Particle motion: atoms move in a straight line between collisions.

• An O₂ molecule in the air travels about 443 m/s (about 1700 km/hour) at 25 ^oC.
   
• The diameter of an O₂ is about 0.339 nanometers. Each molecule travels about 314 times its own diameter between collisions. At this rate, each oxygen molecule has over four and a half billion collisions per second.

Pressure: the force of particles striking a surface.

• The SI unit for pressure is the pascal, named for Blaise Pascal.
   
• The pascal is a derived SI unit equal to 1 Newton / m²

  (1 N = (1 kg)(1 m) / s²)

• The average air pressure at sea level is 101.325 kilopascals (kPa).

  Scientists call this average "standard atmospheric pressure".

Temperature: a measure of the average kinetic energy of the particles of matter.

• Kinetic energy is the energy an object has because of its motion.
   
• The SI units for energy is the joule.
   
• The joule is a derived SI unit equal to (kilograms) (meters) / s².
   
• KE = ¹/₂ mv²
   
• The calorie is sometimes used to describe heat. This unit is defined as the amount of heat needed to raise the temperature of one gram of water one Celsius degree.

  A food Calorie (notice the capital C) is 1000 regular calories, one Kilocalorie.