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Chapter 9: Gases. States of Matter. Kinetic Molecular Theory (Review). solid liquid gas (vibrational) (vibrational, (translational) rotational,
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Kinetic Molecular Theory (Review) solid liquid gas (vibrational) (vibrational, (translational) rotational, translational)
What is unique about “gas” state? • There is space between molecules so size of molecules DOES NOT affect the VOLUME a gas occupies. • The volume is affected when the space between the molecule changes by • Temperature - Unit = oC, Kelvin (K) • Pressure – force/unit area - Unit = N/m2 = Pa kPa * old units: psi, mm Hg, torr, atm *Standard temp and Pressure (STP) = 0oC & 101.325 kPa
Kinetic Molecular TheoryAssumptions for Gases • Each gas molecule is separate, surrounded by empty space • Particles move rapidly in straight lines, often colliding with each other and the container walls. • There is no loss of energy when 2 particles collide • In the gas phase, there are no attractive forces between particles • At any given temperature, the average kinetic energy of the particles in gases is the same. http://www.chm.davidson.edu/vce/kineticmoleculartheory/basicconcepts.html
In a container filled with gas there will be collisions between the particles and particles and also collisions between particles and the container walls. • The collisions between the particles and the walls is known as GAS PRESSURE. • The greater the amount of collisions with the wall in a given amount of time, will give a greater pressure.
As the volume decreases, the particles collide more frequently with the containers walls. Therefore, the particles will exert greater force on the walls. • Therefore, PRESSURE INCREASES. * Pressure = force/area = force per surface area
Boyle’s Law Simulation & Graph http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/boyles_law_graph.html