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Materials
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Does a cloud form?
D
ice cubes
1. Fill one bowl abou t t fu ll with warm water.
Put nothing in the other bowl. Close both lids.
Put the sa me number of ice cubes on each lid.
2 plmtic bowls
o 2 . Observe after 1 minute, 5 minutes, and 10 mi nutes.
with lids
Cloud or No Cloud?
Observations
Bowl With Warm Water
Time
Bowl Without Water
After 1 min
After 5 min
After 10 min
Explain Your Results
,,.1'
3. Communicate Where did water con dense?
Did a cloud form ?. DISC USS.
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fj
I will know thol there
ore d ifferent types of
preci p itot ion and each
is connected w ith other
weather cond itions.
Words to Know
sleet
hail
Have you ever watched a cloud get larger? Have you
tried to see shopes in the clouds? Clouds come in mony
shapes and sizes. Remember that clouds form when water
vapor changes into tiny water droplets or ice crystals.
Whether a cloud is made of water droplets or ice crystals
depends partly on a ir tempera ture. The temperature
of a ir high in the douds is often much lower than the
tem pemture o f the niT close to the grou nd. Even on
summer days, many clouds are made of ice crystals.
The ice crystals a nd water droplets in clouds can join
together to make larger particles. Th e particles can get so
large Lh a l the gravitational fo rce due La the mass of the
particles can ca use th em to fa ll out of the cloud. This is
h ow precipitation fo rms.
1. Identify W hat are clouds made of? Underline a
statement or statements to support your answer.
2 . Write About It Use what you know about water on
Earth. Tell why clouds a re important.
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Precipitation
You may be surpri sed to learn thot most ra in in the
United States starts as snow. The temperature of the air
h igh a bove the ground is often below O"c. Clouds of ice
crysta ls form in the cold a ir. The ice crystals grow larger
until they sturt to fa ll as snowflukes. As they fa ll , the
crysta ls sometimes stick to other crystals a nd become
larger snowfla kes. If the tem pera ture of a lllhe air
between the cloud a n d th e ground is less tha n DoC,
th e ice crys tals will fa ll to the ground as snowfla kes.
The ice crysta ls from a cloud may cha n ge as they
fa ll through different layers of air. If the ice crystals fa ll
into air th at is warmer thon
aoc, they w ill m elt and fa ll
as rain . If the a ir near the ground is very cold, the rain
sometimes freezes before it hits the ground . The frozen
raindrops are sleet .
3.
® Draw Conclusions
Suppose you know the
a ir tempera ture from the
ground a ll the way to a
cloud is cold enough for
wa ter to freeze. The cloud
forms precipi tation. Wha t
co nclusion could you
d raw about the type of
preci p itation tha t fa lls?
Underline the facts that
helped you draw your
co nclusion .
Hail Formation
Sometimes, strong winds con blow upward through
a thunderstorm cloud. These winds blow raindrops back
up in to th e freezing a ir a t th e top of the cloud. This
creates a small piece of ice. As the ice is blown through
the cloud ma ny times, ma ny layers of water freeze on
it. Fina lly, it gets too hea vy for the winds to corry it back
up. This frozen precipitali on Lha Lfor ms in layers is coiled
hail. The ha ilstone fa lls to the groun d. Most ha ilstones
are a bout the size of a pea. Some can get bigger than
a baseball .
4. Summarize Wha t causes
layers to form in hai l?
examples of large
hoilstone s
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Rain l Sleetl and Snow Formation
s.
Ice crystals melt
as they fall through
a thin layer of
worm air high
above the ground .
Ice crystals
melt as they fall
through warmer
air. They fall
to the ground
as liquid drops.
\
,
/
•
If raindrops faU
for a longer time
through cold air,
they freeze and
to the ground as
frozen drops called
sleet.
G ive an Example
Three types of
preci pitation are ra in,
sleet, and snow. Do you
know two o ther types?
Li st them here .
6. Compare look a t the
cha rt. ~rc @ o ne way
rai n and sleet are a like.
Underline one way
sleet and snow a re a like.
If air between
the clouds and
the ground has a
temperature below
()!!C, ice crystals
fall as snow. They
reach the ground as
frozen crystals.
~
•
At·Home Lab
Rainmaker
Spray the inside of 0
pot lid with water. Keep
spraying until droplets
form. Use a toothpick to
push the smaller drops
together to form larger
drops. Continue until the
droplets run in a streom.
279
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Types of Clouds
7. Identify look outside .
Do you see any clouds?
If so , @rcl!J the nam es
of the cloud or clouds
on this page .
When you look at clouds in the sky, you may notice they
can look different from day to day. Different d oud types form
depending on the type of weather presen t. Clouds that fo rm
at different heights in the atmosphere have different names.
Here me five common types of clouds.
Cirrus
High-level clouds form m ore than 6 km above
the ground. This region overla ps the region for
midaltitude clouds. Ci rrus clouds are high -altitude
clouds that are often thin, wispy, and white.
Cumulonimbus
Clouds that grow vertically have rising air inside
them. The bases of these clouds may be as low as 1 km
{lbove the ground. The risi ng a ir may push th e to ps of
these clo uds higher tha n 12 km. Vertical clouds can
cause thunderstorms.
- ----~
~
----=.
Altocumulus
The bases of mid-level clouds are between 2 km
and 7 km above the ground. Altocumulus clouds a re
midlevel douds that look like small , puffy bolls. The
bottoms of the clouds can look dark because sunlight
may not reach them.
Stratus
Low-level clouds are often seen less than 2 km
above the ground. Stra tus clouds are low-level clouds
tha t cover the whole sky. They look dark because littl e
sunlight gets through the layer of clouds.
Fog
Fog is a cloud at ground level. M air near the
ground cools, wa ter vapor condenses into tiny droplets
and fo rms a cloud a t or near the ground. M more
droplets form and gel larger, the fog appears thicker.
280
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Skm
Sometimes many types of
douds may appear at the some
time. Combinations of d ouds
can h elp determine the weather
at a given place and ti me.
7km
6km
Skm
8. Classify Us ing the
information on the left,
4km
label the types of cloud s
in this picture.
"m
2km
\9, ~ se~uence ~nle Iheslep' laken fr~mwal~r vapor lasleel
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How are clouds and weather related?
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