Gases:  Pressure 
Barometer - apparatus used to measure pressure; 
derived from the Greek "baros" meaning "weight" 
  • Created by Evangelista Torricelli in 1646 
    • Inverted a tube filled with mercury into a

    • dish until the force of the Hg inside the tube
      balanced the force of the atmosphere on the
      surface of the liquid outside the tube 

Next:  "Laws"