The division of electron shells or energy levels defined by a particular value of the azimuthal
quantum number; e.g., s, p, d, and f subshells. Composed of orbitals. Also called sublevels. See
Orbital.
Surroundings
All matter and energy in the universe not included in the particular system under consideration.
System
The matter and energy under consideration.
Temperature
A measure of the average energy of motion of the particles in a system.
Third law of thermodynamics
The law stating that the entropy of a perfect crystal at absolute zero is zero.
Titrant
A solution of known concentration that is slowly added to a solution containing an unknown
amount of a second species to determine its concentration.
Titration, acid-base
A method used to determine the concentration of an unknown solution.
Titration curve
A plot of the pH of a solution versus the volume of acid or base added in an acid-base titration.
Torr
A pressure unit equal to 1 mm Hg. 760 torr = 1 atm.