(
课件网) Chapter 10 Energy Changes in Chemical Reactions Thermochemistry 10 10.1 Energy and Energy Changes 10.2 Introduction to Thermodynamics States and State Functions The First Law of Thermodynamics Work and Heat 10.3 Enthalpy Reactions Carried Out at Constant Volume or at Constant Pressure Enthalpy and Enthalpy Changes Thermochemical Equations 10.4 Calorimetry Specific Heat and Heat Capacity Constant-Pressure Calorimetry Constant-Volume Calorimetry 10.5 Hess’s Law 10.6 Standard Enthalpies of Formation 10.7 Bond Enthalpy and the Stability of Covalent Molecules 10.8 Lattice Energy and the Stability of Ionic Compounds The Born-Haber Cycle Comparison of Ionic and Covalent Compounds Energy and Energy Changes The system is a part of the universe that is of specific interest. The surroundings constitute the rest of the universe outside the system. The system is usually defined as the substances involved in chemical and physical changes. System Surroundings Universe = System + Surroundings 10.1 Energy and Energy Changes Thermochemistry is the study of heat (the transfer of thermal energy) in chemical reactions. Heat is the transfer of thermal energy. Heat is either absorbed or released during a process. Surroundings heat Energy and Energy Changes An exothermic process occurs when heat is transferred from the system to the surroundings. “Feels hot!” Surroundings Universe = System + Surroundings heat System 2H2(g) + O2(g) 2H2O(l) + energy Energy and Energy Changes An endothermic process occurs when heat is transferred from the surroundings to the system. “Feels cold” energy + 2HgO(s) 2Hg(l) + O2(g) Surroundings Universe = System + Surroundings heat System Introduction to Thermodynamics Thermodynamics is the study of the interconversion of heat and other kinds of energy. In thermodynamics, there are three types of systems: An open system can exchange mass and energy with the surroundings. A closed system allows the transfer of energy but not mass. An isolated system does not exchange either mass or energy with its surroundings. 10.2 open mass & energy Exchange: closed energy isolated nothing Internal energy Internal energy, also called thermodynamic energy the energy associated with the random, disordered motion of molecules or particles. It is separated in scale from the macroscopic ordered energy. Its absolute value is unknown. Its symbol and unit are U and joule respectively. Internal Energy Internal energy: 2 components Kinetic energy - molecular motion Potential energy - attractive/repulsive interactions Internal Energy We cannot calculate the exact value of internal energy with any certainty We can calculate the changes in energy of the system experimentally U = U(products) - U(reactants) Introduction to Thermodynamics State functions are properties that are determined by the state of the system, regardless of how that condition was achieved. The magnitude of change depends only on the i ... ...
