Warm Up 3/11/08Warm Up 3/11/08

1)1) What are the three states of matter?What are the three states of matter?

a. Gas, liquid, solida. Gas, liquid, solid b. Gas, liquid, vaporb. Gas, liquid, vapor

c. Vapor, liquid, solidc. Vapor, liquid, solid d. Gas, vapor, solidd. Gas, vapor, solid

2)2) What is the change of state from a gas to a What is the change of state from a gas to a liquid called?liquid called?

3)3) True or False: Heat is released when water True or False: Heat is released when water evaporates.evaporates.

Answers: 1) a. 2) condensation 3) FalseAnswers: 1) a. 2) condensation 3) False

Water in the AtmosphereWater in the Atmosphere

Chapter 18, Section 1Chapter 18, Section 1

Water in the AtmosphereWater in the Atmosphere

Precipitation –Precipitation – any form of water that falls any form of water that falls from a cloudfrom a cloud

When it comes to understanding When it comes to understanding atmospheric processes, water vapor is the atmospheric processes, water vapor is the most important gas in the atmospheremost important gas in the atmosphere

Water vapor makes up only a small Water vapor makes up only a small fraction of the gases in the atmosphere, fraction of the gases in the atmosphere, ~0-4 percent by volume~0-4 percent by volume

PrecipitationPrecipitation

Concept CheckConcept Check

What is the range in volume percent of What is the range in volume percent of water in the atmosphere?water in the atmosphere?

Atmosphere is nearly 0 to about 4 percent Atmosphere is nearly 0 to about 4 percent water by volume.water by volume.

Water’s Changes of State: Solid to LiquidWater’s Changes of State: Solid to Liquid

The process of changing state requires that The process of changing state requires that energy is transferred in the form of heatenergy is transferred in the form of heat

When heat is transferred to a glass of ice water, When heat is transferred to a glass of ice water, the temperature remains a constant 0the temperature remains a constant 0ºC until the ºC until the ice is meltedice is melted

Latent Heat –Latent Heat – does not produce a temperature does not produce a temperature change; stored energychange; stored energy

Latent heat plays a crucial role in many Latent heat plays a crucial role in many atmospheric processes; it is the major source of atmospheric processes; it is the major source of energy for thunderstorms, tornadoes, and energy for thunderstorms, tornadoes, and hurricaneshurricanes

Solid to LiquidSolid to Liquid

Water’s Changes of State: Liquid to GasWater’s Changes of State: Liquid to Gas Evaporation –Evaporation – the process of changing a liquid to a the process of changing a liquid to a

gasgas The energy absorbed by the water molecules during The energy absorbed by the water molecules during

evaporation gives them the motion needed to escape evaporation gives them the motion needed to escape the surface of the liquid and become a gas (latent heat the surface of the liquid and become a gas (latent heat of evaporation)of evaporation)

““evaporation is a cooling process” means that it takes evaporation is a cooling process” means that it takes incredible energy to evaporate water, usually it comes incredible energy to evaporate water, usually it comes from whatever object it is evaporating from (i.e. you!)from whatever object it is evaporating from (i.e. you!)

Condensation –Condensation – the process where water vapor the process where water vapor changes to the liquid statechanges to the liquid state

For condensation to occur, water molecules must For condensation to occur, water molecules must release their stored heat energy, latent heat of release their stored heat energy, latent heat of condensation, equal to what is absorbed during condensation, equal to what is absorbed during evaporationevaporation

EvaporationEvaporation

Water’s Changes of State: Solid to GasWater’s Changes of State: Solid to Gas

Sublimation –Sublimation – the conversion of a solid the conversion of a solid directly to a gas, without passing through directly to a gas, without passing through the liquid statethe liquid state

This is the process you see when you This is the process you see when you watch dry ice, the “smoke” is actually the watch dry ice, the “smoke” is actually the solid carbon dioxide becoming a gassolid carbon dioxide becoming a gas

Deposition –Deposition – the conversion of a vapor the conversion of a vapor directly to a soliddirectly to a solid

This happens when water vapor is This happens when water vapor is deposited as frost on cold objectsdeposited as frost on cold objects

SublimationSublimation

Changes of StateChanges of State

Concept CheckConcept Check

What happens to heat during a change of What happens to heat during a change of state?state?

Heat is absorbed or released, depending Heat is absorbed or released, depending on the change of state.on the change of state.

SaturationSaturation As water begins to evaporate from the water As water begins to evaporate from the water

surface, a small increase in pressure can be surface, a small increase in pressure can be detected in the air abovedetected in the air above

This increase is a result of the motion of the This increase is a result of the motion of the water molecules that were added to the air water molecules that were added to the air through evaporationthrough evaporation

As more and more molecules escape from the As more and more molecules escape from the water surface, the pressure in the air increases water surface, the pressure in the air increases steadilysteadily

Saturated –Saturated – the number of vapor molecules the number of vapor molecules returning to the surface of a body of water returning to the surface of a body of water equals the amount leavingequals the amount leaving

When saturated, warm air contains more water When saturated, warm air contains more water vapor than saturated cold airvapor than saturated cold air

SaturationSaturation

Concept CheckConcept Check

How does the temperature of air influence How does the temperature of air influence its ability to hold water?its ability to hold water?

When saturated, warm air contains more When saturated, warm air contains more water vapor than cold air.water vapor than cold air.

Relative HumidityRelative Humidity Relative Humidity –Relative Humidity – ratio of the air’s actual ratio of the air’s actual

water-vapor content compared with the amount water-vapor content compared with the amount of water vapor air can hold at that temperature of water vapor air can hold at that temperature and pressureand pressure

Relative humidity indicates how near the air is to Relative humidity indicates how near the air is to saturation, rather than the actual quantity of saturation, rather than the actual quantity of water vapor in the airwater vapor in the air

Relative humidity can be changed by adding or Relative humidity can be changed by adding or removing water vapor from the airremoving water vapor from the air

When the water-vapor content of air remains When the water-vapor content of air remains constant, lowering air temperature causes an constant, lowering air temperature causes an increase in relative humidity, and raising air increase in relative humidity, and raising air temperature causes a decrease in relative temperature causes a decrease in relative humidityhumidity

Changing Relative Humidity by Changing Relative Humidity by Changing TemperatureChanging Temperature

Changing Relative Humidity by Changing Relative Humidity by Changing Specific HumidityChanging Specific Humidity

Variations in Temperature and Variations in Temperature and Humidity in Washington D.C.Humidity in Washington D.C.

Concept CheckConcept Check

List two ways that relative humidity can be List two ways that relative humidity can be changed.changed.

Relative humidity can be changed by Relative humidity can be changed by adding or removing water vapor or by adding or removing water vapor or by changing temperature.changing temperature.

Dew PointDew Point Dew Point –Dew Point – the temperature to which a the temperature to which a

parcel of air would need to be cooled to parcel of air would need to be cooled to reach saturationreach saturation

If the same air was cooled further, the air’s If the same air was cooled further, the air’s excess water vapor would condense, excess water vapor would condense, typically as dew, fog, or cloudstypically as dew, fog, or clouds

For every 10For every 10ºC increase in temperature, ºC increase in temperature, the amount of water vapor needed for the amount of water vapor needed for saturation doublessaturation doubles

High dew-point temperatures indicate High dew-point temperatures indicate moist air, and low dew-point temperatures moist air, and low dew-point temperatures indicate dry airindicate dry air

Dew Point TemperatureDew Point Temperature

Measuring HumidityMeasuring Humidity

Hygrometer –Hygrometer – device to measure relative device to measure relative humidityhumidity

One type of hygrometer, the One type of hygrometer, the psychrometer, consists of two identical psychrometer, consists of two identical thermometers mounted side to sidethermometers mounted side to side

The amount of cooling that takes place in The amount of cooling that takes place in the psychrometer is directly proportional to the psychrometer is directly proportional to the dryness of the airthe dryness of the air

PsychrometerPsychrometer

AssignmentAssignment

Read Chapter 18 (pg. 504 – 522)Read Chapter 18 (pg. 504 – 522) Do Chapter 18 Assessment #1-30 (pg. 527-Do Chapter 18 Assessment #1-30 (pg. 527-

528)528)