PHASE CHANGES. Kinetic Theory Kinetic = motion Particles in a gas are considered to be hard, small...
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Transcript of PHASE CHANGES. Kinetic Theory Kinetic = motion Particles in a gas are considered to be hard, small...
Kinetic TheoryKinetic Theory
Kinetic = motionKinetic = motion
Particles in a gas are Particles in a gas are considered to be hard, small considered to be hard, small spheres with an spheres with an insignificant volume.insignificant volume.
The motion of particles in a The motion of particles in a gas is rapid, constant, and gas is rapid, constant, and random.random.
All collisions All collisions between particles in between particles in a gas are perfectly a gas are perfectly elastic.elastic.
Particles in a gas Particles in a gas only interact when only interact when they collide.they collide.
Temperature (in Temperature (in kelvins, K) is directly kelvins, K) is directly proportional to the proportional to the average kinetic average kinetic energy of the energy of the particles of a particles of a substance.substance.
Objects expand when Objects expand when heated because of heated because of increased vibrational increased vibrational motion.motion.
Gas pressure is caused by the Gas pressure is caused by the collisions of particles with an object collisions of particles with an object (wall).(wall).
Atmospheric pressure results from the Atmospheric pressure results from the weight of air above an object.weight of air above an object.
Higher altitudes have less atmospheric Higher altitudes have less atmospheric pressure.pressure.
Standard atmospheric pressure is:Standard atmospheric pressure is:
1 atm = 101.3 kPa = 760 mm Hg1 atm = 101.3 kPa = 760 mm Hg
A barometer measures atmospheric A barometer measures atmospheric pressure.pressure.
LiquidsLiquids Condensed states of matter – solids Condensed states of matter – solids
and liquidsand liquids
In liquids KE is high enough for In liquids KE is high enough for molecules to flow and take the shape of molecules to flow and take the shape of their container.their container.
Intermolecular attractions give liquids a Intermolecular attractions give liquids a definite volume. definite volume.
Evaporation – changing from liquid to Evaporation – changing from liquid to vapor at the surface - cooling processvapor at the surface - cooling process
Boiling point – temperature at which Boiling point – temperature at which the vapor pressure equals external the vapor pressure equals external pressure on the liquidpressure on the liquid
Volume – Volume Problems 2NO + O2 2NO2 How many liters of nitrogen dioxide are
produced when 34 L of O2 react?
22
2
2
2
2
22 NOL68
NOmol1
NOL4.22
Omol1
NOmol2
OL4.22
Omol1OL34
Volume – Moles Problems 2NO + O2 2NO2 How many moles of nitrogen dioxide
are produced when 34 L of O2 react?
22
2
2
22 NOmol04.3=×
Omol1
NOmol2×
OL4.22
Omol1×OL34
Solids Phase Changes
The general properties of solids reflect the orderly arrangement and fixed locations of their particles.
Crystal - regular geometric arrangement
Allotropes - (diamond, graphite) 2 or more different molecular forms of the same element in the same physical state
Phase changes Sublimation - solid to vapor Vaporization - liquid to vapor
(evaporation or boiling) Solidification - liquid to solid Melting - solid to liquid
STP – standard temperature and pressure - 0C and 1 atm
1 atm = 760 mm Hg so…
Hgmm1900atm1
Hgmm760atm5.2
Triple point – conditions ( temperature & pressure) at which solid, liquid, and vapor (gas) can exist in equilibrium.