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Native Pathways to Education
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Observing Snow

Water: The Stuff that Makes Snowflakes

 Water: The Stuff that Makes Snowflakes
Adapted from
C.W. Fetter, "Applied Hydrology"


Using the overhead transparencies provided in the Snow Curriculum Kit, the instructor introduces the class to the basic ideas of the hydrologic cycle, water chemistry, crystal formation, and how a snowflake is formed. There are many ideas introduced verbally, visually, and physically in this section. It lays the ground work for the entire program. Students are encouraged to fill in the blank arrows on page 2 of the Snow Journal and begin working on their glossary terms during the discussion. Throughout the program students will follow along in the snow journals, recording key terms and ideas.

One of the key concepts is that the planet's water moves in a cycle and that the total amount of water on the earth stays fairly constant. This idea that almost all water is recycled has some interesting ramifications. Ask the students what they think some of the implications are, and listen for some wonderful, intuitive answers!

A good tool for teaching the hydrologic cycle is to ask the students to name a small local creek, and try to trace the water through its cycle using the local example. In eastern Denali National Park, the local weather pattern mostly originates as moisture that has evaporated from ocean water in the Gulf of Alaska. The moisture condenses into clouds and typically moves inland and north. Rain and snow, precipitation, fall when warm moist air condenses as it encounters the Alaska Range.

Of the resulting runoff, some infiltrates through to the ground water table, some is actually trapped on the surface by the frozen permafrost layer below, and some flows into the creeks as runoff. One creek, located in eastern Denali Park, Riley Creek, drains the high mountainous regions. Riley Creek flows into the Nenana River, which flows into the Tanana, which flows into the Yukon, which eventually flows into the Bering Sea. There the water becomes a source for more evaporation and the resulting cloud formation, and the hydrologic cycle continues. Attaching this scientific concept to a concrete local example makes it not only understandable, but real to the students.


Overhead Transparencies

Overhead Projector

Overhead Pens

Snow Journals


A - 4, 15


D 3


B - 1


age 11-14
1, 3
age 15-18
1, 2, 4


Snow Journal icon
Snow Journal
pg. 2

This journal icon indicates where students use the Snow Journals in conjunction with the lesson or activity

English /
B - 3

A - 1, 2

How Water Behaves

All matter, including water, is made up of molecules. Molecules are stable units composed of smaller particles called atoms. They are the smallest units of matter that still retain the characteristics
of that material.

Although invisible to the eye, molecules are always moving. The energy content, or amount of motion of the molecules determines the state of matter (solid, liquid, or gas.)

Matter does not always have to change phases in sequence. Sublimation is the process where water, depending upon conditions, can change from solid to gas or gas to solid without ever passing through the liquid state.

A water molecule.

A water molecule. The 120 degree angle of the two hydrogen atoms flanking the oxygen atom is the secret to the symmetry of the water crystal lattice.

Activity: Phase Change Exercise
  • Have the entire class stand up, teacher too! (Shake off those cobwebs). First wiggle and move as much as possible while still keeping your feet firmly planted. This motion represents the molecular vibration of a typical solid.
  • Next let's increase the energy, imagine a bit of heat was added. Now everyone gets to move as much as possible, but can only move one foot at a time. This motion represents the liquid phase, note that the individual molecules are occupying more space and the room suddenly seems more crowded.
  • In the gas phase simulation, students can move freely and each individual is encouraged to move the entire length of the room. Caution! The gas phase can be a bit unrulely if you have an especially rambunctious group.
  • It also fun to try sublimation where the students imitate the motion of gas molecules, and then quickly switch to solid molecule motion without the intermediate liquid phase. Remember sublimation can go in both directions!

This is a good exercise to introduce the concept of density. Intuitively it is obvious that the gas is far less dense, intuitively lighter per unit area.

Most matter expands and becomes less dense as it changes phases from solid to liquid to gas.

Water is Different! Freezing Water and Crystal Formation

It is probably not an exaggeration to state that much of life on the planet as we know it is due to the unique quality of water becoming less dense as it freezes.

Does ice sink or float?

It floats, of course, because it is less dense than water. This phenomenon allows lakes and rivers to freeze from the top, protecting vital life processes in the water beneath the ice.

The unique floating quality of ice is due to the way the molecules arrange themselves as water crystals are formed in the freezing process. The arrangement of water molecules is only semi-structured in the liquidstate. When water freezes, these molecules assume an orderly arrangement with fixed positions for the oxygen atoms. The hydrogen atoms provide the bonds which hold together this structure called the crystal lattice. The shape, relative size, and the electrical charges of the constituent atoms determine that water molecules will crystallize during the freezing process into regularly occurring six sided patterns. The structure of ice crystals is responsible for the endlessly beautiful six-sided shape of snowflakes.

This diagram shows the crystal lattice of ice

This diagram shows the crystal lattice of ice next to free-moving water with a transition zone of slush. Water's unusual propensity to be less dense as a solid than as a liquid reflects the fact that hydrogen atoms shift slightly in angle as ice crystals form, forcing an increase in volume.
From "Everyday Science Explained" by Curt Suplee

Activity: How Dense is Snow?

Quart-sized jars
Pencil and Markers

Collect snow and fill a jar calibrated from 1 -100. Have students mark their initials on the jar where they predict the water line will be after thawing. This can be calculated into a percentage, and used to introduce the idea of density as it relates to snow. For example if the water line is at 22 after the snow has melted, the density would be 22/100 or 0.22 or 22%. Water is the standard for density at a value of 1 kg/liter.

The snow of interior Alaska typically measures in at a density of 0.18 to 0.24 kg/liter, or 18% -24% water content.

age 11-14


A -1


A 1, 2

The Life and Times of a Snowflake

All precipitation starts as water vapor in the atmosphere. This water vapor is a product of evaporation and condensation as previously discussed in the hydrologic cycle section. As water vapor rises, it usually experiences cooling. Some of this water vapor will condense into clouds composed of either ice crystals or water droplets that remain liquid although the air temperature is below freezing. In some casesthis supercooled water can remain liquid in temperatures down to minus 40° Fahrenheit.

Snow crystals begin as minute ice particles which have formed around condensation nuclei in the atmosphere. These nuclei are essential to the formation of snow crystals because smooth sided water molecules will slip by one another unless there is a solid, rough, surface to hold them together. There is an abundance of dust in the atmosphere, but only certain kinds of material attract water vapor. These nuclei may consist of dust particles or even minute particles of sea salt. Forest fires, smokestacks, automobile exhaust, volcanic eruptions, and even barbeques emit particles that will anchor water molecules to their surfaces.

 from "Discover Nature in Winter" by Elizabeth Lawlor

from "Discover Nature in Winter" by Elizabeth Lawlor

Snowflakes are made up of very complex ice crystals. One ice crystal is made up of one quintillion water molecules. The classic snowflake is a little star of great beauty. The key to the regularly repeating six sided patterns lies in the atomic structure of water, the H2O molecule. Recall the arrangement of the atoms of a water molecule, with two hydrogen stuck onto a big oxygen like ears on Mickey Mouse's head. The secret of the snowflake lies in the angle created by the hydrogen atoms at the center of the oxygen atom. It is 120 degrees. As a consequence of this structure, ice forms a stiff six-sided lattice. A crystal, enlarged by the condensation of water on its surface, preserves its original symmetry. The famous mathematician Descartes was the first to record the observation that the snowflake branches grow only in a direction parallel to the adjacent arms, always at 60 degrees to their stems. Beside the feathery stellar shapes, there are needles, columns, capped columns, and many other shapes.

 from "Discover Nature in Winter" by Elizabeth Lawlor

from "Discover Nature in Winter" by Elizabeth Lawlor

The particular shape of a snowflake is determined by the many types of atmospheric conditions it encounters on its journey from the clouds to the ground. The predominant factors are temperature and vapor content. Because specific environmental conditions vary greatly, it is rare that two snow flakes will take the exact same journey; and so they say, "No two snowflakes are alike."

A-1, 2, 4

A Picture is Worth a Thousand Words

This graph reveals how temperature and water vapor determine the particular type of snow crystal that will be formed.

This graph reveals how temperature and water vapor

A - 4, 6

age 11-14
2, 4

Snow Journal icon
Snow Journal
pg. 7

Air Temperature

From: "Winter, An Ecological Handbook" by James Halfpenny and Roy Ozanne.
Cited from Perla and Martinelli, 1976 & Mango and Lee 1966.

Activity: Practice Reading the Graph

  • Show students that just one illustration can represent a wealth of information!
  • Finding snowflakes on the graph is a great exercise in graph reading, an important basic skill.
  • Ask students under what temperature and water vapor conditions Stellar crystals are formed.
  • Next try Solid Bullets, and then, Needles. They will soon understand how it works!
  • Next ask if it is warm and moist, or warm and dry what crystals will form.
  • How does this graph correlate with the Freshly Fallen Snow Chart in the Snow Journal on page 6?


Atom: The smallest possible unit of an element. Atoms of the same or different elements combine to form molecules. Atoms remain essentially unchanged during chemical reactions.

Condensation: A change from gas to liquid by cooling.

Condensation Nuclei: Particles of dust that act as a nucleus, an essential component in the crystallization of water to a solid.

Crystal: A homogenous solid formed by a repeating 3-D pattern of atoms or molecules. The orderly arrangement forms a pattern called a crystal lattice.

Density: The degree to which the atoms of a substance are packed. Density is the measure of mass per unit of volume. Density = Mass/ Volume

Evaporation: A change from liquid to gas by heating.

Gas: State of matter having no definite shape or size.

Ground Water: Water moving through permeable subsurface rock.

Ice Crystal: Water in its solid crystalline state forms a regularly occurring sixsided lattice of H2O molecules. The arrangement of the atoms and electrical charges determine the lattice pattern.

Infiltration: The process of water filtering into the earth's surface.

Liquid: State of matter having a definite size, but not shape.

Molecule: Chemical units composed of one or more atoms. Molecules are smallest particle of a substance having all the properties of that substance.

Precipitation: Water that falls as rain or snow.

Solid: State of matter having a definite shape and size. The normal condition of a solid is a crystalline structure.

Sublimation: The direct passage of a substance from solid to gas or gas to solid without appearing in the intermediate liquid state.

Supercool: To cool a liquid below the normal freezing point without solidification

Surface Runoff: The process of water from precipitation moving downhill into lakes, streams, and rivers.







Observing Snow

The Four Corners of Life
Water: the Stuff that Makes Snowflakes
Snow on the Ground Changes Through Time
Exploring Native Snow Terms
Glacier Investigations
Open Note Review
Bibliography & Resources



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Last modified August 17, 2006