Topic 10: Thermodynamics Flashcards
Thermodynamics
Processes which cause energy changes as a result of heat flow to/from a system and/or work done by/on a system.
Ideal gas
The molecules obey Newton’s laws; The intermolecular forces are negligible; The molecules are spherical with negligible volume; The motion of the molecules is random; The collisions are perfectly elastic; The time taken for a collision is negligible.
Absolute zero of temperature
The lowest temperature possible. -273.16°C or zero kelvin (0K). The temperature at which the volume, pressure and kinetic energy of an ideal gas are zero.
Internal energy
The energy contained in an object due to the random KE and PE of the molecules.
First law of thermodynamics
The heat supplied to a mass of gas is equal to the increase in its internal energy plus the work done by the gas (expansion is positive work).
Thermal energy
The non-mechanical transfer of energy between a system and its surroundings. Energy is only ‘heat’ if it is transferred.
System and surroundings
The fixed mass of gas which is under consideration can be called the ‘system’, the place to/from which heat flows is the ‘surroundings’.
Isochoric change
A change in a gas where the volume remains constant.
Isobaric change
A change in a gas where the pressure remains constant.
Isothermal change
A change in a gas where the temperature remains constant.
Adiabatic change
A change in a gas where no energy enters or leaves the system.
Entropy
A measure of disorder of a system. It is measured in JK-1.
Second law of thermodynamics
No continually working heat engine can take heat from a source and convert it completely into work.
OR: Thermal energy cannot spontaneously transfer from a region of low temperature to a region of high temperature.
OR: Although local entropy may decrease, the direction of a process is such as to increase the total entropy of the system and surroundings.
