THERMOCHEMISTRY

• Thermochemistry

  • Describe the energy exchanges during chemical reaction.
  • Focuses on the energy exchange between a system and its surrounding in the form of heat.
  • Study of heat and energy related to various physical transformation and chemical reaction.
• Scientists have classified everything that exists in the universe into two broad categories, matter and energy.
• Energy maybe transferred into two ways :

  • To cause motion of an object against a force (work).
  • To cause a change in temperature (heat).
• Changes in matter usually accompanied by absorption or evolution of energy.
• The energy change observed is usually a consequence of breaking or formation of bonds.
• A reaction is endothermic if heat is absorbed.
• A reaction is exothermic if heat is evolved or released.
• First Law of Thermodynamics states that "energy cannot be created nor destroyed".
• Thermes is a latin word which means heat.
• Dynamo is a latin word which mean power.
• The first law of thermodynamics is also known as the Law of Conservation of Energy. 
• Energy may be transform from one form to another and that energy lost by the system must be gained by the surroundings, and vice versa.
• Internal energy is the energy contained within a system.
• Internal energy is the sum of the potential and kinetic energy of all components of the system.
• The change in internal energy (∆E), if the transformation is carried out by exchange of heat and performance of work between a system and its surrounding.
• +∆E indicates the net gain of energy by system.
• -∆E indicates the net loss of energy by system.
• The sign of ∆E depends on the magnitude of q and w.
• The symbol of enthalpy change is ∆H
• It is the heat accompanying a chemical reaction.

  Enthalpy Change
• It is also known as heat of reaction.

  Enthalpy Change
• Enthalpy came from the word "Enthalpein", which means to warm.
• The sign of ∆H indicates the direction of heat transfer.
• +∆H means that the reaction is endothermic.
• -∆H means that the reaction is exothermic.
• A balance chemical equation indicating the states of the reactants and the products as well as the value of ∆H found on the right side.

  Thermochemical Equation
• The magnitude of ∆H is proportional to the amount of reactant consumed in the process.
• The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to the ∆H for the reverse reaction.
• The enthalpy change for a reaction depends on the states of the reactants and products. It is a state function and does not depend on the path.