# Gases and Atmospheric Pressure

Three types of motion and kinetic energy

-particles in a substance have three type of motion and therefore three types of kinetic energy -vibrational motion

-vibreational kinetic energy

-all particles have this type of energy

-rotational motion

-rotational kinetic energy

-particles in liquid and fases have some solids have this energy type -translational motion

-translational kinetic energy

-only particles in liquid and gas have this type of energy

Gases and Pressures Changes

Pressure

-recall: pressure id the force that is exerted on an object perunit of surface area -formula: pressure = force/area OR P = F/A

-the SI unit for force is newtons (N) and unit for area is square meters (m2) -therefore pressure has a unit of N/m2

-other units of pressure

-Pascal (Pa)

-millitetres mercury (mmHg)

-atmosphere

Atmospheric Pressure

-the gas molecules in our atmoshpere are pulled down towards earth's surface by gravity -these molecules exert pressure on all objects on earth

-earth's atmospheric pressure is therefore the force* that a column of air that exerts on earth's surface, divided by the area of earth's surface at the base of the column -therefore the force that the column of air exerts is its *weight -force is exerted equally in all directions

Atmospheric Pressure (atm)

-atmospheric pressure is how much pressure is being applied to something at sea level -column of air extending from sea level to the top of the atmosphere -cross-sectional area of 1m2

-mass of thie column of 10329 kg

-therefore, it weighs (force) 101325 N (because 10239 kg x 9.81 m/s2) -pressure = force/area

=101235 N/1 m2

=101235 N/m2

-therefore 101325 N/m2 will be equal to 1 atm

-this is the same concept as moles where 6.02 x 1023 particles = 1 mol Atmospheric Pressure and Altitude

-at high altituds, the atmospheric pressure is lower

-this is because the column pf air is smaller and therefore weight less -therefore...

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