Frequently Asked Question

Energy changes are fundamental to both physical and chemical processes. Here's a breakdown:
Physical Processes:
Phase Changes: Energy is absorbed (endothermic) to break intermolecular forces during melting, vaporization, or sublimation. Conversely, energy is released (exothermic) during freezing, condensation, or deposition.
Dissolving: The process of dissolving can be either endothermic or exothermic, depending on the solute and solvent.
Chemical Processes:
Chemical Reactions: Chemical reactions involve the breaking and forming of chemical bonds. If more energy is released (exothermic) during bond formation than is absorbed (endothermic) during bond breaking, the reaction releases heat. Conversely, if more energy is absorbed than released, the reaction requires heat (endothermic).
Key Concepts:
Enthalpy (H): A measure of the total energy content of a system. Changes in enthalpy (ΔH) are often used to describe energy changes in processes.
Exothermic Reactions: Release heat to the surroundings (ΔH is negative).
Endothermic Reactions: Absorb heat from the surroundings (ΔH is positive).