introduction
Thermodynamics tries to understand and analyze the changes and internal energies in matter.
Heat and work are two equal ways to change the energy of the system. All the energy of an isolated system is constant. The enthalpy change involved once is equal to the heat emitted or absorbed during it at constant pressure.
The system is and the environment is part of what we deal with all the time. The environment and the surroundings together make up the universe.
Work and Heat
Systems and Surroundings
- Closed system – a constant amount of substances remains, but energy exchange occurs between it and the environment.
- Open system – exchange of energy and matter with the environment.
- Isolated system – no exchange of energy and intelligence material takes place in the environment.
Expansion Work
When we look at an area element of size A that is near the flow at pressure P
Heat – The Measurement of Heat
- joule (J)– heat has the unit
- 1 joule=4.2 calorie
Internal Energy
The First Law
The first law of thermodynamics states that the internal energy (U) of a system remains constant, unless it changes as a result of work (W) or heat energy entering or leaving the system.
State Functions A Molecular Interlude
Enthalpy
Heat Transfers at Constant Pressure
At constant pressure, the heat of the reaction equals the system’s enthalpy change (ΔH).
Heat Capacities at Constant Volume and Constant Pressure
The Molecule Origin of the Heat Capacities of Gases
The Enthalpy of Physical Change Heating Curves- The Shape of a Heating Curve?
Thermochemistry
Reaction Enthalpy
The Relation Between AH and AU
Standard Reaction Enthalpies
Combining Reaction Enthalpies:
Hess’s law