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The Kine(c Molecular Theory States of Matter—Gases, Liquids and Solids The Kine(c Molecular Theory Literal interpretation: The theory of moving molecules The Kine(c Molecular Theory   Observations to support the theory:  
Diffusion in gases and liquids Movement of substances from an area of high concentration to one of lower concentration Ability of a gas to spread out and fill a container  
Brownian Movement
The observable movement of particles due to collisions with moving molecules.   The theory explains these observations   The theory describes the differences between gas, liquids and solids   The theory explains the gas laws The Kine(c Molecular Theory The Kine(c Molecular Theory   Major points: Supports the concept of an ideal gas…   An ideal gas is one that perfectly fits all the assumptions of the kinetic-­‐molecular theory.   Do not actually exist—in theory this is how they would behave: 1. Gases are made of tiny particles far apart relative to their size: Volume occupied by the molecules is inconsequential Volume is mostly space Explains why gases are compressible 1
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The Kine(c Molecular Theory The Kine(c Molecular Theory   2. Gas particles are in continuous, rapid, random motion As a result there are collisions with other molecules or with the wall of the container   3. There are no attractive forces between molecules Creates pressure Increase in temperature increases the movement of the molecules and thus the pressure exerted by the gas   4. Collisions between gas particles and between particles and container walls are elastic collisions.  
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Collisions in which there is no net loss of total kinetic energy Kinetic energy can be transferred between two particles during collisions Total kinetic energy remains the same as long as temperature remains the same The Kine(c Molecular Theory 1. Gases are made of tiny particles far apart relative to their size 2. Gas particles are in continuous, rapid, random motion 3. There are no attractive forces between molecules under normal conditions of temperature and pressure 4. Collisions between gas particles and between particles and container walls are elastic collisions. 5. All gases at the same temperature have the same average kinetic energy. The energy is proportional to the absolute temperature. Gas molecules are moving too fast Gas molecules are too far apart Intermolecular forces are too weak The Kine(c Molecular Theory  
under normal conditions of temperature and pressure The Kine(c Molecular Theory   5. All gases at the same temperature have the same average kinetic energy. The energy is proportional to the absolute temperature. Absolute temperature = Kelvin temp scale Ke = ½ mv2 Ke = the kinetic energy m = mass v = the velocity
The Kine(c Molecular Theory   Applies only to ideal gases   Most gases behave like an ideal gas under normal conditions   Real gases   Deviate from ideal behavior   Due to intermolecular interaction (H2O, NH3)   Gases with little attraction between molecules…He/H2/N2   High pressure   Low temperature 2
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The Kine(c Theory and Changes of State Kine(c Molecular Theory and Changes of State   Gases—Attractions are   Attractions between particles in strength: insignificant   Least
  Liquids—Attractions are London dispersion forces Dipole-­‐dipole interaction more important leading to a more ordered state Hydrogen bonding   Solids –Attractions are most important with an ordered state   Greatest Metallic, Ionic and Covalent network Kine(c Molecular Theory and Changes of State Kine(c Molecular Theory and Changes of State   Changes of state occur with a change in temperature or pressure   Particles of a substance overcome (or succumb) to intermolecular attraction  Involves energy Kine(c Molecular Theory and Changes of State   Consider the evaporation of a liquid:   Temperature= the average kinetic energy   Some molecules have more kinetic energy than others   These molecules escape and become gas molecules Solids, liquids and gases can undergo various changes in processes that are either endothermic or exothermic Kinetic Molecular Theory and Changes of State   Evaporation will occur in closed container also except……   As the liquid evaporates the space above starts to fill with gas molecules until it can hold no more   Gas will start to condense. 3
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Kine(c Molecular Theory and Changes of State   Eventually the rate of evaporation will equal the rate of condensation   Two processes will occur   Vapor molecules above the liquid will collide with each other and the container………………………
and exert a pressure. simultaneously with no net change   Equilibrium vapor   State of Equilibrium pressure!!! Kine(c Molecular Theory and Changes of State   Every liquid has a specific vapor pressure at a given temperature.   Reflection of the strength of the intermolecular bonding between molecules   Vapor pressure also increases with temperature Kine(c Molecular Theory and Changes of State   Equilibrium vapor pressure is (EVP) used to define boiling point, BPt   Boiling point is the temperature at which the equilibrium vapor pressure equals atmospheric pressure Kine(c Molecular Theory and Changes of State   Boiling requires a continuous supply of energy……..  
Water boils at 100oC and the temperature does not change….even though there is a continuous supply of energy….. Kine(c Molecular Theory and Changes of State   Boiling point of water is 100 oC only at 760mm Hg   When atmospheric pressure is > 760 mm Hg the boiling pt is > 100.   When atom0spheric pressure is <760mm Hg the boiling pt is <100 Kine(c Molecular Theory and Changes of State   Same is true when ice melts…… 00C   It melts (or freezes) at   At this temperature there is a state of equilibrium   Temp will not change if both phases are present   Where does the energy go? 4
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Kine(c Molecular Theory and Changes of State   Energy is can be added continuously, but the temperature does not change   Energy is used to change the physical state…this requires a lot of energy!! 5