Unit
Water! WAVE
weather
matters
Unit 2:
2: Water!
ENERGY
Bad Hair Day
What do we
measure with a
hygrometer?
(Humidity)
Humidity!
Humidity is the amount of Water vapor in the air.
Materials
Dry sponge (1 per group)
Bowl of water (1 per group)
Writing materials
Desiccant containers
(E.g., Damp Rid®)
Hygrometer instructions
(U2.L4.A5-pp.38-39)
Cardboard
Posterboard
Pushpin
Strand of human hair (12”)
Tape
Dime
Heavy book
Paperclip
Cup of hot water
Hawaii
Standards
Ready?
Elaborate
Cut cardboard into twelve-inch by nine-inch rectangles.
Cut poster board into triangular point about six inches long.
Set?
• Unit 1-Lesson 2-Activity 5: Making Changes (Changing States)
• Unit 2-Lesson 2-Activity 1: Warm, Warmer, Warmest (Add Heat)
• Unit 2-Lesson 3-Activity 2: Now you See It; Now You Don’t (Evaporation)
• Unit 2-Lesson 4-Activity 1: Weather or Not (Weather)
• Unit 2-Lesson 4-Activity 2: Feeling the Heat (Temperature)
• Unit 2-Lesson 4-Activity 3: Whooshing Winds (Wind)
• Unit 2-Lesson 4-Activity 4: Pressure Changes Everything (Air Pressure)
• Unit 2-Lesson 4-Activity 6: It’s Raining, It’s Pouring (Rainfall)
SC.K.1.1
SC.K.1.3
SC.K.2.1
SC.K.8.1
Go!
SC.1.1.1
SC.1.2.2
Develop Know-Wonder-Learn chart with students.
SC.2.1.1
SC.2.1.2
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Reef Pulse - U2 L4 A5
Think about it...
What is humidity?
Engage
Compare wet sponge to humid air in small groups.
• Squeeze a piece of very dry sponge.
What’s in a
Word?
Humidity comes
from the Latin word
humidus (moist).
How much water was in the sponge?
• Soak piece of sponge in a bowl of water.
Lift and hold it over bowl.
• Squeeze water back into bowl.
How much water was in the sponge?
Interesting
Fact
The more humidity
in the air, the slower
water evaporates.
Once air has all the
water vapor it can
absorb, no more
water evaporates.
Did You Know?
Humid air helps
smells travel farther!
Just for Fun
What are clouds’
favorite instrument?
Answer: Foghorns!
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33
Unit
Water! WAVE
weather
matters
Unit 2:
2: Water!
ENERGY
Bad Hair Day
Think about it...
What causes humidity?
Explore
Conduct Water in the Air experiment as a class.
• Ask a question,
What causes humidity?
• Do background research.
• Construct a hypothesis.
“If (I do this), then (this) will happen.”
• Test with an experiment.
Create a control: Place DampRid® packet into non-air conditioned room. Label it “No AC.”
Create a variable: Place DampRid packet into air conditioned room. Label it “AC.”
Discuss purpose of a desiccant. Discuss similarities and differences between two rooms.
Record amount of moisture each desiccant absorbs. Record measurements twice a week
for two weeks.
• Analyze data.
Discuss how air conditioners work. Discuss what is in the non-air conditioned room that
was missing from the air conditioned room.
• Communicate results.
34
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Reef Pulse - U2 L4 A5
Explain
Don’t you just hate those days that are hot, moist, and sticky? We call
those hot, moist, and sticky days humid weather. Meteorologists measure
humidity, or the amount of water vapor in the air. Air can only hold a certain
amount of water vapor before it condenses.
What is humidity?
Water vapor in the air! Air acts like a sponge. Water molecules fit into
the spaces between the air molecules. 0% humidity means the air has
no water vapor in it. 100% humidity means the air has so much water
that it could rain, just like your sponge did when it was full of water.
For clouds to form and rain to start, the air has to reach 100% relative
humidity.
What causes humidity?
Wator vapor and hot air! Water molecules evaporates into the air. Aunty
says more hot air equals more evaporation. More evaporation equals
more water vapor, which equals more humidity! The air conditioned
room in your experiment has cooler air, so you have less evaporation
and water vapors. The non-air conditioned room is hotter, therefore
more evaporation, more water vapors and more humidity!
Scientists Say...
...desiccants for
materials that can
absorb moisture
and keep things dry.
Desiccants are used
to absorb moisture in
baby diapers.
Did You Know?
High humidity
makes people feel
hotter outside in the
summer because
your sweat does not
evaporate as quickly
or as much as it
does when humidity
is low.
Interesting
Fact
It does not always
rain even with 100%
humidity. Fog has
100% humidity, for
example, but its
droplets do not fall
as rain.
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35
Unit
Water! WAVE
weather
matters
Unit 2:
2: Water!
ENERGY
Bad Hair Day
Think about it...
What tool do meteorologists use to measure humidity?
Elaborate
Create a hair hygrometer in small groups.
• Cut two slits in cardboard base about one-fourth inch apart and one-inch from
left side (A).
• Cut two slits along bottom of triangle
pointer about one inch from left side (B).
• Attach pointer to base with pushpin.
Make sure slits in pointer are facing toward the
bottom and aligned with slits in cardboard base.
• Wiggle pointer so it moves freely around
the pin.
• Slide hair through slits in base (A) and slits
in pointer (B).
Tape hair into each set of slits.
• Tape dime onto pointer, about one and a
half inches from left edge.
Hair should be between pushpin and dime.
• Arrange pointer so hair is slightly stretched
when pointer is perpendicular to hair.
Make sure pointer does not fall. Tighten if
necessary.
• Make three marks half an inch apart on
cardboard next to pointer tip. Label first mark “Dry”, label third mark “Humid”.
Pointer should point near middle mark when hair is taught.
• Compare hygrometer measurements outside to inside an air conditioned room.
How it works
Hygrometer! Aunty says hair stretches in humid weather. Have you ever noticed your
hair getting frizzy (or flat)? This happens because your hair absorbs the air’s moisture
and stretches! Stretching hair makes the arrow point lower. Since hair shrinks in low
humidity, the hair pulls down and moves the pointer upwards.
36
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Reef Pulse - U2 L4 A5
Evaluate
What do we measure with a hygrometer?
Test your hygrometer in small groups.
• Attach your hygrometer to the cover of a heavy book with a
paperclip.
• Place the hygrometer near a cup of steaming water.
Be careful not to touch the hot cup.
Web Resource
Check out your local,
national, or global
weather forecast.
www.intellicast.com
>> Forecast >>
Humidity
• Predict what will happen to your pointer.
How does humidity affect weather?
Invention
Center
Invented in 1783,
the hair hygrometer
proved so reliable
that only in the
1960s did someone
invent an electrical
one.
Assess
SC.K.1.1 Use the senses to make observations.
SC.K.1.3 Collect data about living and non-living things.
SC.K.2.1 Identify different types of technologies at home, in the classroom,
and/or in the world.
SC.K.8.1 Report and describe weather changes from day to day and over
the seasons.
Just for Fun
Watch a weather
forecast. What did
the meteorologist
say about humidity?
www.weather.com
SC.1.1.1 Collect, record, and organize data using simple tools, equipment,
and techniques safely.
SC.1.2.2 Describe a variety of changes that occur in nature.
SC.2.1.1 Develop predictions based on observations.
SC.2.1.2 Conduct a simple investigation using a systematic process safely
to test a prediction.
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37
HYGROMETER
U2.L4.A5 Bad Hair Day (Elaborate)
1.
2.
Start with one 12 by 9 inch cardboard
rectangle.
3.
Cut two slits in cardboard about 1/4 inch
apart and one inch from left side.
4.
Cut two slits along bottom of triangle
pointer about one inch from left side.
Attach pointer to base with pushpin.
Make sure slits in pointer are facing
toward the bottom and aligned with slits in
cardboard base.
38
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5.
6.
Wiggle pointer so it moves freely around the pin.
Slide hair through slits in base and slits in
pointer. Tape hair into each set of slits.
7.
8.
Tape dime to pointer (for weight),
about one and a half inches
from left edge. Hair should be
between pushpin and dime.
Arrange pointer so hair is
slightly stretched when pointer is
perpendicular to hair. Make sure
pointer does not fall. Tighten if
necessary.
Hawaii Coral Reef Initiative * U2.L4.A5 * www.reefpulsehawaii.com
Make three marks half an inch apart on
cardboard next to pointer tip. Label first
mark “Dry”, label third mark “Humid”.
Pointer should point near middle mark
when hair is taught.
39