Chemistry Thermodynamics Lecture 1
Thermodynamics describes the macroscopic state of a (microscopically) complex system through a small number of macroscopic variables (eg Pressure, temperature), the so-called state variables and through the so called thermodynamic potentials
Thermodynamics summarizes the properties of energy and its transformation from one form to another
SYSTEM: what we are interested in (i.e. a block of iron, a beaker of water)
SURROUNDINGS: The remainder of the universe outside the system
OPEN: matter and energy can be exchanged between system and surroundings
CLOSED: ONLY energy can be exchanged
ISOLATED(ADIABATIC): neither matter or energy can be exchanged
The properties of a system depend on the prevailing conditions
Extensive properties: Depending on the quantity of matter in the system (i.e. mass, volume)
Intensive properties: Independent of the amount of matter present (i.e. temperature, density)
State and Path functions
The internal energy (U), Enthalpy (H) & Entropy (S) are STATE functions
Heat(q) and work (w) are path functions
A state function is one whose value depends only on the state of the substance under consideration, it has the same value for a given state no matter how that state came about
A path function depends on the path which the system taks in going between two states
Thermodynamics Fundamentals
0th Law of thermodynamics: all parts of the system within a thermodynamic equilibrium have the same temperature
1st Law: Conservation of energy. The inner energy U of a system can only be changed by heat supply to/ extraction from or work done on/ performed by the system (energy cannot be created or destroyed, but only transformed)
2nd Law: Direction of state changes. Reversible processes have zero-change in entropy. State changes will follow the direction of maximum entropy
3rd Law: Approaching zero temperature (T-0), the entropy becomes constant (set to 0). That is the absolute zero temperature (T=0) cannot be reached
0th Law: if two bodies/ systems having different temperature are brought in contact then the warmer body will get "colder" and the colder body will get warmer until an equilibrium temperature has been reached
Temperature
The thermodynamic temperature (T) is measured in Kelvins (K)
The triple point of water is the point at which the solid, liquid and gaseous state of a system is in equilibrium
0 degrees celsius = -273.15 degrees kelvin
Thermal expansion
The volume of gas increases when heated at constant pressure Charles's Law
When a gas is heated, the gas molecules move faster and hit the wall of the container violently
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