CHE201 Handouts Set 2

Physical Chemistry CHE201 Handouts Virtual University of Pakistan

Lecture 1.

Physical Chemistry:

Physical chemistry is the study of the underlying physical principles that govern the properties and behavior of chemical systems.

Chemical System:

A chemical system can be studied from either a microscopic or a macroscopic viewpoint. The microscopic viewpoint is based on the concept of molecules. The macroscopic viewpoint studies large-scale properties of matter without explicit use of the molecule concept. Lecture 2.

Thermodynamics:

Thermodynamics: (Greek words for “thermo=heat” and “dynamics=power”) is the study of heat, work, energy, and the changes they produce in the states of systems. Thermodynamics studies the relationships between the macroscopic properties of a system A key property in thermodynamics is temperature Thermodynamics is sometimes defined as the study of the relation of temperature to the macroscopic properties of matter Equilibrium Thermodynamics: It deals with systems in equilibrium It is a macroscopic science and is independent of any theories of molecular structure Irreversible Thermodynamics: It deals with non-equilibrium systems and rate processes. Lecture 3.

Thermodynamic Systems:

The macroscopic part of the universe under study in thermodynamics is called the System The parts of the universe that can interact with the system are called the surroundings. Open system is one where transfer of matter between system and surroundings can occur. Closed system is one where no transfer of matter can occur between system and surroundings. Isolated system is one that does not interact in any way with its surroundings. An isolated system is obviously a closed system, but not every closed system is isolated.

Lecture 4.

Equilibrium

Equilibrium thermodynamics deals with systems in equilibrium An isolated system is in equilibrium when its macroscopic properties remain constant with time A non-isolated system is in equilibrium when the following two conditions hold A. The system’s macroscopic properties remain constant with time B. Removal of the system from contact with its surroundings causes no change in the properties of the system If condition (A) holds but (B) does not hold, the system is in a steady state. Mechanical Equilibrium: No unbalanced forces act on or within the system; hence the system undergoes no acceleration, and there is no turbulence within the system. Material Equilibrium: No net chemical reactions are occurring in the system, nor is there any net transfer of matter from one part of the system to another or between the system and its surroundings Thermal Equilibrium between a system and its surroundings, there must be no change in the properties of the system or surroundings when they are separated by a thermally conducting wall. For thermodynamic equilibrium, all three kinds of equilibrium must be present. Lecture 5.

Thermodynamic Properties:

An extensive thermodynamic property is one whose value is equal to the sum of its values for the parts of the system. Thus, if we divide a system into parts, the mass of the system is the sum of the masses of the parts; mass is an extensive property. So is volume. Intensive thermodynamic property is one whose value does not depend on the size of the system, provided the system remains of macroscopic size-recall nanoscopic systems Density and pressure are examples of intensive properties. If each intensive macroscopic property is constant throughout a system, the system is homogeneous. If a system is not homogeneous, it may consist of a number of homogeneous parts. A homogeneous part of a system is called a phase A system composed of two or more phases is heterogeneous Suppose that the value of every thermodynamic property in a certain thermodynamic system equals the value of the corresponding property in a second system. The systems are then said to be in the same thermodynamic state

Lecture 6. Temperature:

Suppose two systems separated by a movable wall are in mechanical equilibrium with each other Because we have mechanical equilibrium, no unbalanced forces act and each system exerts an equal and opposite force on the separating wall.