G)

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A thermodynamic quantity representing the energy in a system that is available to do useful work at constant temperature.

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Example: This image shows that pushing a boulder uphill requires a lot of energy, just like a non-spontaneous chemical reaction (positive Gibbs Free Energy) needs energy to happen.

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Free Energy Change (ΔG) Noun

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[free en-er-jee cheynj]

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Free Energy Change (ΔG)

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The change in Gibbs free energy during a reaction, which indicates whether the reaction is spontaneous or nonspontaneous.

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Example: This image shows a ball rolling downhill, a spontaneous process. It represents a reaction moving from a high-energy state to a stable, low-energy state, releasing free energy.