Chemical Reactions and Energy Transformation

Energy Transformations in Chemical Reactions

• Two types of energy: kinetic (energy of motion) & potential (stored energy in position/configuration).

• Energy transforms between types; total energy remains constant.

Kinetic and Potential Energy

• Kinetic energy includes sound, thermal energy, electricity, electromagnetic radiation (light).

• Potential energy is stored in chemical bonds; influenced by electron position relative to atomic nuclei.

Chemical Reactions and Energy

• In chemical reactions, potential energy converts to kinetic energy (thermal/light).

• Enthalpy (H): total energy = potential energy in bonds + kinetic energy effects.

• Change in enthalpy (∆H) indicates heat release/absorption:

  • Exothermic: heat released (∆H < 0).

  • Endothermic: heat absorbed (∆H > 0).

Entropy and Spontaneity

• Entropy (S): measure of disorder. Higher disorder means higher entropy (∆S > 0).

• Second law of thermodynamics: total entropy always increases in a closed system.

• Gibbs free energy (G): determines spontaneity of reactions.

  • ∆G = ∆H - T∆S (T in Kelvin)

  • Exergonic: spontaneous (∆G < 0).

  • Endergonic: nonspontaneous (∆G > 0).

  • Equilibrium: ∆G = 0.

Factors Affecting Reaction Rates

• Reaction rates depend on temperature (higher = faster) and concentration (higher = more collisions).

• Reactions require bonds to break/form through collisions at specific orientations.

• Higher temperature/concentration increases reaction rates.

Summary of Experimental Findings

• Hypothesis: reaction rates increase with more collisions (higher temperature/concentration).

• Results showed that reaction rates are higher with increased temperature and concentration, confirming the hypothesis.