THERMOCHEMISTRY & CHEMICAL THERMODYNAMICS (4th quarter)

• thermodynamics: the branch of physical science that deals with the relations between heat and other forms of energy (such as mechanical, electrical, or chemical energy), and, by extension, of the relationships between all forms of energy.
• heat - defined as the kinetic energy of the molecules of the substance.
• Heat and thermodynamics together form the basics which helped process designers and engineers to optimize their processes and harness the energy associated with chemical reactions economically.
• 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.
• Work is completely governed by external factors such as an external force, pressure, volume, or change in temperature, etc.
• The relationship between the two concepts (heat and work) can be analyzed through the topic of thermodynamics.
• Energy cannot be created or destroyed, but it can be converted or transferred
• Internal energy refers to all the energy within a given system, including the kinetic energy of molecules and the energy stored in all of the chemical bonds between molecules
• With the interactions of heat, work, and internal energy, there are energy transfers and conversions every time a change is made to a system. However, no net energy is created or lost during these transfers.
• 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 or matter enters or leaves the system.
• Thermodynamics defines a system as the part of the universe under study that us the part where observations are made.
• There are three types of system:

  • open system
  • closed system
  • isolated system
• Open System - A system with which mass can enter or leave through its boundaries.
• Closed System - A system whose boundary does not allow any material to pass through it but allows energy transfer across the boundary.
• Isolated System - A system that neither gains nor loses energy and matter from outside sources.
• Law of Conservation of Energy - physical law that states that energy cannot be created or destroyed, only transferred from one form to another.
• Enthalpy: a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.
• Exothermic reaction release heat and light into their surroundings. The energy required to break the bonds in the reactants is less than the energy released when new bonds form in the products.
• endothermic has a negative enthalpy change and is spontaneous. exothermic has a positive enthalpy change and is not spontaneous.
• endothermic reaction absorbs heat and/or light from their surroundings. The energy required to break the bonds in the

  reactants is more than the energy released when new bonds form in the products; in other words, the reaction requires energy to proceed.