LET IT SNOW:
An Investigative Unit on Snow Crystals
By Kelly Sortino
2002 QUEST Fellow
Students will learn the properties of snow crystals (specifically structure, shape and
symmetry) as well as how snow crystals are formed.
I.
BACKGROUND INFORMATION
Teachers—
The most basic form of an ice crystal is a hexagonal prism. This form occurs because
certain surfaces of the crystal, known as the growth facets, grow very slowly. The facets
exist due to the molecular structure of water. When water freezes into ice, the water
molecules stack together to form a regular crystalline lattice, and the ice lattice has sixfold symmetry. It is this hexagonal crystal symmetry that ultimately determines the
symmetry of snow crystals.
Simple six-fold symmetry is one thing, but how can some snow crystals be so complex
and symmetrical? This phenomenon has to do with the growth of a snow crystal in the
atmosphere. The growth usually begins with a dust particle (or some other
condensation nucleus) in a cloud, which absorbs some water molecules that form a
nucleus for the ice crystal. Faceting then causes the newborn crystal to quickly grow
into a tiny hexagonal prism. As the crystal grows larger, the corners often sprout tiny
arms, since they stick out a bit further into the supersaturated air and thus grow a bit
faster. Since the ambient atmospheric conditions are nearly identical across the crystal,
all six budding arms grow roughly at the same rate. The temperature seen by the snow
crystal is not constant over time, since the snow crystal is blown through different
temperatures of the cloud. Both temperature and supersaturation level affect the snow
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crystal’s growth. Thus, as a snow crystal blows around, it encounters different growth
conditions with time, thus growing into an intricate and symmetrical shape.
This explanation of snow crystal growth underlies the theory that “no two snow
crystals are alike.” The complex shape of a single arm is determined by the conditions
experienced by the snow crystal as it falls. Because each arm experiences the same
conditions, the arms tend to look alike, producing large-scale, intricate, six-fold
symmetric snow crystals. Since snow crystals all follow slightly different paths,
individual crystals all tend to look slightly different. The more complex the growth
history of the snow crystal, the more unlikely it becomes that any two crystals will have
experienced exactly the same history. Thus, it is unlikely to find even two complex
snow crystals that look exactly alike in Nature.
Students—
Basic understanding of the water cycle, cloud formation, symmetry and properties of a
triangle is recommended for this unit. For more information on classroom activities
relating to the water cycle and cloud formation, see the “Cloud in a Bottle” section of
this QUEST handbook.
II.
VOCABULARY
column: a long, pencil-shaped snow crystal
condensation nuclei: tiny particles of dust, smoke and salt that water vapor condenses
around in order to form water droplets in clouds
dendrite: a star-like snow crystal with many branching, fernlike arms
graupel: loose collections of frozen water droplets that become rounded pellets due to
riming; sometimes called “soft hail”
hail: large, solid chunks of ice
plate: a six-sided snow crystal shaped like a tiny stop sign
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rime: a deposit of ice formed when supercooled water droplets quickly freeze on
contact with an object
rotational symmetry: the condition where you can turn an object so that it looks exactly
the same
sleet: a snowflake that melts as it falls, but freezes again before reaching the ground
snow crystal: an individual, single ice crystal which often has six-fold symmetry and
grows directly from condensing water vapor in the air, usually around a nucleus
of dust, smoke or salt
snowflakes: loosely bound clusters of snow crystals that fall from a cloud
supercooled: the condition when a liquid remains in the liquid state even though its
temperature is below its freezing point
supersaturation: the condition which occurs in the atmosphere when the relative
humidity is greater than 100 percent
translational symmetry: the condition in which a figure can be divided by straight lines
into a sequence of identical figures
III.
PRE-ASSESSMENT ACTIVITY
Give students a piece of white paper and a pair of scissors, and ask them to cut
out a snowflake. Then, ask them to write down a description of their snowflake (such
as how many sides it has, what shape it is, and how many lines of symmetry, if any,
there are). You can also ask them to write down what they think a snowflake is made
of, how they think snowflakes are formed, and any experiences they have had with
snowflakes. Finally, have each student show their snowflake to the class and read what
they wrote aloud.
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IV.
DESCRIPTION OF INVESTIGATIONS
a.
Classification of Snow Crystals
Framing Question
How are snow crystals classified and what are the names and symbols of the
classification categories?
Materials
one envelope per student
glue sticks
unlined white paper
access to the internet
Procedure
1. Before you present this activity to the class, go on the Internet to find individual
pictures of snow crystals that W.A. Bentley photographed back in the late 1800’s and
early 1900’s. The website www.photolib.noaa.gov/historic/nws/nwind27.htm has a
good selection. Print out the different pictures, cut them up into squares and put about
15 pictures in each envelope. You will want to make sure that each envelope has at
least one picture of each different category of snow crystal.
2. Read the book Snowflake Bentley to your class aloud. Discuss what a biography is.
Go through the book and have the students point out the different types of snow
crystals that Bentley photographed.
3. Have the students go on the Internet and find archives of Bentley’s photographs. By
doing a basic search of “Bentley’s photographs,” the students can have access to a lot of
good pictures, like the ones below.1
1
These pictures were found at http://snowflakebentley.com/
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4. Have each student write down or draw the different kinds of snowflakes Bentley’s
photographed. Do any of them look similar? What is it called when we group together
things that have similar characteristics? (Classification)
5. Pass out one envelope to each student. Have each student open his/her envelope
and take the pictures of the snow crystals out. Have them classify their snowflakes into
as many groups as they want. Go around the room and see how many different
categories each student has. What are the classification characteristics of each group?
What things, other than snow crystals, can be classified? (Animals, plants, etc.)
6. Pass out a copy of the International Commission of Snow and Ice’s classification
chart of solid precipitation (found at
http://www.its.caltech.edu/~atomic/snowcrystals/class/isnow.jpg).2 Explain that
this is how scientists classify snow crystals.
7. Ask your students why they think the symbol is used for each category. Have them
identify the similarities in each classification.
8. Tell them that now they are going to classify some of Bentley’s snow crystals
according to this new classification system.
9. Give each student a piece of white paper and have them draw seven columns.
(Make sure they use a ruler.) At the top of each column, they want to write the category
name for each classification. Underneath that, they want to draw the classification
symbol for the respective category. See the chart below as an example.
2
This chart includes the seven categories of snow crystals (plates, stellar crystals, columns, needles,
spatial, dendrites, capped columns and irregular particles), as well as three additional types of frozen
precipitation: graupel, ice pellets (sleet) and hail. In order to not confuse your students, you might want
to cut off the bottom of the chart, so that you only have the seven categories of snow crystals listed.
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10. Ask your students to paste each picture of a snow crystal in the classification
category they think it belongs under.
11. Walk around the classroom and ask each student why they chose the classification
category they did. Have them defend their classification to others. Did the students
find any snow crystals that could possibly go under two categories? Discuss.
Name
Plates
Snow Crystal Classification Chart
Stellar
Columns Needles Spatial
Capped Irregular
Crystals
Dendrites Columns Particles
Symbol
Picture
Concepts to Discover
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b.
The students will learn about historical biography and primary sources for data.
(The photographs that they found on the Internet are really from one hundred
years ago, so it is a primary source for the types of snowflakes that fell back
then.)
The students will learn how to use the Internet for research.
The students will learn about the classification of snow crystals. They will learn
the seven classification categories and symbols, and will discover how to classify
the snow crystals themselves.
They will learn how to make and use a chart to organize information.
Preserving Snowflakes for Your Own Viewing3
Framing Question
How can we look at a snowflake under a microscope without it melting?
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The instructions for this activity are adapted from
http://www.teelfamily.com/activities/snow/science.html
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Materials
a snowy day
a box
a can of “Crystal Clear” Spray4
glass microscope slides
microscope
Procedure
1. Obviously, if you want to preserve a snowflake, it has to be snowing. However,
you’ll need to begin this experiment at least a day before it starts snowing. You’ll need
to leave the “Crystal Clear” spray can and glass slides in a box outdoors overnight so
that everything is exactly the same temperature as the falling snow. If the spray or
slides are just a little bit warm, the snowflakes will melt immediately when they land on
the slide.
2. If you haven’t read Snowflake Bentley to your class already, read it to them before
this experiment. Ask them about the techniques Bentley used to preserve the
snowflakes so that he could photograph them. What problems did Bentley initially run
into when he tried to preserve them? Ask them for their own suggestions as to how
they could preserve snowflakes.
3. Take the class outside and go to the box that you have left outside overnight. Spray
the “Crystal Clear” onto one of the glass slides and let some snowflakes fall on it. The
liquid plastic will slowly creep over the snowflakes and form a shell that replicates
every detail of each snowflake.
4. It will only take a few seconds to collect enough snowflakes on your slide. To keep
the slide from getting too much snow, put it back into the box outside.
5. Leave the wet slide in the box for several hours until the plastic hardens.
6. Later, when you bring the slide inside, the snowflakes will melt, but the plastic shell
will remain, preserving the shape of the snowflakes.
“Crystal Clear” is a liquid plastic that can be sprayed on a surface and then hardens to form a thin
transparent film.
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7. Once the replicas are dry, you can carefully examine the snowflakes under a
microscope without worrying about melting them.
8. Have the students draw pictures of their snowflakes and write about their
snowflakes in their science journals.
Note: This is not the only way to preserve snowflakes. Another effective method is using clear
acrylic spray paint from the hardware store or creating a Formvar (polyvinyl acetal resin)
solution in the lab. (Check out www.its.caltech.edu/~atomic/snowcrystals/preserve/preserve.htm
for more details on these preservation techniques.) If you are going to use a different
preservation solution, you might have to tweak the procedure of this experiment accordingly.
Concepts to Discover
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c.
The students will learn how they can preserve snowflakes, so that they can
observe the properties of snowflakes (shape, structure and symmetry) under a
microscope.
Growing your own Snow Crystals5
Framing Question
How do snow crystals grow, and how can we simulate this growth in a lab?
Materials
one (1) used 20-oz plastic Coke bottle
three (3) large-diameter Styrofoam cups6
one (1) small kitchen sponge (1/2 inch thick)
nylon fishing line (thinner is better; 1-pound test is good)
one (1) strong sewing needle
one (1) paper clip
a sharp knife (or pocketknife)
a pair of scissors
tap water
scotch tape
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Instructions for this activity were adapted from
http://www.its.caltech.edu/~atomic/snowcrystals/project/project.htm
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We seemed to get better results using 32 oz. Styrofoam cups that are wide and not very tall. These cups
are five inches tall and have a rim diameter of five inches, which is just about the right size to provide
clearance around the Coke bottle. Nevertheless, if you can’t find these exact containers, any Styrofoam
cups will work. (You can always cut a small hole in the bottom of the innermost cup in order to get the
Coke bottle to fit).
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some paper towels
one (1) hammer
a metal spoon
a hand-lens or magnifier
a lamp with ring stand
two (2) alcohol thermometers (optional)
dry ice7
Procedure
1. After rinsing out the Coke bottle and removing its label, use a sharp knife to cut the
bottle into two, about ½ inch above the bottom (shown in figure.)
2. Poke a hole in the center of the bottle bottom using the sewing needle.
3. Trace the bottle bottom onto the sponge and cut a small round sponge to fit inside
the bottle bottom.
4. Thread the fishing line into the sewing needle and push the needle through the hole
in the bottle bottom and through the sponge.
5. Attach the fishing line to the bottle bottom with a piece of tape, and tie a knot in the
other end to hold the paper clip. When the Coke bottle is inverted and reassembled, the
string should swing freely inside the bottle and should not touch any sides of the bottle
(shown in figure.)
6. Stack the three Styrofoam cups inside one another and place the inverted Coke bottle
inside the three Styrofoam cups, so that roughly ¼ of the bottle is standing above the
rim of the innermost cup. There should be about one inch of clear space between the
sides of the Coke bottle and the top edge of the Styrofoam cups.
7. Pull the top off the chamber (the bottle bottom + sponge), wet the sponge with tap
water, and replace.
We will now be dealing with the dry ice. Keep in mind that dry ice is very cold (about -60C), so
you’ll want to wear gloves when handling it. Other than being cold, it is perfectly safe, as it
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This is the only part of the experiment that is not readily available. You can find several sources for dry
ice on the internet or you can look in the Yellow Pages under Dry Ice. For a single experiment, you will
need ten (10) pounds of dry ice. If you plan to run several experiments at once, it’s probably sufficient to
have a few pounds per experiment. The price of dry ice ranges from $.50 to $1.00 per pound.
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consists of nothing more than solid carbon dioxide. The dry ice does not melt, but rather
sublimes (changes from a solid to a gas when warmed), producing carbon dioxide gas in the
process.
8. Put the dry ice inside two plastic grocery bags, and pound on it with a hammer to
crush it. This works best on a hard surface, like concrete or asphalt. Dry ice is much
softer than water ice, and it crushes very easily.
9. Put the crushed dry ice back into its Styrofoam cooler, and use a metal spoon to
transfer some of it into the Styrofoam cups around your chamber (shown in figure.) Fill
the cups to the top. It’s a good idea to wrap some paper towels around the top of the
Styrofoam cups in order to keep them from “sweating”.
10. Observe! Small ice crystals should begin forming on the string after 5-10 minutes,
and after 20-30 minutes, you should have a bunch of crystals. Shine the light on your
snow crystal chamber and use a magnifying glass for more detailed crystal viewing.
11. Have the students write down what they are observing and have them draw a
picture of what their crystals look like. After everyone has crystals, ask the students to
predict what will happen if they remove the top part of the chamber. Then have them
do that and tell them to write down their observations. (The snow crystals will turn
into water droplets.)
12. The students can try the experiment again by wiping the string clear with their fingers. They
can also insert an alcohol thermometer into the chamber to get temperature readings. (Attach the
thermometer to the inside of the bottle with tape.) The bulb of the thermometer would need to be
placed near the top of the ice crystal formation, since anything below that would be too cold for
the thermometer to register. Another reading can be made with another thermometer at a higher
level (which would show a higher temperature). Together, these readings would give some
indication that the temperature decreases downward in the chamber. As an extra extension, you
can have your students record their observations (in writing and drawing) every 5 minutes in a
science journal so that they can see the differences in temperature and crystal growth with
respect to time elapsed.
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Concepts to Discover
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What you see in the snow crystal growth chamber demonstrates what is
happening in the clouds when a snow crystal forms. Water evaporates from the
wet sponge and diffuses through the air in the bottle. When the water vapor
mixes with the cold air in the lower part of the bottle, the air becomes
supersaturated. Therefore, the water vapor will condense as ice onto any
convenient object, such as the string and the walls of the bottle.
In the growth chamber, we created supersaturated air, which has a relative
humidity of over 100%. This supersaturated air will not stay supersaturated
since water or ice will condense onto the walls and the humidity will dry to 100%
(the equilibrium or stable state). Supersaturated air is made all the time in the
atmosphere (typically when warm moist air mixes with cooler air) and this is
what is responsible for rain and snow.
Supersaturated air condenses into water droplets if the temperature is above 0C
and condenses to snow crystals if the air temperature is below 0C. (This is why
the snow crystals turned into water droplets when they were removed from the
chamber.) It is important to stress that snow crystals are not just frozen water
droplets. Instead, they are crystals that grow in supersaturated air that is below
freezing.
Supersaturated air does not automatically condense to produce droplets of rain
or snow. This only happens when there is some nucleation site on which
condensation can occur. In our growth chamber, we provide a string to nucleate
ice crystal growth. Individual water molecules bind to the microscopic scratches
and imperfections on the string, so once a small ice crystal gets started, it will
continue to grow. In the atmosphere, there are a lot of particles of dust, smoke or
sea salt. These make excellent nucleation sites, so rain droplets and snow
crystals usually each contain a dust particle on which the growth got started.
By doing temperature readings, the students can see that the bottom of the
chamber is cooler than the top. Since warm air is lighter than cool air, the air in
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the chamber does not undergo convection. The air at the top of the chamber
becomes saturated with water vapor because it is close to the sponge. Diffusion
happens because the air and water molecules are all moving and colliding with
one another, and in our growth chamber, diffusion causes the water molecules to
disperse from the top downward. As they diffuse down, they mix into a region
where the air temperature is much lower, with the result becoming
supersaturated air where the ice crystals can form.
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d.
Understanding the Hexagonal Structure of Ice Using Penny Patterns8
Framing Question
What shape does ice form and why does it form that shape?
Materials
100 pennies per group9
Scotch tape, double-sided tape, or poster mounts
Blank Charts (provided below)
Ring around center penny
1
2
3
4
5
# of pennies in that ring
Difference between ring 1 & ring 2
Difference between ring 2 & ring 3
Difference between ring 3 & ring 4
Difference between ring 4 & ring 5
The number of sides in a hexagon
Procedure
1. Challenge: Ask the students to take one penny and place it in the center of their desk.
Then, ask them how many pennies they can place around that penny so that each penny
is touching the center penny as well as the pennies on either side of it. (We will call this
a ring.) Have each group share their answers aloud and record their answers in the first
line of their chart. (Correct answer: 6. See below for visual diagram in Figure 1.) Ask
them how many sides the figure has and what shape the pennies form (6 sides form a
hexagon).
2. Have the students add another ring of pennies around the rim of the ring they just
created. Ask them to count how many pennies are in that ring and to record their
results in the chart. (See Figure 2.)
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This activity was adapted from a QUEST Weather and Climate II handout by Steve Carson.
For this activity, you can basically use anything that is circular and all the same size. Round colored
stickers, bottle caps, or flipped-over cups all work just as well.
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3. Keep doing this for up to 5 rings of pennies. Figure 3 shows the progression of all
five rings.
4. Now ask the students to remove the center penny that they started with. (Use scotch
tape, double-sided tape or a poster mount to pick the penny up.)
5. Tell the students that they want to remove pennies from throughout their five rings
so that each “hole” is surrounded by six pennies (like the one they just removed from
the center). This might be a little complicated to describe in words, so you might want
to distribute the diagram in Figure 4 which colors in all of the pennies that should be
removed.
6. Have the students recognize the six-fold (hexagonal) rotational symmetry of the
figure by having them draw the six lines of reflection on the diagram you distributed, as
shown in Figure 5.
7. Have the students recognize the translational symmetries by connecting the ring
around an opening on the diagram you distributed. Each ring of six pennies around an
opening can be shifted to be superimposed on successive rings, as illustrated in Figure
6.
Figure 1 (ring 1
Figure 3 (rings 1-5)
Figure 2 (ring 2)
Figure 4 (rings 1-5 with pennies removed)
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Figure 5 (six lines of reflection)
Teacher’s Answer Key for Charts
Layer around center penny
1
2
3
4
5
Difference between Layer 1 & Layer 2
Difference between Layer 2 & Layer 3
Difference between Layer 3 & Layer 4
Difference between Layer 4 & Layer 5
The number of sides in a hexagon
Figure 6 (translational symmetry)
# of pennies in that layer
6
12
18
24
30
(12-6) = 6
(18-12) = 6
(24-18) = 6
(30-24) = 6
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Concepts to Discover
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This activity offers a visual explanation as to why ice retains a hexagonal
symmetry in one plane as it “grows.” This activity also suggests that the internal
hexagonal symmetry of ice is what results in the hexagonal symmetry of snow
crystals.
By having the pennies representing water molecules, the students understand
that water molecules are circular (which in three-dimensions means that they are
spherical). The students also understand the basics about the molecular
structure of ice, since the touching pennies represent water molecules that are
held together by the attraction between the oppositely charged regions of the
molecule.
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e.
The open structure (the removal of some pennies) explains why ice is less dense
than water. This open structure also offers an explanation as to why snow
“crunches” (compresses) when you step on it.
This activity reinforces hexagonal rotational symmetry, shows six lines of
reflection and illustrates translational symmetry of each interior hexagon (i.e.
how the hexagons can be shifted).
This activity includes a chart component, which helps the students’ recording
skills. The chart includes math components, such as addition and subtraction,
and geometry components, such as symmetry of hexagons.
Hexagons: Snow Crystals as Math Tools
Framing Question
How can we use a snow crystal’s shape (a hexagon) to learn basic math concepts?
Materials
white paper
scissors
pencil
protractor
ruler
pattern blocks (specifically yellow hexagons and green triangles)
Procedure
Making a Hexagon (approximate method)
1. Start with a square piece of white paper. (If you are using regular 8.5 x 11 inch
computer paper, simply fold the top corner of the paper diagonally until it touches the
opposite bottom edge of the paper. Cut off the extra paper, a slender rectangle, and
unfold. You should have a square.)
2. Fold that square piece of paper diagonally in half (it should end up as a triangle.)
3. Make a small crease at the midpoint of the diagonal fold by bringing the two ends of
the fold together, then open back up.
4. Fold that triangle into three wedges from that midpoint, making the three angles at
the midpoint as equal as possible. The closer the angles are to being equal, the more
nearly the resulting hexagon will approximate an ideal regular hexagon.
5. Trim the edges opposite the midpoint in a straight line to form another triangle.
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6. Unfold your small triangle and you should end up with a hexagon.
7. Ask your students to use a ruler to measure each side of the hexagon and to record
their answers. (All of the sides should be equal.)
8. Ask your students to use a protractor to measure each of the interior angles of the
hexagon and to record their answers. (Each angle should measure 120.)
9. Since all of the angles are equal and all of the sides are equal, this hexagon is a
regular hexagon.
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The visual instructions below10 are for cutting out a snowflake. This procedure involves
folding the first triangle in half a second time creating a smaller triangle. This is
necessary to create the six-way symmetry of the snowflake.
Finding Triangles in a Hexagon
1.
Give each student or group one yellow hexagon pattern block and a handful of
green triangle pattern blocks. Ask them to find out how many green triangles will fit on
top of one yellow hexagon. (Answer: 6)
2. Have the students refer back to the hexagon that they made out of paper. Ask them
to use a ruler to draw the six triangles on the hexagon.
3. Ask the students to use a ruler to measure each of the sides of one of the triangles
and to record their answers. (All of the sides should be equal.) The measurements of
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Visual instructions found at http://www.teelfamily.com/activities/snow/art.html
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the sides of the triangle should be equal to the measurement of the sides of the hexagon,
since one side of the hexagon is the base of the triangle.
4. Ask the students to use a protractor to measure each of the interior angles of one of
the triangles. (Each of the angles should measure 60.) Since we know that the interior
angles of the hexagon each measure 120 and that the triangle divides that angle in half,
it makes sense that angle of the triangle should measure 60.
5. What is this figure called? A triangle with equal sides and equal angles is called an
equilateral triangle. The class should be able to conclude that 6 equilateral triangles
make up one regular hexagon, and should see the relationship between the
measurements of the sides and the angles.
Finding Even More Triangles in a Hexagon
1. Using the hexagon with the six triangles drawn on it, ask the students to use a ruler
to draw a line through the center of each one of those triangles, dividing it in half. Ask
them how many triangles, total, they now have in their hexagon. (Answer: 12)
2. Ask the students to use a protractor to measure each of the interior angles of one of
the new triangles they created. (The angles should measure 30, 60 and 90.)
3. Ask the students to add up the sum of the three angles for one of the smaller
triangles and to add up the sum of the three angles for one of the larger triangles.
(60+60+60 = 180and 30+60+90 = 180, respectively.)
4. What do they notice about the sum of each triangle? They both equal 180. Let them
know that the sum of the angles in all triangles always equals 180. If your students
don’t believe you, have them take a blank piece of paper and cut any size triangle they
want. Have them measure all of the interior angles with a protractor and add them up.
They will see that the sum equals 180, no matter what size the triangle is.
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Lines of Symmetry in a Hexagon
1. Using the same hexagon as before, have the students flip the hexagon over onto its
blank side
2. Have them fold the hexagon in as many ways as they can think of in which both
halves line up exactly. After they find a fold that works, ask them to use their ruler to
draw a line over that fold.
3. What is the most number of folds a hexagon can have so that both halves line up
exactly? Have the students count the number of lines they have drawn. The maximum
number of folds (or lines drawn) is six.
4. If a student didn’t have six folds, have them flip their hexagon over to the side that
has the 12 triangles drawn on it. The six lines that are drawn on that are exactly the
same as the six folds that work. Have each student fold their hexagon on each of the six
lines so that they see how both halves match up.
5. The number of lines they have drawn indicates how many lines of symmetry there
are. Each of the lines that are drawn is called a line of symmetry (or line of reflection).
A hexagon has six lines of symmetry, which means that it has six-fold symmetry.
Figuring out the Area of a Hexagon (for middle school students)
1. By using the hexagon with the 12 triangles drawn on it, students can discover the
area of a hexagon by knowing the formula for the area of a triangle. (It is recommended
that you go over the area of a triangle before this activity.)
2. By using the measurements of the sides from one of the 12 triangles, you already
have the measurements of the base and the height of the triangle.
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3. The formula for the area of a triangle is: (1/2) * base * height (abbreviated (1/2) b*h)
4. Since there are 12 triangles that make up this hexagon, the area of the hexagon would
be 12 * ((1/2) b*h), or 6 b*h.
Concepts to Discover
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V.
Students will learn how to use a protractor and take measurements of angles.
They will also learn how to use a ruler and take measurements of sides of a
hexagon and triangle.
Students will learn properties of a triangle (sum always equals 180 and the
formula for the area equals (1/2) b*h), and also properties of an equilateral
triangle (equal sides and equal angles).
Students will learn the properties of a regular hexagon (equal sides and equal
angles). They will also learn about lines of symmetry (specifically that hexagons
have 6 lines of symmetry), and they will learn how to use triangles to figure out
the area of a hexagon.
ASSESSMENT
The assessment activity for this unit on snow crystals is similar to the pre-assessment
activity. Have the students cut out a snow crystal. They should begin by making a
hexagon out of paper and cutting it while it is folded, so that it will have six sides and
also have six-fold symmetry like a real snow crystal (“Hexagons as Math Tools”
activity.) On a separate sheet of paper, have them write about how snow crystals are
formed (“How to Grow a Snow Crystal” activity) and why snow crystals have to be
hexagonal shapes (“Penny Pattern” activity). Have them classify their own snowflake
and write the symbol for that classification (“Classification of Snow Crystal” activity).
Have the students compare the snow crystals they cut out now to the snow crystals they
cut out as their pre-assessment activity. Have them tell you how their new snow
crystals are different (perhaps this one now has six-sides and is symmetrical). If they
can see how their new snow crystal is more like a real snow crystal than their first
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construction, then you know that they have learned something after all. Hang
everyone’s snow crystals around the room and turn the classroom into a Winter
Wonderland.
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VI.
SCIENCE EXTENSIONS
1. Measuring the Snow-to-Water Ratio
Have you ever heard the fun fact that it takes 10 centimeters of snow to make one
centimeter of water? See if it is true. Have the students take some containers to collect
snow. Record the level of snow on the container. Let the snow melt. How much water
is there? Introduce the idea of ratios and have the students create a snow-to-water ratio
from their findings.
2. Cloud in a Bottle
In order for your students to understand how a cloud is formed (and furthermore, how
a cloud is needed to make precipitation), have your students do the “Cloud in a Bottle”
activity in this QUEST handbook.
3. Ziplock Bag Water Cycle
In order for students to understand condensation, evaporation and precipitation, as
well as how snow is part of the water cycle, have your students do the “Ziplock Bag
Water Cycle” activity, found under the Science Extensions heading of the “Cloud in a
Bottle” activity in this QUEST handbook.
4. Grow Other Crystals
Refer to the book Crystals and Crystal Gardens You Can Grow or the website
http://www.teelfamily.com/activities/snow/boraxsnowflake.html in order to grow
your own crystals. Learn about salt and sugar crystals, as well. How do these compare
to snow crystals? Are there any patterns in these crystals as there are in snow crystals?
You can further investigate patterns in nature through the book What Shape is a
Snowflake?.
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VII.
CURRICULUM CONNECTIONS
Social Studies
1. Read the book The Language of Snow and learn about the Inuit people of Alaska.
How does snow affect their lives? How do the people and animals adapt to the snow?
The Kobuk tribe builds ookeviks (winter homes), which are structures that are built
partially underground. How is this different or similar to our homes? How does their
culture differ from ours?
2. Give the students a blank map and have them color in the different sections of the
world based on climate. Which of these climates gets snow? Which ones never get
snow? Why is this? Have a group of students choose a country in one of the regions
that does get snow and do a report that relates to amount of snowfall, adaptations to the
weather, etc. They can also do a comparison chart with the climate where they live.
Language Arts
Why do you think the Inuit people have over 20 words to describe “snow”? Have each
student pick one of the Inuit words for snow and write a poem in which they start with
the Inuit word, describe the snow scene and end with the English definition. The
students can use the book The Language of Snow as a research material. Below is a list
of Inuit words for snow along with their meaning:
Anniu
Api
Qali
Qamaniq
Siqoqtoaq
Anamana
Upsik
Mapsuk
Kaioglaq
Tumarinyiq
Kalutoganiq
Kimoaqtruk
Pukak
Salumaroaq
Natatgonaq
Quinzhee
Kanik
Siqoq
Falling snow
Ground snow
Snow on the boughs of trees
Bowl-shaped depression under tree
Sun crust
Space between drifts and obstruction
Wind beaten snow
Overhanging drift
Sharply etched wind eroded surface
Ripple type snow
Arrow shaped snow drift
Snow drift
Bottom snow layer (causes avalanches)
Smooth surface of fine particles
Rough surface of large particles
Snow shelter
Rime
Swirling or drifting snow
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Art
There are many arts and crafts activities to do before Winter Break that relate to winter
and snow. Have your students build a snow globe or make a three-dimensional Borax
snowflake. Websites such as http://www.daniellesplace.com/html/winter_crafts.html
and http://www.teelfamily.com/activities/snow/art.html have great snow-themed art
ideas.
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REFERENCES AND RESOURCES
a. Books
Kahl, Jonathan D. Wet Weather: Rain, Showers and Snowfalls. Minneapolis: Lerner
Publications Company, 1992. ISBN 0-8225-2526-7
(An exploration into snow, rain and other forms of precipitation, relating to cloud
formation and the water cycle.)
Maki, Chu. Snowflakes, Sugar and Salt: Crystals Close Up. Minneapolis: Lerner
Publications Company, 1993. ISBN 0-8225-2903-3
(Starting with snow crystals, this book investigates, in depth, different kinds of
crystals.)
Martin, Jacqueline Briggs. Snowflake Bentley. Boston: Houghton Mifflin Company, 1998.
ISBN 0-395-86162-4
(A wonderfully illustrated biography of Wilson Bentley, who was the first person to
photograph snowflakes.)
Stangl, Jean. Crystals and Crystal Gardens You Can Grow. New York: Franklin
Watts, 1990. ISBN 0-531-10889-9
(Although this doesn’t include snow crystals, this is a great tool for experiments if you
decide to do an extension from snow crystals to other crystals.)
Stewart, Ian. What Shape is a Snowflake? New York: W.H. Freeman and Company, 2001.
ISBN 0-7167-4794-4
(A mathematical exploration of patterns found in nature (such as snowflakes, a spider’s
web, desert dunes, honeycombs, etc.)
Williams, Terry Tempest and Ted Major. The Secret Language of Snow. San Francisco:
Sierra Club/Pantheon Books, 1984. ISBN 0-394-86574-X
(An information-packed book that explores the phenomenon of snow through the
vocabulary of the Inuit people of Alaska.)
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b. Websites
http://www.its.caltech.edu/~atomic/snowcrystals/
(CalTech Snow Crystal Laboratory—The best site out there for information about snow
crystals and their formation.)
http://www.teelfamily.com/activities/snow/
(Teel Family in Chugiak, Alaska—Plenty of educational resources relating to activities
and experiments about snow.)
http://nsidc.org/snow/
(The National Snow and Ice Data Center—A great website about the cryosphere, with
sections of questions and answers about snow, fun facts about snow and a glossary of
terms relating to snow.)
http://www.photolib.noaa.gov/historic/nws/nwind23.htm
(NOAA Photo Library—A great site for Bentley’s snowflake photographs.)
http://snowflakebentley.com/
(Official Snowflake Bentley website—Information about Bentley’s life, his hometown
and his photographs.)
http://www.nancypolette.com/LitGuidesText/snowflake.htm
(Nancy Polette—A literature guide to Snowflake Bentley with questions and activities
relating to the book.)
http://www.units.muohio.edu/dragonfly/snow/index.htmlx
(Ice and Snow—Follow a scientist’s expeditions in Antarctica, while learning about ice
and snow.)
http://www.northstar.k12.ak.us/schools/joy/creamers/Kits/lesson.html
(Fairbanks North Star Borough School District—A 5th grade sample lesson plan that
utilizes a snow crystal investigation kit.)
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VIII. RELATED NEW JERSEY CONTENT STANDARDS
5.1 Scientific Processes
5.2 Science and Society
A. Cultural Contributions: Students can explore this through the Social Studies
curriculum connections to the Inuit people.
B. Historical Perspectives: Students read, write and talk about Snowflake
Bentley in a historical context.
5.3 Mathematical Applications
A. Numerical Operations: Students do estimates, measurements and
computations of quantities.
B. Geometry and Measurement: Students use different tools of measurements to
learn about the geometry of hexagons and triangles.
C. Patterns and Algebra: Students identify patterns and symmetries in
snowflakes.
D. Data Analysis and Probability: Students use tables and charts to represent
data.
5.4 Nature and Process of Technology
A. Science and Technology: Students distinguish between lab-simulated snow
crystal growth and how snow crystals really occur in nature.
B. Nature of Technology: Students demonstrate how measuring instruments are
used to gather information.
C. Technological Design: In “Snowflake Preservation” and “Snow Crystal
Growth”, students choose materials and a design to identify a problem and
develop a solution.
5.5 Life Science
B. Diversity and Biological Evolution: Through the Social Studies curriculum
connections, students recognize different kinds of plants and animals that live
in different parts of the world and how they adapt.
5.6 Physical Science—Chemistry
A. Structure and Properties of Matter: Students use a magnifier and microscope,
draw and describe details of an experiment, classify objects by properties, and
recognize that water can exist as and transform into solid, liquid or gas.
5.8 Earth Science
B. Atmosphere and Water: Students learn about seasonal changes, patterns in
the weather, the water cycle (evaporation, condensation and precipitation),
cloud formation, weather measurements and the formation of snowflakes.
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