Topic 8, Gases

Topic 8, Gases
(Key concepts)

KMT (ideal gases)

The particles making up a gas sample … (assumptions)

1.     are in constant, random, straight-line motion

2.    collide resulting in the transfer of energy while the total amount of energy remains the same

3.    have no volume

4.    have no attraction for one another

Real gases, however, are made up of particles that… (deviations)

*have volume (incredibly tiny)

*have forces of attraction (extremely weak)

Hydrogen gas and helium gas behave most like ideal gases because they are small and nonpolar, making their forces of attraction extremely weak.

The conditions of high temperature and low pressure allow gases to behave most like ideal gases because the high temp gives the particles the energy needed to overcome forces of attraction and the low pressure allows the gas particles to spread out reducing the forces of attraction.

Relationships between P, T, V, v, # of particles

Direct: One goes up, the other goes up; one goes down, the other goes down.

TV, Tv, P#, TP

Inverse:  One goes up, the other goes down.

PV  (PVC pipe is the memory tool)

Combined Gas Law

The combined gas law is listed in Table T.  It represents the mathematical relationship among T, P, and V.

P1V1 = P2V2

T1         T2

The temperature must be in the Kelvin scale.  K = oC + 273

Can you figure out what happened to this tanker?

The tanker was steam cleaned one evening and then sealed for the night.  It looked like this in the morning.

Tell Mrs. Coon what you think happened and why.