CHEM1 - Kinetic Molecular Theory (KMT)

sublimation

conversion of a solid directly into a gas

condensation

opposite of vaporization

freezing point

temperature at which solid and liquid forms a substance exist in equilibrium

phase changes

conversion of a substance from one of the three physical states of matter to another

vaporization

change of state from liquid to gas

equilibrium vapor pressure

pressure exerted by a constant number of gas molecules above a liquid or a solid

volatile

description of a liquid the evaporates easily

deposition

transformation of a gas directly into a solid

melting

phases change from solid to liquid

freezing/solidification (graph)

• horizontal line

• ←

• liquid to solid

melting (graph)

• horizontal line

• →

• solid to liquid

evaporation/vaporization (graph)

• horizontal line

• →

• liquid to gas

sublimation (graph)

• horizontal line

• →

• solid to gas

condensation (graph)

• horizontal line

• ←

• gas to liquid

deposition (graph)

• horizontal line

• ←

• gas to solid

solid, liquid, gas phases (graph)

diagonal lines

indicates changes in POTENTIAL ENERGY

melting, freezing, condensing, vaporization/evaporation (horizontal lines)

indicates changes in KINETIC ENERGY

solid, liquid, gas (diagonal lines)

correct axis for energy (graph)

x-axis

area for heat of fusion (graph)

same horizontal line where freezing/melting takes place

area for heat of vaporization (graph)

same horizontal line where vaporization/condensation takes place

1 atm = ? torr

760 torr

1 atm = ? psi

14.7 psi

1 atm = ? mm Hg

760 mm Hg

1 atm = ? in Hg

29.92 in Hg

1 atm = ? kPa

101.3 kPa

1 atm = ? Pa

101300 Pa

All collisions between particles in a gas are described as being perfectly ___?___.

elastic (energy is distributed/energy is transferred not lost)

Atmospheric Pressure results from the collisions of air molecules with objects. As you increase your altitude, atmospheric pressure ____?____.

decreases

The device used to measure atmospheric pressure is called a ____?____. The SI unit for pressure is called ___?___.

barometer, Pascal (Pa)

Weather in a given area is based off of barometric pressure: If pressure is rising, this weather should be ______.

clear

Weather in a given area is based off of barometric pressure: If pressure is falling, this weather should be ______.

stormy

What are the conditions described for STP (Standard Temperature and Pressure)?

T→ 0°C/273°K/32°F

P→ 1 atm (or any of the conversions)

Kinetic Theory:

• tiny particles in all forms of matter are in constant motion

• explains properties of solids, liquids, and gases

Solids:

• closely packed

• intermolecular forces are VERY effective

• vibrational movements

• Crystalline→ definite MP, KE of particles overcome attractive forces of solid, 3D arrangement of particles of crystals (unit cell - smallest portion of a crystal that shows the 3D structure)

• Amorphous→ no definite MP

• supercooled liquids

• Highest density (10% more than liquid)

• High incompressibility

• Low diffusion rate: very slow

Gas:

• no definite shape/volume

• small particles, hard spheres, insignificant volume (very far apart)

• move rapidly in constant, random motion

• All collisions are perfectly elastic (energy is transferred, NOT LOST)

• no forces of attraction/replusion b/w particles

Gas Pressure

is the result of simultaneous collisions of billions of gas particles w/ an obj.

Vacuum

when no gas particles are present

Atmospheric Pressure

• Results from the collisions of air molecules w/ objs.

• decreases as you climb a mountain b/c the air layer around Earth thin at high elevations

Barometer

• measure atmospheric pressure

• SI unit of pressure = pasal (Pa)

• Atm pressure at sea level = STP (0°C)

Millimeters of Mercury (mmHg)

Pressure of that supports 1mm of Hg in a barometer

Torricelli (torr)

1 torr = 1mmHg

Atmosphere (atm)

Average atmospheric pressure at sea level at 0°C

Pascal (Pa)

SI unit for pressure, 1 Pa = 1 N/m²

Liquids

• Fluid: flows, hence takes shape of its container

• High density (1000x greater than gas, 10% less than solids)

• Relatively incompressible (volume only decreases by 4% under 1000 atm of pressure)

• Can diffuse: slower in liquids than gas due to slower motion & attractive forces

Atmospheric Pressure and Boiling Point: Sea level

• atm pressure at surface of water at 70°C is greater than its vapor pressure; bubbles of vapor CANNOT form in water and does not boil

• at BP vapor pressure = atm pressure; bubbles of vapor form in water and boils (100°C)

Atmospheric Pressure and Boiling Point: Mt. Everest

• at hight altitudes, atm pressure is lower that its sea level

• thus water boils at a lower temp. (70°C)

Vapor Pressure:

particles collide with the walls of the sealed container.

• Dynamic Equilibrium

Evaporation (vaporization):

conversion of a liquid to a gas or vapor below its boiling point.

Boiling Point:

temp. at which the v.p. of the liquid is just equal to the external pressure.