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Gases chemistry

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Gases  chemistry Gases chemistry Presentation Transcript

  • GASES
  • GasesHow does the KMT explain the behavior of gases? Kinetic Molecular Theory Has 3 parts: 1. Particle Size 2. Particle Motion 3. Particle energy In your groups, describe the properties of a gas using these three Review Physical States of Matter categories.
  • Gases Kinetic Molecular Theory: Particle Size  Gases consist of small particles separated by empty space.  The volume of the particle is small compared to the empty space.  Gases have no attractive or repulsive force.
  • Kinetic Molecular Theory•Particle Motion •Gas particles travel in constant, random motion. •Particles move in a straight line until the collide with another particle, or with the wall of its container. •Gas particle collisions are elastic.
  • Kinetic Molecular Theory Particle Energy  The kinetic energy of a gas particle is determined by mass and speed.  Gas molecules have high kinetic energies.
  • Properties of Gases Gases can be compressed  Compression is the ability to decrease the volume of a gas.
  • Warm Up Use the Kinetic Molecular Theory to explain the following:  Why do gases expand to fill their containers?  Why do gases have a low density? Why can gases be compressed, but solids and liquids cannot?
  • How are pressure and volume of a gas related? Question: What might happen to the gas in a balloon if you decreased its volume by squeezing it?
  • How is pressure defined? Pressure: force exerted per unit area. Gas molecules exert pressure when they collide with the walls of their container. As the number of gas molecules in a container increases, pressure _______________.
  • Measuring Pressure SI unit for pressure: pascal At sea level, the average air pressure is 101.3 kPa Air pressure is measure in atmospheres (atm)  1 atm = 101.3 kPa
  • Pressure Evangelista Torricelli, one of the first to discover atmospheric pressure, once said, "We live submerged at the bottom of an ocean of the element air." The Earths gravitational field is pulling on air, and this pull, or "pressure" of air, is called atmospheric pressure. Boyles Law Simulation
  • Boyle’s Law Relates Pressure to Volume If temperature and amount of gas particles are held constant, pressure will ___________ when volume decreases. The farther you are from sea level, atmospheric pressure decreases. Why would it be difficult to breathe in the mountains? Why do Olympic athletes often train at high altitudes? Why are airplane cabins “pressurized” before take off?
  • Boyle’s Law P1V1 = P2V2 P1 and V1 represent initial conditions P2 and V2 represent final conditions A scuba diver blows a 0.75 L air bubble 10 m under water. As it rises to the surface, the pressure goes from 2.25 atm to 1.03 atm. What will be the volume of air in the bubble at the surface?
  • Boyles Law and Breathing How does Boyle’s Law explain breathing?  As your diaphragm moves downward, the lungs expand.  As your diaphragm moves upward, the lungs shrink in volume. Why does air enters the lungs when you inhale, and exit the lungs when you exhale? When a person is ill with emphysema, parts of the lungs lose their elasticity and become enlarged. Why does this affect their breathing? Why are beginning scuba divers taught to never hold their breath when they are under water?
  • Warm up A balloon contains 30 L of helium gas at sea level. As the balloon is released in to the sky, the volume increases to 42 L of helium. What is the final pressure of helium gas?
  • How are volume and temperature of a gas related?
  • Charles’ Law Why do breads and muffins rise when baked? Why is a higher temperature required to bake at higher altitudes? What happens to a balloon in liquid nitrogen? What happens to soda that is left in a car on a hot summer day? Why is laying on an air mattress more comfortable that laying on the ground?
  • Charles’ Law V1 = V2 T1 = T2A helium balloon in a closed car occupies a volume of 2.32 L at 40 degrees celsius. If the car is parked on a hot day and the temperature inside rises to 75 degrees celsius, what is the new volume of the balloon, assuming the pressure remains constant?
  • Charles’ Law V1 = V2 T1 = T2A helium balloon in a closed car occupies a volume of 2.32 L at 40 degrees celsius. If the car is parked on a hot day and the temperature inside rises to 75 degrees celsius, what is the new volume of the balloon, assuming the pressure remains constant?2.32 = V240 = 75 (2.32)(75) = 40(v2) 4.35 L = V2
  • Practice What volume will the gas in the balloon occupy at 250 K? 4.3 L 350 K
  • How are Pressure and Temperature Related? Why do chefs use a “pressure cooker”?
  • Combined Gas Law What is held constant in the combined gas law? You can derive each Gas Law from the Combined Gas Law.
  • Combined Gas Law A gas at 110 kPa and 30 degrees C fills a flexible container with an initial volume of 2.00 L. If the temperature is raised to 80 degrees C and the pressure increases to 440 kPa, what is the new volume?
  • Combined Gas Law A gas at 110 kPa and 30 degrees C fills a flexible container with an initial volume of 2.00 L. If the temperature is raised to 80 degrees C and the pressure increases to 440 kPa, what is the new volume?
  • Practice An unopened, cold 2.00-L soda bottle contains 46 mL of gas confined at a pressure of 1.3 atm at a temperature of 5 degrees Celsius. If the bottle is taken on a submarine which sinks to a depth at which the pressure is 1.52 atm and the temperature is 2.09 degrees C, what will be the volume of gas in the bottle?
  • Graphic Organizer Complete the following graphic organizers: Effect Effect EffectPressure increaseVolume increaseTemperature decreasesLaw Boyle’s Charles’s CombinedFormulaWhat is heldconstant?
  • The Ideal Gas Law How is the amount of gas particles related to pressure, temperature and volume?
  • Warm Up Each balloon below contains 1 L of gas. Answer the following:  Are the volumes equal?  Are the number of molecules equal? The moles?  Are the masses equal? H2 C3H8 He CH4 N2 CO2
  • Avagadro’s Principle The KMT assumes that gas particles are far apart. Therefore, size of a gas particle is negligible Does size (mass) of a gas molecule determine volume of a gas?
  • Avagadro’s Principle NO!!!!! 1,000 Krypton gas particles occupy the sameAvagadro proposed……. volume as 1000 helium gas particles. (At the same temperature and pressure of course)
  • Avagadro’s Principle Equal Volumes of gas at the SAME temperature and pressure contain equal numbers of particles.