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Agenda 02/15/2011

Agenda 02/15/2011. What are important properties of liquids?. OBJECTIVE: Compare and Contrast SOLIDS-LIQUIDS-GASES. HWK: CH 13 Vocab and Key Concepts DUE Tomorrow. Liquids. 13.2. What are Fluids?. Substances that can flow are referred to as fluids. Both liquids and gases are fluids.

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Agenda 02/15/2011

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  1. Agenda 02/15/2011 What are important properties of liquids? OBJECTIVE: Compare and Contrast SOLIDS-LIQUIDS-GASES HWK: CH 13 Vocab and Key Concepts DUE Tomorrow

  2. Liquids

  3. 13.2 What are Fluids? • Substances that can flow are referred to as fluids. Both liquids and gases are fluids.

  4. What determines the properties of Liquids? • The Attractive forces between molecules determines the properties of a liquid. • These are called intermolecular forces. • Inter = between • Molecular = molecules

  5. How does water compare to Ammonia? • Water has strong intermolecular forces. • The water molecules like to stay together. • This makes water have a high boiling point. (you have to heat it up to make a gas) • This makes water have a low vapor pressure. (it doesn’t want to evaporate)

  6. How does water compare to Ammonia? • Ammonia has weak intermolecular forces. • The ammonia molecules don’t like to stay together. • This makes ammonia have a lower boiling point than water. • This makes ammonia have a high vapor pressure. (it wants to evaporate) • Notice the smell?

  7. 13.2 What is Vapor Pressure? • Vapor pressure is a measure of the force exerted by a gas above a liquid.

  8. What Breaks apart intermolecular forces? • Vaporization - the change from a liquid to a gas below its boiling point. • Evaporation - vaporization of an uncontained liquid ( no lid on the bottle ).

  9. What is Evaporation? • Molecules at the surface break away and become gas. • Only those with enough KE escape • Evaporation is a cooling process. • It requires heat. • It is Endothermic.

  10. What is Condensation? • Change from gas to liquid • Achieves a dynamic equilibrium with vaporization in a closed system. • What is a closed system? • A closed system means matter can’t go in or out. (put a cork in it)

  11. What the heck is a “dynamic equilibrium?” • When first sealed the molecules gradually escape the surface of the liquid • As the molecules build up above the liquid some condense back to a liquid.

  12. Dynamic equilibrium • As time goes by the rate of vaporization remains constant • but the rate of condensation increases because there are more molecules to condense. • Equilibrium is reached when the rates of Vaporization and Condensation are equal.

  13. What really is Boiling? • A liquid boils when the vapor pressure = the external pressure • Normal Boiling point is the temperature a substance boils at 1 atm pressure. • The temperature of a liquid can never rise above it’s boiling point.

  14. 13.2 What changes Boiling Point? • The altitude can change the BP due to the change in pressure.

  15. 13.2 What measures Vapor Pressure? • A Manometer measures VP.

  16. 13.2 Section Quiz • 1. In liquids, the attractive forces are • very weak compared with the kinetic energies of the particles. • strong enough to keep the particles confined to fixed locations in the liquid. • strong enough to keep the particles from evaporating. • strong enough to keep particles relatively close together.

  17. 13.2 Section Quiz • 2. Which one of the following is a process that absorbs energy? • freezing • condensation • evaporation • solidifying

  18. 13.2 Section Quiz • 3. In a sealed gas-liquid system at constant temperature eventually • there will be no more evaporation. • the rate of condensation decreases to zero. • the rate of condensation exceeds the rate of evaporation. • the rate of evaporation equals the rate of condensation.

  19. 13.2 Section Quiz • 4. Where must particles have enough kinetic energy to vaporize for boiling to occur? • at the surface of the liquid • at the bottom of the container • along the sides of the container • throughout the liquid

  20. 13.2 Section Quiz • 5. The boiling point of a liquid • increases at higher altitudes. • decreases at higher altitudes. • is the same at all altitudes. • decreases as the pressure increases.

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