Thermodynamics Flashcards
What is thermodynamics?
Thermodynamics describes the macroscopic state of a (microscopically) complex system through a small number of macroscopic variables (e.g. pressure, temperature), state-variables, and through thermodynamic potentials.
In summary, what is thermodynamics?
Thermodynamics summarises the properties of energy and its transformation from one form to another (deals with the relations between heat and other forms of energy)
Can matter and energy be destroyed?
No, A from of matter is only converted to another form of matter A form of energy is converted to another form of energy
Universe is made of two main components, what are they?
System and Surroundings
What is a System?
What we are interested in (i.e. a block of iron, a beaker of water, an engine, a human body, etc.)
What are the Surroundings?
The remainder of the Universe outside the system (where we stand to make observations about the system and infer its properties)
What is an open system?
where matter and energy can be exchanged between system and surroundings (i.e. an open flask)
What is a closed (diathermic) system?
Only energy can be exchanged (i.e. a sealed bottle)
What is an isolated system?
neither matter or energy can be exchanged (i.e. a stoppered vacuum flask)
The properties of a system depend on what?
the prevailing conditions : extensive and intensive properties
What are extensive properties?
Depending on the quantity of matter in the system (i.e. mass, volume, etc. – 2 Kg of iron occupy twice the volume of 1 Kg of iron)
What are intensive properties?
Independent of the amount of matter present (i.e. temperature, density, etc. - The density of iron is 8.9 Kg.cm3 regardless of whether we have a 1 Kg block or a 2 Kg block)
What is a state function?
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.
What are the three reactions that are state functions?
Internal Energy (U), Enthalpy, H and Entropy, S
What is a path function?
A path function depends on the path which the system takes in going between two states.
What are the two state functions?
heat (q) and work (w)
What is the 0th Law of Thermodynamics?
All parts of system within a thermodynamic equilibrium have the same temperature
What is the 1st Law of Thermodynamics?
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. (in other words: energy can not be created or destroyed, but only transformed)
What is the 2nd Law of Thermodynamics?
Direction of state-changes. Reversible processes have zero-change in entropy S. Irreversible (spontaneous) processes have a positive change in entropy. In other words: state-changes will follow the direction of maximum entropy(-change).
What is the 3rd Law of Thermodynamics (Nernst Theorem):
Approaching zero-temperature (T → 0) , the entropy becomes constant (set to 0). That is, the absolute zero-temperature (T = 0) cannot be reached.
What is the basis of all thermometers?
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 unti an equilibrium temperature has been reached.
What is the (thermodynamic) temperature T is measured in?
Kelvin
How did Lord Kelvin (W. Thomson, 1824-1907) define the temperature scale?
Defined the temperature-scale by the triple-point of water.
What is the triple-point of water?
The triple-point is the point at which the solid, liquid and gaseous state of a system is in equilibrium, at a particular temp and pressure.




