science

• Gas


  • Can be found around us
  • Part of our daily living
  • Tools use principles governing gas properties
• Principal general properties of gases

  • Gases are compressible
  • Gases fill any container that they occupy
  • Different gases mix completely
  • Gases expand in the presence of heat
  • Gases do not settle in their container
• Kinetic molecular theory (KMT)


  • Gases consist of tiny, discrete molecules, each of which has a mass
  • Molecules are relatively far apart with empty spaces between them
• Gas molecules

  1. In constant, rapid, random motion

  2. Move in straight lines until they collide with other molecules, or with the walls of the container
• Gas pressure


  Result of the number of collisions of gas molecules in a unit of time
• Factors that increase gas pressure

  1. Forcing more gas into the container

  2. Decreasing the volume of gas

  3. Heating the gas in a closed container
• Kinetic energy of gas molecules


  Increases by heating the gas and decreases by cooling it
• Collisions of gas particles are perfectly elastic
• Scientific postulates of kinetic molecular theory

  • Gas consist of very small particles, each of which has a mass
  • The distances separating gas particles are relatively large
  • Gas particles are in constant, rapid, and random motion
  • Collisions of gas particles with each other or with the walls of the container are perfectly elastic
  • The average kinetic energy of gas particles depends only on the temperature of the gas
  • Gas particles exert a force on one another, in other words, the attractive forces between gas particles are so weak that the model assumes them to be zero
• Pressure


  The force exerted by a gas on the wall of its container
• Volume


  The amount of space that a substance or object occupies
• As pressure increases


  Volume of the gas decreases
• As pressure decreases


  Volume of the gas increases
• Boyle's law


  The relationship between the volume of a given quantity of a gas and its pressure, where volume is inversely proportional to pressure at constant temperature
• Boyle's law is expressed using the equation: P1V1 = P2V2
• Units for measuring pressure and volume


  • Pressure: mm Hg, atm, Pa, kPa
  • Volume: mL, L
• Solving a sample problem using Boyle's law

  1. Given: P1 = 750 mm Hg, V1 = 500 mL, P2 = 650 mm Hg

  2. Find: V2
• Applications of Boyle's law in real life

  • Chest respirator
  • Sphygmomanometer
• roberts boyle is british chemist discovered the boyles law
• chest respiratory a machine used in the treatment ood patients with respiratory difficulties
• sphygmanometer a device used to measure blood