Science We need cotton balls Science We need cotton balls Do Now: 3/12 Can you bring some?Do Now: 3/12 Can you bring some?

HW: Read 16-1 and study for quizHW: Read 16-1 and study for quiz

1. Clear your table for the quiz 1. Clear your table for the quiz TodayToday ~ TTK 16:1 quiz and check~ TTK 16:1 quiz and check ~ Complete PPT w/notes: Water in the Air~ Complete PPT w/notes: Water in the Air

The Water CycleThe Water CycleThe transfer of water between the atmosphere and Earth’s surface.

1. Water evaporates from plants and bodies of water

2. Water condenses in the atmosphere and forms clouds

3. Clouds become saturated and water falls as precipitation to the surface

4. Water runs off surface into lakes, streams and oceans.

What is Humidity?What is Humidity?

1.1. The amount of water vapor in the air.The amount of water vapor in the air.

2.2. As water evaporates it becomes water As water evaporates it becomes water vapor.vapor.

3.3. Water vapor is invisible.Water vapor is invisible.

4.4. Warm air can Warm air can

hold more hold more

water vaporwater vapor

What is Relative Humidity?What is Relative Humidity?

1.1. Amount of water vapor in the air Amount of water vapor in the air compared to the amount of water the compared to the amount of water the air can hold. air can hold.

2.2. A percentage % A percentage %

3.3. Air holds all the water vapor it can Air holds all the water vapor it can

= Saturated = 100% RH= Saturated = 100% RH

Figuring Relative HumidityFiguring Relative Humidity__actual water vapor content (g/mactual water vapor content (g/m³)__ ³)__ X 100 = RH X 100 = RHsaturation water vapor content(g/m³)saturation water vapor content(g/m³)

1 m³ of air at 10ºC has 5g of water vapor1 m³ of air at 10ºC has 5g of water vaporbut, at this temperature it can hold 8gbut, at this temperature it can hold 8g

Calculate RH Calculate RH 5 g 5 g X 100 = 63% X 100 = 63% 8 g8 g

Air holds 13g but can hold 25gAir holds 13g but can hold 25g

13 g13 g X 100 = 52% X 100 = 52% 25 g25 g

Factors Affecting Relative HumidityFactors Affecting Relative Humidity

1.1. The amount of water vaporThe amount of water vapor

2.2. The temperatureThe temperature

If the water vapor stays the same:If the water vapor stays the same:

Temperature goes down RH% Temperature goes down RH% up up

Temperature goes up RH% Temperature goes up RH% down down

How does that work???How does that work???

At 20 At 20 ºC with 15g of water vapor RH = 100%ºC with 15g of water vapor RH = 100%Temperature goes up to 25 ºC air could hold 20gTemperature goes up to 25 ºC air could hold 20gSo… So… 15g (what it has) 15g (what it has) X 100 = 75% X 100 = 75% 20g (what it could have)20g (what it could have)

Temperature Temperature ºCºC Saturated gSaturated g

1515 1010

2020 1515

2525 2020

Measuring Relative HumidityMeasuring Relative Humidity

1. Measured with a 1. Measured with a psychrometerpsychrometer

2. Has two 2. Has two thermometersthermometers

* 1 wet bulb* 1 wet bulb

* 1 dry bulb * 1 dry bulb

Use the dry bulb temp Use the dry bulb temp and the chartand the chart

Determining Relative HumidityDetermining Relative Humidity

Use your book; page 484Use your book; page 484

Determine the relative humidity for the Determine the relative humidity for the following daysfollowing days

Day Day DryDryºCºC WetWetºCºC DifferDifferººCC

RH %RH %

MonMon 1616 1818

TueTue 1616 2020

WedWed 1818 2121

Determining Relative HumidityDetermining Relative Humidity

Day Day DryDryºCºC WetWetºCºC DifferDifferºCºC

RH %RH %

MonMon 1616 1818 22 8181

TueTue 1616 2020 44 6363

WedWed 1818 2121 33 7373

CondensationCondensation

1. Water vapor becomes a liquid1. Water vapor becomes a liquid

2. Happens when air is saturated2. Happens when air is saturated

3. Air cools to 100% relative humidity3. Air cools to 100% relative humidity

Dew PointDew Point

Temperature at which the air is saturated & condensation occursTemperature at which the air is saturated & condensation occurs

Where does the water on the outside of a glass Where does the water on the outside of a glass come from???come from???

The cold liquid in the glass cools the air outside of the glassThe cold liquid in the glass cools the air outside of the glassAir next to the glass reaches its Dew PointAir next to the glass reaches its Dew Point

Water vapor in the air condenses on the glass!Water vapor in the air condenses on the glass!

Quick Lab: pg 485Quick Lab: pg 485

What is the dew point temperature in the classroom today?What is the dew point temperature in the classroom today?

CloudsClouds

A collection on millions of tiny water droplets A collection on millions of tiny water droplets or ice crystalsor ice crystals

Warm air rises Warm air rises cools to dew point cools to dew point

water vapor condenses to a liquid/solidwater vapor condenses to a liquid/solid

Altitude and form/shapeAltitude and form/shape

Forms of CloudsForms of Clouds

Cumulus:Cumulus: Fluffy white with Fluffy white with flat bottomsflat bottoms

Stratus:Stratus: Form in layers, cover large Form in layers, cover large areas of skyareas of sky

Cirrus:Cirrus: Thin, feathery form at high Thin, feathery form at high altitudesaltitudes

Altitude of CloudsAltitude of Clouds

Cirro – forms at high altitudeCirro – forms at high altitude

made of ice crystalsmade of ice crystals Alto – middle altitudesAlto – middle altitudes

made of ice crystals & water dropletsmade of ice crystals & water droplets Low altitudes have no special prefixLow altitudes have no special prefix