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Chapter 9

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

Department
Physics
Course Code
PHYS 22000
Professor
Moffett Thomas
Chapter
9

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Physics Chapte r 9 Notes
9.1 Structure of Matte r:
â€¢ Particles move ra ndomly in a ll directions a nd compos e things such a s liquids
â€¢ 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
â€¢ Atoms a re the smallest objects tha t reta in che mica l prope rties of a pa rticula r e le me nt
â€¢ Compos e d of protons , ne utrons, a nd e le ctrons
â€¢ A mole cule is a certain combina tion of atoms tha t bond together in a particula r a rrange me nt
â€¢ A mole cule ma y conta in two, thre e, or ma ny a toms
â€¢ Gasses, Liquids, and Solids
â€¢ 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)
â€¢ 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
â€¢ 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
that
â€¢ Ideal Gas Law
â€¢ 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
â€¢ We a s s ume the motions of the particles obe y Newtonâ€™s 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
â€¢ 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 â€™s la ws
â€¢ Ide a l me a ns s implified
9.2 Pres sure, Dens ity, and the Ma s s of Pa rticle s:
â€¢ Pressure:
â€¢ 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 âŠ¥ 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 =FâŠ¥/A
â€¢ SI unit is the pa s ca l PA whe re 1 Pa = 1N/mÂ²
â€¢ Measuring Pressure:
â€¢ The atmos phe ric pressure a t s e a leve l is 10^5 N/mÂ²
â€¢ 1 a tm = 1.0 x 10^5 P a
â€¢ 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
â€¢ Pgauge = P - Patm, whe re P a tm= 1.0 a tm = 1.0 x 10^5 N/mÂ²
â€¢ Density
â€¢ Measure s the ma s s of one cubic me ter of a s ubs ta nce
â€¢ 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
â€¢ p = m/V
â€¢ Unit is kg/m^3
â€¢ Mass and Particle Size
â€¢ Avoga droâ€™s numbe r and the mole : Avoga droâ€™s numbe r NA = 6.02 x 10^23 particles and is
calle d a mole
â€¢ 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
â€¢ 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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