Entropy

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Thermodynamics Noun

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[thur-mo-dy-nam-iks]

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Thermodynamics

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The branch of science concerned with heat, temperature, and their relationship to energy, work, and chemical reactions.

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Example: This diagram shows that as a solid is heated (high temperature), its particles vibrate more and spread apart, becoming more disordered (higher entropy).

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Enthalpy Noun

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[en-thal-pee]

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Enthalpy

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A thermodynamic quantity representing the total heat content of a system, often measured as the change during a reaction.

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Example: Adding heat energy (enthalpy) causes water to change state from solid ice to liquid water, and then to gaseous vapor, increasing its total heat content.

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Exothermic Adjective

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[ek-so-thur-mik]

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Exothermic

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Describes a chemical reaction or process that releases energy from the system to its surroundings, typically as heat.

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Example: A combustion reaction, like burning wood, is exothermic because it releases energy as heat and light, while also increasing entropy by creating disordered gases.

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Endothermic Adjective

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[en-do-thur-mik]

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Endothermic

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Describes a chemical reaction or process that absorbs energy from its surroundings, usually in the form of heat.

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Example: The Earth absorbs energy from the Sun, an endothermic process that warms the planet and drives weather, which increases overall disorder (entropy).

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Entropy Noun

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[en-tro-pee]

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Entropy

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A thermodynamic measure of the dispersal, randomness, or disorder of matter and energy within a given system.

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Example: The image shows that entropy increases as particles in a system move from an ordered, structured arrangement (low entropy) to a random, disordered arrangement (high entropy).

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Microstates Noun

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[my-kro-stayts]

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Microstates

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The specific, detailed microscopic configurations of particles that correspond to a single macroscopic state of a thermodynamic system.

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Example: This diagram shows that for a general state (macrostate), like getting one heads and one tails, there can be multiple specific arrangements (microstates) to achieve it.

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System Noun

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[sis-tem]

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System

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In thermodynamics, the specific portion of the universe that is being studied, distinct from its external surroundings.

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Example: In science, a system is the specific part of the universe being studied, separated from everything else (the surroundings) by a boundary.

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Spontaneous Reaction Noun

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[spon-tay-nee-us ree-ak-shun]

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Spontaneous Reaction

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A chemical reaction that proceeds in a given set of conditions without the need for continuous external energy input.

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Example: Mixing iron and hydrochloric acid causes a chemical reaction that produces gas bubbles on its own, showing a process that happens spontaneously without continuous energy input.

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Nonspontaneous Reaction Noun

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[non-spon-tay-nee-us ree-ak-shun]

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Nonspontaneous Reaction

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A chemical reaction that cannot occur on its own and requires a continuous input of external energy to proceed.

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Example: This diagram shows that an external energy source, a battery, is required to force water to split into hydrogen and oxygen gases.

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Reversibility Noun

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[ri-vur-suh-bil-i-tee]

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Reversibility

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The property of a process that can proceed in either the forward or backward direction, returning to its original state.

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Example: This diagram shows a pendulum swinging back and forth, an example of a reversible process where the motion can be reversed to its starting point.