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Chapter 9

PHYS 22000 Chapter Notes - Chapter 9: Ideal Gas Law, Pressure Measurement, Ideal Gas

Course Code
PHYS 22000
Moffett Thomas

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Physics Chapte r 9 Notes
9.1 Structure of Matte r:
Particles move ra ndomly in a ll directions a nd compos e things such a s liquids
Particles ne ed e mpty s pace be twee n them so tha t particles of othe r ma teria ls ca n move
between the m
Atoms a re the smallest objects tha t reta in che mica l prope rties of a pa rticula r e le me nt
Compos e d of protons , ne utrons, a nd e le ctrons
A mole cule is a certain combina tion of atoms tha t bond together in a particula r a rrange me nt
A mole cule ma y conta in two, thre e, or ma ny a toms
Gasses, Liquids, and Solids
Ga s e s te nd to occupy wha te ve r volume is availa ble and pa r packed much loos e ly (lots of
empty space)
In orde r for the pa rticle s to form a s ubs ta nce , the y must s ome how be a ttra cte d to e ach othe r
The attra ctive force s in liquids a re s tronger than ga s , a nd s olids a re e ven s tronger tha n
Ideal Gas Law
As s ume the dista nce be twee n the pa rticle is much la rge r tha n the a ctua l pa rticle
We a s s ume the motions of the particles obe y Newtons laws, the refore , the pa rticles move in
stra ight line s at consta nt velocity and only cha nge the ir ve locities during collisions
Ide a l ga s mode l: A model of a s ys te m in which ga s pa rticle s are conside re d point-like a nd
only inte ra ct with e a ch other a nd the walls of the ir conta ine r through collis ions , a nd a lso
as s ume s that the particles a nd the ir inte ractions are a ccurately de s cribing Newtons s la ws
Ide a l me a ns s implified
9.2 Pres sure, Dens ity, and the Ma s s of Pa rticle s:
Pres s ure: A physica l quantity e qua l to the ma gnitude of the pe rpe ndicula r compone nt of the
Force tha t a ha s , liquid, or solid e xerts on a s urfa ce divide d by the contact are a A ove r
which tha t force is e xerted P =F/A
SI unit is the pa s ca l PA whe re 1 Pa = 1N/m²
Measuring Pressure:
The atmos phe ric pressure a t s e a leve l is 10^5 N/m²
1 a tm = 1.0 x 10^5 P a
Ga uge pre ss ure : the diffe re nce betwee n the pre ss ure in s ome conta iner and the
atmos pheric pre s s ure outs ide the conta ine r
Pgauge = P - Patm, whe re P a tm= 1.0 a tm = 1.0 x 10^5 N/m²
Measure s the ma s s of one cubic me ter of a s ubs ta nce
The de nsity p of a s ubs ta nce or of an object e qua ls the ratio of mas s m of a volume V of the
substa nce divide d by tha t volume
p = m/V
Unit is kg/m^3
Mass and Particle Size
Avoga dros numbe r and the mole : Avoga dros numbe r NA = 6.02 x 10^23 particles and is
calle d a mole
The numbe r of particles in a mole is the sa me for all s ubs tance s a nd is the number of
particles whos e tota l mas s e qua ls the a tomic mass of that subs ta nce
The mass of one mole of pa rticles of any s ubs ta nce is ca lle d mola r ma ss
9.3 Qua ntitative Ana lys is of Ide al Ga s La w
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