Energy and Thermochemistry Overview

Energy and Thermochemistry

• Energy is the ability to do work or produce heat.
• Kinetic energy is the energy of motion.
• The equation for calculating heat (q) is q = cxmxΔT (where c is specific heat, m is mass, and ΔT is change in temperature).

Conservation of Energy

• The law of conservation of energy states that energy is neither created nor destroyed, but can be converted from one form to another. This is also known as the first law of thermodynamics.

Thermochemistry

• Thermochemistry studies heat changes.
• The enthalpy of reaction (ΔH_rxn) is calculated as: ΔH_rxn = H_products - H_reactants (where H represents enthalpy).

Thermochemical Equations

• A thermochemical equation includes:
  • The physical states of reactants and products (e.g., solid, liquid, gas).
  • A balanced chemical equation.
  • The change in enthalpy (ΔH).

Standard Enthalpy of Formation

• The standard enthalpy of formation of elements in their standard states is always 0.0 kJ.

Entropy

• Entropy (S) is a measure of the disorder or randomness of particles in a system.
• Entropy decreases when the number of particles in a system decreases.

Second Law of Thermodynamics

• The second law of thermodynamics states that spontaneous processes always proceed in a way that increases the entropy of the universe.

Collision Theory

• Collision theory explains reaction rates.
  • Reactants must collide in the correct orientation.
  • Collisions must have sufficient energy to form an activated complex.

Exothermic Reactions

• Exothermic reactions release energy, resulting in products at a lower energy level.