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