Thermochemistry Vocab
| Term | Definition |
|---|---|
| calorie | The amount of heat required to raise the temperature of one gram of pure water by 1*C |
| calorimeter | An insulated device that is used to measure the amount of heat released or absorbed during a physical or chemical process |
| chemical potential energy | The energy stored in a substance because of its composition / bonds, usually released or absorbed as heat during physical or chemical processes |
| energy | The capacity to do work or produce heat |
| enthalpy | The heat content of a system at constant pressure |
| enthalpy (heat) of combustion | The enthalpy change (ΔH) for the complete burning of one mole of a substance |
| enthalpy (heat) of reaction | The enthalpy change (ΔH) for a reaction; reflected by the difference in the heat content of the products versus the reactants |
| heat | A form of energy that flows from a warmer object to a cooler object |
| Hess’s law | States that if two or more thermochemical equations can be added to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is equal to the enthalpy change for the final reaction |
| joule | The SI unit of heat and energy; abbreviated as J; 1000 J = 1 kJ |
| molar enthalpy (heat) of fusion | The amount of heat required to melt one mole of a solid substance |
| molar enthalpy (heat) of vaporization | The amount of heat required to evaporate one mole of a liquid |
| specific heat | The amount of heat required to raise the temperature of one gram of any substance by 1oC. |
| standard enthalpy (heat) of formation | The change in enthalpy (ΔH) that is caused by the formation of one mole of a compound in its standard state from its elements in their standard states. |
| surroundings | Includes everything in the universe except the system being studied |
| system | The specific part of the universe containing the reaction or process being studied, as defined by the observer |
| thermochemical equation | A balanced chemical equation that includes the physical states of all substances and the energy change, usually expressed as change in enthalpy (ΔH) |
| thermochemistry | The study of heat changes that accompany chemical reactions and phase changes |
| universe | System + surroundings |
Endothermic - a chemical reaction or process in which the net exchange of energy is positive; energy is absorbed from the surroundings
Exothermic - a chemical reaction or process in which more energy is released than is required to break the bonds of the reactants; energy is released to the surroundings
Heat of solidification - The amount of heat required to freeze one mole of a liquid substance; equal in value to the heat of fusion but with a negative sign
Heat of condensation - The amount of heat required to condense one mole of a gaseous substance; equal in value to the heat of vaporization but with a negative sign
Standard state - the state of matter in which a substance exists at 25*C and 1 atm
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