During an energy exchange, a chemical system absorbs energy from its surroundings. What is the sign of \(\Delta E _ { \text { wh } }\) for this process? Explain.

Internal energy, denoted by the symbol \( U \), is a measure of the total energy stored within a chemical system. It encompasses all forms of energy present, including kinetic energy from the movement of particles and potential energy due to molecular structure and intermolecular forces. In the context of a chemical reaction or physical process, changes in internal energy are symbolized by \( \Delta E \) or \( \Delta U \).

When a system absorbs energy, its internal energy increases, and \( \Delta E \) is positive. Conversely, when a system releases energy to its surroundings, \( \Delta E \) is negative. Understanding this concept is crucial because it lays the foundation for predicting how energy will flow during chemical processes, affecting reaction spontaneity and equilibrium.

Energy absorption in chemistry refers to the process by which a substance takes in energy from its external environment. This can happen in various forms, such as heat, light, or electrical energy. When energy is absorbed, molecular vibrations, rotations, and translations increase, leading to a higher internal energy state.

The magnitude of energy absorbed can vary depending on the nature of the substances involved and the conditions under which the absorption takes place, such as temperature and pressure. In a classroom or homework setting, recognizing energy absorption is vital to understanding endothermic processes, where the absorbed energy is often evidenced by a temperature decrease in the surroundings.

Thermochemistry deals with the study of the energy and heat associated with chemical reactions and physical transformations. It is a branch of thermodynamics that provides insights into the energy exchange processes that occur during a reaction. One key principle in thermochemistry is the conservation of energy: energy can neither be created nor destroyed, only transformed or transferred.

In a thermochemical equation, the enthalpy change (\( \Delta H \)) represents the heat absorbed or released under constant pressure. If \( \Delta H \) is positive, the process is endothermic (heat absorbed); if it is negative, the process is exothermic (heat released). Understanding thermochemistry is critical for predicting reaction behavior and designing processes that harness or mitigate energy changes.