nature of gases (and liquids and solids). kinetic-molecular theory assumptions size: gases are tiny...

Nature of Gases(and liquids and solids)

Nature of Gases(and liquids and solids)

Kinetic-Molecular Theory Assumptions

Kinetic-Molecular Theory Assumptions

Size: gases are tiny particles separated by empty space; they do not attract or repel each other

Motion: gas particles are in constant, random motion

Energy: collisions between particles are elastic (no energy is lost)

Size: gases are tiny particles separated by empty space; they do not attract or repel each other

Motion: gas particles are in constant, random motion

Energy: collisions between particles are elastic (no energy is lost)

Pressure Units (you don’t have to copy this,

but you do need to recognize which units are for pressure!)

Pressure Units (you don’t have to copy this,

but you do need to recognize which units are for pressure!)

Unit compared w/ 1 atm compared w/ 1 kPa

kilopascal (kPa) 1 atm = 101.3 kPa

millimeters of mercury (mm Hg)

1 atm = 760 mm Hg 1 kPa = 7.501 mm Hg

torr 1 atm = 760 torr 1 kPa = 7.501 torr

pounds per square inch (psi)

1 atm = 14.7 psi 1 kPa = 0.145 psi

atmosphere (atm) 1 kPa = 0.009869 atm

Comparison of Pressure Units

These are conversion factors! STOP & THINK: How many atmospheres do you have if you have 50.65 kilopascals?

Soda Air Pressure

http://www.youtube.com/watch?v=t-Iz414g-ro&feature=related

Energy in GasesEnergy in Gases Temperature (in Kelvin) is the

measure of the amount of energy in a gas sample.

Average kinetic energy is proportional to Kelvin temperature.

All samples at the same temperature have the same average kinetic energy.

Kelvin = °Celsius + 273

Temperature (in Kelvin) is the measure of the amount of energy in a gas sample.

Average kinetic energy is proportional to Kelvin temperature.

All samples at the same temperature have the same average kinetic energy.

Kelvin = °Celsius + 273

sToP & tHinKsToP & tHinK

You have two samples of gas at 22 C, one is hydrogen and one is oxygen. What is the temperature in Kelvin? How do their kinetic energies

compare?

You have two samples of gas at 22 C, one is hydrogen and one is oxygen. What is the temperature in Kelvin? How do their kinetic energies

compare?

http://www.youtube.com/watch?v=UNn_trajMFo

What about liquids? (don’t copy)What about liquids? (don’t copy)

More attractive force between particles than for gases

Particles can flow past each other Relationship between temperature

and kinetic energy still applies!

More attractive force between particles than for gases

Particles can flow past each other Relationship between temperature

and kinetic energy still applies!

What about solids? (don’t copy)What about solids? (don’t copy)

More attractive force between particles than for gases and liquids

Particles vibrate around a point… no flow, fixed locations

Different crystalline and non-crystalline forms depending on the atoms present

Relationship between temperature and kinetic energy still applies!

More attractive force between particles than for gases and liquids

Particles vibrate around a point… no flow, fixed locations

Different crystalline and non-crystalline forms depending on the atoms present

Relationship between temperature and kinetic energy still applies!

Phase ChangesPhase Changes

Require Energy: melting: s --> l vaporization: l --> g sublimation: s --> g

Release Energy: condensation: g --> l deposition: g --> s freezing: l --> s

Require Energy: melting: s --> l vaporization: l --> g sublimation: s --> g

Release Energy: condensation: g --> l deposition: g --> s freezing: l --> s

Phase DiagramsPhase Diagrams show the phase a substance will be at a

specific pressure (P) and temperature (T)

Triple point: P & T at which all three states of matter will be present

show the phase a substance will be at a specific pressure (P) and temperature (T)

Triple point: P & T at which all three states of matter will be present

http://web.visionlearning.com/custom/chemistry/animations/CHE1.1-an-threestates.shtml

Vaporization - how sweat cools your body

Vaporization - how sweat cools your body

Fastest moving particles go from liquid to gas phase

Overall kinetic energy of liquid phase drops, so temperature drops

Energy is required to give particles the velocity to change phase - that energy comes from your body heat.

Fastest moving particles go from liquid to gas phase

Overall kinetic energy of liquid phase drops, so temperature drops

Energy is required to give particles the velocity to change phase - that energy comes from your body heat.^ a close up of your sweaty armpit

DiffusionDiffusion movement from high to low

concentration caused by random collisions in which no

energy is lost rate of diffusion depends on

temperature (amt of KE) and the mass of the particles

movement from high to low concentration caused by random collisions in which no

energy is lost rate of diffusion depends on

temperature (amt of KE) and the mass of the particles

air sprayssalt in beakerdye in beaker…

Dalton’s Law of Partial Pressures

Dalton’s Law of Partial Pressures

At a specific temperature and pressure, the ‘partial’ pressure of one mole of gas is the same regardless of the gas identity.

In a gas mixture, the total pressure equals the sum of the pressure of each gas.

P total = P1 + P2 + P3 + …. Pn

At a specific temperature and pressure, the ‘partial’ pressure of one mole of gas is the same regardless of the gas identity.

In a gas mixture, the total pressure equals the sum of the pressure of each gas.

P total = P1 + P2 + P3 + …. Pn

sToP & tHinKsToP & tHinK You are asked to add chlorine to your

neighbor’s swimming pool and spa while they’re out of town. In which one will the chlorine totally spread out in the liquid faster? Use the assumptions from kinetic molecular

theory to explain! A sample of gas has a total pressure of 5

atm. It contains argon and one unknown gas. The argon contributes 3.5 atm of pressure. What is the pressure of the unknown gas? Can we use this information to figure out the

identity of the gas?!?!

You are asked to add chlorine to your neighbor’s swimming pool and spa while they’re out of town. In which one will the chlorine totally spread out in the liquid faster? Use the assumptions from kinetic molecular

theory to explain! A sample of gas has a total pressure of 5

atm. It contains argon and one unknown gas. The argon contributes 3.5 atm of pressure. What is the pressure of the unknown gas? Can we use this information to figure out the

identity of the gas?!?!