 # Thermochemistry

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More Lessons for High School Chemistry
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A series of free High School Chemistry Video Lessons.

In this lesson, we will learn

• Spontaneous Processes
• Heat of Formation
• Gibbs Free Energy
• Heat of Fusion - Heat of Vaporization
Spontaneous Processes
Spontaneous processes are reactions which proceed without requiring an input of energy because the products are at a lower, more stable energy state than the reactants. Spontaneous processes often require activation energy, but do not require a prolonged input of energy.
Understanding what makes a reaction spontaneous.
This video discriminates between spontaneous (or thermodynamically favored) processes and those that are not spontaneous. A spontaneous process requires no external energy source. If the enthalpy change in a reaction is negative and the entropy is positive a spontaneous process will occur.
Heat of Formation
Heat of formation is the change in enthalpy when one mole of a compound is formed at 25 degrees Celsius and 1 atm from its elements. Heat of formation has been measured in labs and recorded so that we can look it up when we need it.
How to use heat of formation in thermochemical problems.
Standard heat of formation or standard enthalpy change of formation.

Gibbs Free Energy
Gibbs Free Energy is a concept invented to create a thermodynamic relationship between enthalpy and entropy. It is most frequently used with the equation Gibbs free energy = enthalpy - (entropy)(temperature).
Understanding Gibbs Free Energy.
Gibbs Free Energy and Spontaneity Heat of Fusion - Heat of Vaporization
Heat of fusion is the energy needed for one gram of a solid to melt without any change in temperature. Heat of vaporization is the energy needed for one gram of a liquid to vaporize (boil) without a change in pressure. These energies are needed to break apart the intermolecular forces holding the solid or liquid together as it enters a less dense state of matter.
The heat involved in reactions which involve fusion or vaporization.
This video explains the concept of latent heats of fusion and vaporization and work out some problems involving heat of fusion and heat of vaporization of water. Specific Heat, Heat of Fusion and Vaporization
Specific heat and phase changes: Calculating how much heat is needed to convert 200g of ice at -10C to 110 degree steam.

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