General Chemistry 2: Thermodynamics and Chemical Thermodynamics

Thermodynamics and Energy Transfer

• Thermodynamics is the scientific study of the interaction of heat and other types of energy.
• Heat energy flows from higher temperature to lower temperature.
• Work done by a system is defined as the quantity of energy exchanged between a system and its surroundings.

Internal Energy

• Internal energy refers to all the energy within a given system, including kinetic energy of molecules and energy stored in chemical bonds.
• The internal energy of a system may change when:
  • Heat passes into or out of the system.
  • Work is done on or by the system.
  • Matter enters or leaves the system.
• Work done BY System is negative, while work done ON System is positive.

Thermodynamic System and Surrounding

• A system is the part of the universe under study where observations are made.
• The surrounding and universe interact with each other, exchanging energy and matter.
• There are three types of systems:
  • Open System: allows exchange of energy and matter.
  • Closed System: allows only energy exchange, but not matter.
  • Isolated System: neither energy nor matter can be exchanged.

Energy Transfer

• Energy transfer occurs in chemical reactions due to absorption or release of energy when chemical bonds are broken or formed.
• The Law of Conservation of Energy states that the total energy of a system must remain unchanged.
• Energy transfer can be classified as:
  • Exothermic Reaction: releases heat and light into surroundings (e.g., combustion reactions).
  • Endothermic Reaction: absorbs heat and/or light from surroundings (e.g., decomposition reactions).

Enthalpy

• Enthalpy is the measurement of energy in a thermodynamic system.
• Enthalpy is the total content of heat of a system, equivalent to the system's internal energy plus the product of volume and pressure.
• The flow of heat (q) at constant pressure in a process equals the change in enthalpy.

Laws of Thermodynamics

• 1st Law of Thermodynamics (Law of Conservation of Energy): energy can neither be created nor destroyed, but it can be changed from one form to another.
• The law can be represented mathematically as: ΔU = ΔQ + W
• Where ΔQ is the heat given or lost, ΔU is the change in internal energy, and W is the work done.