Note Guide 8-1 Nature of Gases Kinetic Theory = all matter has tiny particles that are always moving --gas particles are molecules or atoms 3 assumptions of the kinetic theory 1. Particles in gases are small, hard spheres with basically no volume 2. Motion of gas particles is fast, constant and random --this is why gases fill their containers --also why we can smell gas when its on when it is shut off, eventually we can’t smell anymore of it.
3. All collisions between particles in a gas are perfectly elastic. Kinetic energy transferred from one particle to another without loss of energy Gas Pressure --comes from the force exerted by a gas per unit surface area of an object --What causes gas pressure? --simultaneous collisions of billions of rapidly moving particles in a gas with an object, --What do we call it where there are no particles? --a vacuum –empty space, no pressure
--Atmospheric pressure --very familiar to us --caused by the colliding atoms and molecules in the air --decreases as you move away from the earth because the density decreases --What measures air pressure? A barometer, of course --SI unit is the pascal (Pa) --normal atmospheric pressure = 100,000 Pa --STP (standard temp and pressure) –temp of 0 deg C and a pressure of kPa
Kinetic Energy and Temp --particles absorb energy and store it in the particle itself, but temp does not raise --the rest of the energy speeds up the particles, which increases the temp Average Kinetic Energy --particles of atoms and molecules at a given temp have wide range of kinetic energy. --most of the particles are in the middle range --physical state of matter does not change the average kinetic energy
Average Kinetic Energy and Kelvin Temp --as particles cool, we know they slow down. --theory says, they will eventually stop. = absolute zero --absolute zero has not been achieved in the lab, but close --Kelvin scale incorporates absolute zero, starting the scale there. --kelvin temp is directly proportional to the average kinetic energy of the particles of the substance.