Key Concepts in Thermodynamics and Thermochemistry

Posted on Apr 3, 2025 in Chemistry

• Calorie: A unit of power based on the specific heat of water, used to express the energy value of food.
• State Function: A macroscopic physical quantity that characterizes the state of a system in equilibrium.
• Internal Energy: The total change in internal energy equals the sum of the energy supplied to the system as heat and work.
• Heat of Reaction: The heat absorbed or released during a chemical reaction at constant pressure.
• Heat: The amount of energy a thermodynamic system can exchange with its environment.
• Heat of Formation: The heat required to form one mole of a substance from its constituent elements at constant pressure.
• Isobaric Process: A thermodynamic process that occurs at constant pressure, where heat transfer is related to other variables.
• Exothermic Reaction: A chemical reaction that releases heat (negative change in enthalpy).
• Endothermic Reaction: A chemical reaction that absorbs heat.
• Hess’s Law: The heat change in a reaction is the same regardless of the number of stages. Used to predict enthalpy change.
• Law of Conservation of Mass (Lavoisier’s Law): In any chemical reaction, mass is conserved; the total mass of reactants equals the total mass of products.
• Law of Laplace: Defines the pressure ratio necessary to obtain a neutral balance between two spaces.
• Thermodynamics: A branch of physics studying the effects of changes in temperature, pressure, and volume of systems at a macroscopic level. It explains the exchange of mass and heat between thermal systems.
• Specific Heat: The amount of heat required to raise the temperature of a unit mass of a substance by one unit.
• State Properties: Properties that depend only on the initial and final states of a system.
• Energy: The ability to do work, transferred from one form to another to accumulate or expend.
• Internal Energy: The sum of the individual energies of all particles in a system.
• Heat: The heat flow at constant pressure is called the enthalpy change.
• Adiabatic Process: A change within a system without heat exchange with the external environment.
• Thermochemistry: An area of thermodynamics that studies the thermal changes in chemical processes.
• Spontaneity: A process that occurs naturally in a particular direction.
• Reactivity: The ability of reactants to transform into products.
• Entropy: A thermodynamic function measuring the disorder of a system; higher disorder means more entropy.
• Gibbs Free Energy: Indicates the energy available to do work, determining equilibrium and spontaneity for a chemical reaction.

Chemical Equilibrium Concepts

• Chemical Equilibrium: If the equilibrium constant is greater than 1, the equilibrium favors product formation. If less than 1, it favors reactant formation.
• Homogeneous Equilibrium: All reaction components are in the same phase.
• Heterogeneous Equilibrium: Reaction components are in different phases.
• Le Chatelier’s Principle: If a chemical system in equilibrium experiences a change in concentration, temperature, volume, or partial pressure, the equilibrium shifts to counteract the change. This principle is equivalent to the principle of energy conservation.