Thermochemistry

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Thermochemistry Noun

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[thur-mo-kem-is-tree]

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Thermochemistry

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The branch of chemistry that studies the heat exchange associated with chemical reactions and physical transformations.

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Example: This diagram shows that heat energy naturally flows from a hotter object to a colder object, a fundamental principle in thermochemistry.

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System Noun

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[sis-tuhm]

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System

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The specific substance or process being studied and observed for energy changes within a thermochemical context.

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Example: This diagram shows a 'system' as the specific area of interest, separated from the 'surroundings' by a 'boundary,' which is essential for studying energy changes.

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Surroundings Noun

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[suh-round-ings]

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Surroundings

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Everything outside of a defined system that can exchange energy with it during a process.

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Example: In thermochemistry, the 'surroundings' is everything outside the 'system' being studied. The 'boundary' separates the system from its surroundings.

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Heat (q) Noun

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[heet]

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Heat (q)

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The transfer of thermal energy between a system and its surroundings that occurs due to a temperature difference.

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Example: This diagram shows the three ways heat energy transfers: radiation from the fire, convection through the moving water, and conduction up the pot's handle.

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Temperature Noun

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[tem-per-uh-cher]

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Temperature

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A quantitative measure of the average kinetic energy of the molecules or atoms within a substance.

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Example: This thermometer shows temperature, the measure of how hot or cold something is, by relating numerical values on its scale to different seasons.

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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 process that releases energy, typically in the form of heat, from the system to its surroundings.

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Example: A combustion reaction, like burning wood, is exothermic because it releases energy into the surroundings as heat and light.

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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 process that absorbs energy, typically in the form of heat, from the surroundings into the system.

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Example: The Earth absorbs energy from the Sun, which is an endothermic process because the planet is taking in heat from its surroundings.

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Enthalpy (ΔH) Noun

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[en-thal-pee]

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Enthalpy (ΔH)

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The total heat content of a system, often measured as the change (ΔH) during a reaction at constant pressure.

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Example: This diagram shows combustion, an exothermic reaction where fuel and oxygen react to release energy as heat, illustrating a negative change in enthalpy (ΔH).

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Thermochemical Equation Noun

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[thur-mo-kem-i-kuhl ee-kway-zhuhn]

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Thermochemical Equation

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A balanced chemical equation that explicitly includes the enthalpy change (ΔH) associated with the specified reaction.

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Example: This diagram shows how a thermochemical equation represents energy change: exothermic reactions release heat (ΔH < 0), and endothermic reactions absorb heat (ΔH > 0).

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Specific Heat (c) Noun

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[spuh-sif-ik heet]

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Specific Heat (c)

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The amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius.

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Example: This image shows that a substance with low specific heat (air in the empty pot) heats up faster than a substance with high specific heat (water).