Tiêu đề CHEM CH 06.pdf ✅

Thermodynamics 2 | P a g e Heterogeneous system: A mixture is said to be heterogeneous when it consists of two or more phases and the composition is not uniform. For example: A mixture of insoluble solid in water. ’ The state of the system: The state of a thermodynamic system means its macroscopic or bulk properties which can be described by state variables: Pressure (P), volume (V), temperature (T) and amount (n) etc. They are also known as state functions. Isothermal process: When the operation is carried out at constant temperature, the process is said to be isothermal. For isothermal process, dT = 0 Where dT is the change in temperature. Adiabatic process: It is a process in which no transfer of heat between system and surroundings, takes place. Isobaric process: When the process is carried out at constant pressure, it is said to be isobaric. i.e. dP = 0 Isochoric process: A process when carried out at constant volume, it is known as isochoric in nature. Cyclic process: If a system undergoes a series of changes and finally returns to its initial state, it is said to be cyclic process. Reversible Process: When in a process, a change is brought in such a way that the process could, at any moment, be reversed by an infinitesimal change. The change r is called reversible. • Internal Energy It is the sum of all the forms of energies that a system can possess. In thermodynamics, it is denoted by AM which may change, when — Heat passes into or out of the system — Work is done on or by the system — Matter enters or leaves the system. Change in Internal Energy by Doing Work Let us bring the change in the internal energy by doing work. Let the initial state of the system is state A and Temp. TA Internal energy = uA On doing’some mechanical work the new state is called state B and the temp. TB. It is found to be TB > TA uB is the internal energy after change. ∴ Δu = uB – uA Change in Internal Energy by Transfer of Heat Internal energy of a system can be changed by the transfer of heat from the surroundings to the system without doing work. Δu = q Where q is the heat absorbed by the system. It can be measured in terms of temperature difference. q is +ve when heat is transferred from the surroundings to the system. q is -ve when heat is transferred from system to surroundings. When change of state is done both by doing work and transfer of heat. Δu = q + w First law of thermodynamics (Law of Conservation of Energy). It states that, energy can neither be created nor be destroyed. The energy of an isolated system is constant. Δu = q + w.