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13. 1 and 13.2 The Behavior of Gases and Liquids

13. 1 and 13.2 The Behavior of Gases and Liquids. Kinetic Molecular Theory. Kinetic Molecular Theory (KMT) Kinetic Energy is energy of motion. KMT discusses the motion of particles. Kinetic Molecular Theory. Kinetic Molecular Theory (KMT) 3 ideas of the KMT

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13. 1 and 13.2 The Behavior of Gases and Liquids

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  1. 13. 1 and 13.2The Behavior of Gases and Liquids

  2. Kinetic Molecular Theory • Kinetic Molecular Theory (KMT) • Kinetic Energy is energy of motion. • KMT discusses the motion of particles.

  3. Kinetic Molecular Theory • Kinetic Molecular Theory (KMT) • 3 ideas of the KMT • Matter is made of tiny, submicroscopic particles. • Particles are in constant motion. • Particles collide elastically. This means they do not lose energy. They actually bounce off each other like nothing happened.

  4. KMT continued • Review of states • Solids: • definite shape, definite volume • Liquids: • indefinite shape, definite volume • Gases: • indefinite shape, indefinite volume

  5. tight particles, low KE, medium particles, medium KE, lose particles, high KE,

  6. Atmospheric Pressure • Atmospheric pressure-the pressure from collisions of atoms and molecules in the air with other objects. • Standard pressure values: • 1 atm • 760 torr • 760 mmHg • 101.3 kPa

  7. Increase temperature increase KE. Decrease temperature decrease KE. What if we stopped movement of particles altogether? Absolute zero can be defined as temperature in which all motion ceases to exist. Temperature vs. KE

  8. Bill Nye says it well

  9. 1.Flow 2. Definite volume 3. Evaporates Space between particles 2. Attraction b/t particles hold them together 3. Particles that have enough kinetic energy to overcome attractive forces willleave Liquids CharacteristicsWhy?

  10. Questions… • How could you speed up the rate of evaporation? 2. If you have particles with high KE and low KE, which one will have particles escape first? 3. What is the process called when a liquid is heated to a temperature that causes the particles to escape?

  11. Questions… • How could you speed up the rate of evaporation? Add more heat 2. If you have particles with high KE and low KE, which one will have particles escape first? High 3. What is the process called when a liquid is heated to a temperature that causes the particles to escape? Evaporation

  12. Evaporation of Liquids • Evaporation occurs only at the surface of a liquid. • It can occur at any temperature as long as the substance is a liquid. • We can speed up evaporation though…

  13. Boiling of Liquids • Boiling begins within the liquid. • The process of boiling creates bubbles that rise to the surface. • The temperature has to be above the BP of the substance. • This speeds up evaporation.

  14. Boiling Point of Liquids • The BP is related directly to vapor pressure. • Liquids boil when the vapor pressure is equal to the atmospheric pressure. • Vapor pressure is a force exerted by the gaseous phase of a two phase (gas/liquid or gas/solid) system.

  15. Munster vs. Denver • We are at 1 atm or 101.3 kPa of atmospheric pressure at sea level. • What is the BP of water here at sea level? • 100.0 °C • Denver (above sea level) has an atmospheric pressure of only 85.3 kPa.

  16. Questions…. • Would the BP of water be lower or higher in Denver? • Would it take longer to cook an egg here in Munster or Denver? • If you increase the pressure, what happens to your boiling point?

  17. Questions…. • Would the BP of water be lower or higher in Denver? • Lower, 95.0°C • Would it take longer to cook an egg here in Munster or Denver? • Denver • If you increase the pressure, what happens to your boiling point? • Increases

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