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Gas State: Basics, Pressure and Its Measurement
Lecture 8
Aristotle’s Elements
Gases
everywhere.
Some important gases
Oxygen O2
Nitrogen N2
Argon Ar
Carbon dioxide CO2
Methane CH4
Ammonia NH3
Chlorine Cl2Ethylene C2H4
Hydrogen H2
Helium
Hydrogen sulfide H2S
Carbon cycle
Gases are important.
All gases
has remarkably similar physical behavior.
The molecules
are much farther apart in the gas
than in either the liquid or the solid.
What distinguishes gases from liquids and solids:
Gas volume changes greatly with pressure.Gas volume changes greatly with temperature.Gases have relatively low viscosity.Most gases have relatively low densities under normal conditions.Gases are miscible.
Pressure (P)
is defined as the force exerted per unit of surface area:
Pressure=Force/Area
Pa=N/m2
Gases exert pressure
on all surfaces with which they make contact.
Evangelista Torricelli (1608-1647), Italian scientist
Torricelli’s experiment
Manometers are devices
used to measure the pressure of a gas in an experiment.
Some widely used manometers
A sample problem
on converting units of pressure.
THE END