Chemistry: Energy and Chemical Reactions Quiz

Energy and Thermodynamics

• Energy is the ability to do work and is essential for life and modern society.
• Energy is used by every living organism to perform different sustaining functions.
• In chemistry, energy comes from chemical reactions, which obey the law of conservation of mass and the law of conservation of energy.

The First Law of Thermodynamics

• The energy relationships and changes involved in chemical reactions are as important as mass relationships when studying matter.
• Most chemical reactions occur with the absorption or release of energy in the form of heat.
• Heat is the transfer of thermal energy between substances or matter at different temperatures.

Thermal Energy and Temperature

• Temperature is distinct from heat; it is defined as the manifestation of thermal energy.
• Thermal energy is the energy involved in the random motions of atoms and molecules.

Thermochemistry

• Thermochemistry is the study of energy changes in chemical reactions, typically in Joules (J), the SI unit of energy.
• The field involves quantities of heat and work.

Systems in Chemical Reactions

• The system is the part of the universe that is studied, and the rest of the universe is considered the surroundings.
• There are three types of systems: open systems, closed systems, and isolated systems.

Types of Energy Transfers

• Exothermic processes release energy to the surroundings, while endothermic processes absorb energy from the surroundings.

The First Law of Thermodynamics (continued)

• The first law of thermodynamics states that energy cannot be created nor destroyed, only converted from one form to another.
• The exact energy (internal energy) of a system cannot be determined, but changes in energy states can be determined.

Internal Energy

• The internal energy of a system is only concerned with the initial and final states, and it is a state function.
• The internal energy has two components: potential energy and kinetic energy.
• Potential energy is determined by the attractive and repulsive interactions of electrons and nuclei, as well as intermolecular interactions.
• Kinetic energy is described by the random molecular motions and electron movement within molecules.