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Atom – smallest piece of an element
Molecule – smallest piece of a compound – two or more atoms chemically bonded
Mole – counting number equal to 6.022 x 10 23
Molar Mass – number of grams of a substance per mole – equal to the atomic mass on the periodic table

 How many moles in 5.5g of hydrogen gas?
 How many molecules in 2.5 moles of oxygen?
 What is the mass of one molecule of helium gas?

 Matter is made of particles in continuous motion
 Particles move in random directions at a variety of speeds
 Particles of gases are on average very far apart from one another

 Molecules of gases interact only when they collide
 Collisions are perfectly elastic (no loss of kinetic energy)

 1atm = 760mmHg = 760torr = 101kPa
 STP – standard temp and pressure (0 ° C and 1 atm)

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Volume is proportional to the temperature –
Charles Law ( V
1
/T
1
= V
2
/T
2
)
Volume is inversely prop to temp – Boyles Law
( P
1
V
1
= P
2
V
2
)
Pressure is prop to temp – Gay-Lussac’s Law
( P
1
/T
1
= P
2
/T
2
)
Combined Gas Law puts them together
( P
1
V
1
/T
1
= P
2
V
2
/T
2
)

 One that follows all kinetic theory
 Volume of a gas also depends on the number of moles
 Ideal Gas Law
PV = nRT R = .0821 L •atm/ mol•K

 Determine the volume of 1.00 mole of a gas at
STP.
 A container of oxygen at STP has a volume of
10.0 L. What is the mass of the gas?

 A helium party balloon has a radius of 18.0cm at 20 ° C and 1.05 atm. How many moles of He are in the balloon and what is the mass of the gas in the balloon?
 An auto tire is filled to a pressure of 200kPa at
10 ° C. After driving 100km, the temp rises to
40 ° C. What is the pressure now?

 The average KE of molecules is directly proportional to the temp
KE = ½ mv 2 = 3/2 kT k – Boltzman’s Constant = 1.38x10
-23 J/K

 What is the average KE of gas molecules at
37 ° C?

 Also called root mean square velocity
 v rms
= 3 kT
M m – mass (in kg) of one molecule of the gas

 What is the rms speed of an oxygen molecule at 20 ° C?