PHY1039 Properties of Matter Equation-of-State for an Ideal Gas 13 February, 2012 Lecture 3

ABC Zeroth Law of Thermodynamics If T A = T C and if T B = T C, what can we say about the relation between T A and T B ?

x y z L Ideal Gas Molecules in a Box V = L 3 = volume of box (container) N = number of molecules in the box volume

Wall incident Single Molecule’s Collision with a Wall p p’p’ x m m x After the collision, the momentum transfer to the wall is For the particular case shown here, there is only momentum transfer in the x direction.

x What is the Time between Collisions? A L A = L 2

y z x Kinetic Energy, KE, of Gas Molecule

y z x Significance of the Degrees of Freedom y z x y z x Only one d.o.f. active On average, each d.o.f. contributes ½ kT in thermal energy. For N molecules: For one particular molecule:

Reports on Progress in Physics, vol. 68 (2005) pp. 1043–1094 R = N A k Ideal Gas “Constant”

A constant-volume gas thermometer Why are dilute gases used in this experiment?