Agenda 02/15/2011

Agenda 02/15/2011Agenda 02/15/2011

HWK: CH 13 Vocab and Key ConceptsDUE Tomorrow

HWK: CH 13 Vocab and Key ConceptsDUE Tomorrow

What are importantproperties of liquids?What are important

properties of liquids?

OBJECTIVE: Compare and ContrastSOLIDS-LIQUIDS-GASES

OBJECTIVE: Compare and ContrastSOLIDS-LIQUIDS-GASES

LiquidsLiquids

What are Fluids?What are Fluids?

• Substances that can flow are referred to as fluids. Substances that can flow are referred to as fluids. Both liquids and gases are fluids.Both liquids and gases are fluids.

13.2

What determines the properties of What determines the properties of Liquids?Liquids?

The Attractive forces between molecules The Attractive forces between molecules determines the properties of a liquid.determines the properties of a liquid.

These are called These are called intermolecular forcesintermolecular forces.. Inter = betweenInter = between Molecular = moleculesMolecular = molecules

How does water compare to How does water compare to Ammonia?Ammonia?

WaterWater has has strongstrong intermolecular forces. intermolecular forces. The water molecules like to stay together.The water molecules like to stay together. This makes water have a This makes water have a high boiling high boiling

pointpoint. (you have to heat it up to make a . (you have to heat it up to make a gas)gas)

This makes water have a This makes water have a low vapor low vapor pressurepressure. (it doesn’t want to evaporate). (it doesn’t want to evaporate)

How does water compare to How does water compare to Ammonia?Ammonia?

AmmoniaAmmonia has has weakweak intermolecular forces. intermolecular forces. The ammonia molecules don’t like to stay The ammonia molecules don’t like to stay

together.together. This makes ammonia have a This makes ammonia have a lower boiling lower boiling

point than waterpoint than water.. This makes ammonia have a This makes ammonia have a high vapor high vapor

pressurepressure. (it wants to evaporate). (it wants to evaporate) Notice the smell?Notice the smell?

What is Vapor Pressure?What is Vapor Pressure?

• Vapor pressureVapor pressure is a measure of the is a measure of the force exerted by a gas above a liquid.force exerted by a gas above a liquid.

13.2

What Breaks apart intermolecular What Breaks apart intermolecular forces?forces?

VaporizationVaporization - the change from a liquid to - the change from a liquid to a gas below its boiling point.a gas below its boiling point.

EvaporationEvaporation - vaporization of an - vaporization of an uncontained liquid ( no lid on the bottle ).uncontained liquid ( no lid on the bottle ).

What is Evaporation?What is Evaporation?

Molecules at the surface break away Molecules at the surface break away and become gas.and become gas.

Only those with enough KE Only those with enough KE

escapeescape Evaporation is a cooling Evaporation is a cooling process.process. It requires heat.It requires heat. It is It is Endothermic.Endothermic.

What is Condensation?What is Condensation? Change from gas to liquidChange from gas to liquid Achieves a dynamic equilibrium with Achieves a dynamic equilibrium with

vaporization in a closed system.vaporization in a closed system. What is a closed system?What is a closed system? A closed system means A closed system means

matter can’t go in or out. matter can’t go in or out. (put (put a cork in it)a cork in it)

When first sealed the When first sealed the molecules gradually molecules gradually escape the surface of the escape the surface of the liquidliquid

As the molecules build As the molecules build up above the liquid some up above the liquid some condense back to a condense back to a liquid.liquid.

What the heck is aWhat the heck is a ““dynamic equilibrium?dynamic equilibrium?””

As time goes by the rate of As time goes by the rate of vaporizationvaporization remains remains constantconstant

but the rate of but the rate of condensationcondensation increases increases because therebecause there

are more molecules are more molecules to to condense.condense.

EquilibriumEquilibrium is reached is reached when the rates of when the rates of Vaporization and Vaporization and Condensation are equal.Condensation are equal.

Dynamic equilibriumDynamic equilibrium

What really is Boiling?What really is Boiling? A liquid boils when the A liquid boils when the

vapor pressure = the external pressurevapor pressure = the external pressure Normal BoilingNormal Boiling point is the temperature a point is the temperature a

substance boils at 1 atm pressure.substance boils at 1 atm pressure. The temperature of a liquid can never rise The temperature of a liquid can never rise

above it’s boiling point.above it’s boiling point.

What changes Boiling Point?What changes Boiling Point?

• The The altitudealtitude can change the BP due to can change the BP due to the change in the change in pressurepressure..

13.2

What measures Vapor Pressure?What measures Vapor Pressure?• A A ManometerManometer measures VP. measures VP.

13.2

13.2 Section Quiz13.2 Section Quiz

1.1. In liquids, the attractive forces areIn liquids, the attractive forces are• very weak compared with the kinetic energies of very weak compared with the kinetic energies of

the particles.the particles.• strong enough to keep the particles confined to strong enough to keep the particles confined to

fixed locations in the liquid.fixed locations in the liquid.• strong enough to keep the particles from strong enough to keep the particles from

evaporating.evaporating.• strong enough to keep particles relatively close strong enough to keep particles relatively close

together.together.

13.2 Section Quiz13.2 Section Quiz

2.2. Which one of the following is a process Which one of the following is a process that absorbs energy?that absorbs energy?• freezingfreezing• condensationcondensation• evaporationevaporation• solidifyingsolidifying

13.2 Section Quiz13.2 Section Quiz 3.3. In a sealed gas-liquid system at In a sealed gas-liquid system at

constant temperature eventually constant temperature eventually • there will be no more evaporation.there will be no more evaporation.• the rate of condensation decreases to zero.the rate of condensation decreases to zero.• the rate of condensation exceeds the rate of the rate of condensation exceeds the rate of

evaporation.evaporation.• the rate of evaporation equals the rate of the rate of evaporation equals the rate of

condensation.condensation.

13.2 Section Quiz13.2 Section Quiz 4.4. Where must particles have enough kinetic Where must particles have enough kinetic

energy to vaporize for boiling to occur?energy to vaporize for boiling to occur?• at the surface of the liquidat the surface of the liquid• at the bottom of the containerat the bottom of the container• along the sides of the containeralong the sides of the container• throughout the liquidthroughout the liquid

13.2 Section Quiz13.2 Section Quiz

5.5. The boiling point of a liquid The boiling point of a liquid • increases at higher altitudes.increases at higher altitudes.• decreases at higher altitudes.decreases at higher altitudes.• is the same at all altitudes.is the same at all altitudes.• decreases as the pressure increases.decreases as the pressure increases.