How Snowflakes Form Worksheet Download

Look at that tiny white star falling from the sky! It is a snowflake, and it is soft and cold. Most snowflakes have six sides.

How does a snowflake get its shape? High up in a cloud, water in the air freezes onto a tiny speck of dust. The ice grows and grows into a snowflake.

A man named Wilson Bentley loved those tiny ice stars. In 1885 he took pictures of snowflakes in Vermont. He saw that no two looked exactly alike!

Have you ever caught a snowflake on your mitten? Look close, and you will see a tiny, lacy star! Every snowflake begins high up in a very cold cloud.

Up in that cloud, a tiny speck of dust floats. Water vapor, which is water floating in the air, freezes onto it. Soon the ice grows six sparkly arms as it falls.

Those six arms can grow in many different ways. In 1885, Wilson Bentley took close-up photos of snowflakes in Vermont. He never found two alike, so each one is special!

Wow, every snowflake that lands on your mitten began as a tiny speck of dust! High in a cold cloud, water vapor, which is water floating in the air as a gas, freezes onto that speck. The result is an ice crystal, and it grows bigger as more vapor sticks to it.

As it grows, the crystal builds itself with six sides. Why six? Tiny bits of water lock together in a six-sided pattern as they freeze.

Six sides are just the start, because every crystal grows its arms in its own way. Warmer or colder air and more or less moisture, or wetness in the air, change the shape, so some crystals look like flat stars and others like tiny columns. Each flake travels its own path through the sky, so no two look exactly alike.

Wilson Bentley, a farmer in Vermont, wanted to see those one-of-a-kind shapes up close. In 1885, he used a camera and a microscope to photograph a snowflake. Thanks to his pictures, we can see how a speck of dust in a cloud becomes a one-of-a-kind star.

Imagine you are a speck of dust floating high inside a freezing cloud. Around you floats water vapor, which is water as an invisible gas. Suddenly the vapor freezes onto you, layer by layer, and you become the heart of a snowflake! By the time it drifts to a December street, it will sparkle like a tiny Christmas ornament.

That ornament is an ice crystal, a frozen solid with flat sides, and it grows as vapor freezes onto its edges. It almost always has six sides or six arms, because water's tiny building blocks lock together that way when they freeze. Then the weather acts like an artist, because temperature and moisture, or wetness, decide how each arm grows. Some become flat plates, some skinny columns, and some feathery branches like frozen ferns.

Those feathery branches melt so fast that they were hard to study until a Vermont farmer got curious. In 1885, Wilson Bentley of Jericho, Vermont, attached a camera to a microscope, a tool that makes small things look big, and took one of the first photographs of a snowflake. He photographed more than 5,000 snowflakes and became known as "Snowflake Bentley."

Bentley's pictures showed something surprising: the snowflakes did not match. Because each crystal takes its own path through the sky, meeting its own cold and moisture, its shape comes out different. So the next flake on your mitten is a one-of-a-kind picture of its trip from a speck of dust.

It is a freezing January day in 1885 in Jericho, Vermont, and nineteen-year-old Wilson Bentley leans over a microscope hooked to a camera. On a tray sits one sparkling snowflake, and one warm breath could make it vanish! Could anyone photograph a snowflake up close before it melted? Almost no one had, but Bentley was determined to try.

That little star had traveled far before reaching Bentley's tray, and its story began high inside a cloud. There, water vapor, an invisible gas made of water, freezes onto a tiny speck of dust or pollen. That speck is the seed of a snowflake. More vapor keeps freezing onto it, and a crystal too small to see begins to grow.

Under Bentley's lens, those hidden crystals finally showed their secret: six sides, again and again. The reason lies in water itself, whose tiniest building blocks, called molecules, link together in a six-sided pattern. As the crystal grows, six arms sprout outward like spokes on a wheel. Because all six arms grow in the same bit of sky, they often look alike.

Not every snowflake grows lacy arms, though, and the weather inside the cloud is why. Temperature and moisture team up to shape each crystal as it grows. Around 5°F in very moist air, crystals tend to sprout fancy branching arms, while other temperatures build flat plates, thin needles, or hollow columns. A falling flake passes through changing air, so its shape can change on the way down.

Because every flake rides through different air, Bentley, who photographed thousands of crystals, said he never found two exactly alike. Even tiny changes along a flake's path alter how its arms grow. So when snow falls this December, catch a flake on your mitten. It began as vapor on a speck of dust, and it may be one of a kind.

Here is a puzzle for the next snowy December day: catch a falling snowflake on a dark mitten and count its points. You will almost always find six, not five or seven. These sparkling crystals decorate windows and wreaths all season, yet one is often smaller than a pencil eraser. What secret rule is hiding inside, and where does it begin?

The answer begins far above the rooftops, in a freezing cloud. There, water vapor, an invisible gas made of water, meets a speck of dust and freezes onto it. Can you imagine a snowflake starting as a bit of dust? It's true, and as the tiny crystal drifts downward, more vapor freezes onto it, building it bigger layer by layer.

As those layers pile up, the crystal shows off its secret rule: six sides. Water molecules, the tiny building blocks of water, lock together in a six-sided pattern as they freeze, like puzzle pieces that only fit one way. Temperature and moisture then decide the shape: very cold, damp air near 5°F tends to grow feathery, branching arms, while other weather builds flat plates or thin needles. All six arms feel the same weather at once, so they often grow like matching twins.

Those delicate patterns were hard to study for ages, until a young man in Vermont decided to look closer. In 1885, Wilson Bentley of Jericho, Vermont, attached a camera to a microscope and took one of the first photographs of a single snowflake. Since snowflakes melt fast, he worked in the cold and caught each one on a dark board. Over his lifetime he took about 5,000 photographs and became known as Snowflake Bentley.

Out of those 5,000 photographs, Bentley never found two snowflakes that matched exactly. The reason is the journey: each flake winds through the sky, meeting slightly different temperatures and moisture, and its arms record every change. With so many possible paths, scientists say it is extremely unlikely that two complex snowflakes would ever match exactly. So when snow sparkles on a Christmas wreath, remember that each flake began as vapor on a speck of dust, grew six arms, and traced a path across the sky that was all its own.

You may have heard that a snowflake is just a frozen raindrop, but that belief is wrong. Frozen raindrops are called sleet, and they bounce off the sidewalk like tiny pebbles. A snowflake is something far fancier: a lacy ice sculpture built in the sky, one arm at a time. Picture a delicate star so light that it lands on your mitten without a sound. No wonder people at Christmastime cut paper snowflakes to hang in their windows!

That sculpture begins high inside a cloud, where the air is crowded with water vapor, an invisible gas. When the vapor meets a speck of dust or pollen, it can freeze right onto it, skipping the liquid stage completely. Can you imagine a seed so small you could never spot it? That speck is often tinier than the period at the end of this sentence, yet it gives the first ice a place to cling. Soon a baby crystal takes shape, and it is already a tiny six-sided prism, like a microscopic hexagon.

That six-sided shape is no accident, because it is written into water itself. As water molecules freeze, they lock together in a hexagonal pattern, like dancers who can only join hands in rings of six. As the crystal tumbles down through the cloud, temperature and moisture act like invisible sculptors. Around 5°F, with plenty of moisture, the arms sprout feathery branches, while other conditions build flat plates or slender columns. Since all six arms ride through the same air at the same moment, they often grow into nearly matching patterns.

Those matching patterns caught the eye of Wilson Bentley, a farmer from Jericho, Vermont, who wanted to see what snowflakes really looked like up close. In 1885, when he was about 19, he attached a camera to a microscope and is credited as the first person to photograph a single snow crystal. It was tricky work, because he had to catch flakes on a cold, dark tray and snap the picture before they melted. Over his lifetime he photographed thousands of crystals, and none of them matched. People came to call him "Snowflake Bentley," a nickname that still lives on today.

Snowflake Bentley never found a twin because every crystal takes its own winding trip through the sky, meeting slightly different air along the way. With so many possible paths, a perfect match is nearly impossible. Snow crystals still matter today, because scientists study how they grow to better understand clouds and weather. Mountain snow also works like a frozen reservoir, melting in spring to feed rivers that supply water to farms and cities. So when flakes drift past your window this December, remember that each began as a speck of dust and carries a record of its own journey through the sky.

Picture a number with eighteen zeros: that is about how many water molecules physicist Kenneth Libbrecht estimates are packed into a single snowflake. Yet the whole thing is small enough to perch on the tip of your mitten, a sparkling six-pointed star glittering under the porch light. Each one drifts down in silence, turning December streets into living holiday cards and inspiring the paper snowflakes taped to windows. How does a plain gray cloud build such delicate jewelry, and why does it almost always have six sides?

The answer begins high in a freezing cloud, where invisible water vapor drifts around a speck of dust or pollen. When the air is cold enough, the vapor settles on that speck and freezes into a tiny ice crystal, much as frost creeps across a window. The speck is only the starting point, since more vapor keeps freezing onto the crystal as it drifts. Once heavy enough, it falls, and in air near freezing, crystals may clump into big, fluffy flakes. Whether a flake is one crystal or a crowd, a single crystal almost always has the same number of arms: six.

That six is no coincidence, and the reason is hidden inside the water itself. Each water molecule is made of one oxygen atom and two hydrogen atoms, and as water freezes, those molecules lock together in a repeating pattern of six-sided rings. The crystal grows outward by adding molecules to that pattern, so its outline echoes the hexagon built into the ice. In other words, a snowflake is a hidden blueprint enlarged until your eyes can finally see it.

But if every flake follows the same six-sided blueprint, why don't they all look alike? The secret is weather: as a crystal tumbles through the cloud, the temperature and the amount of moisture in the air change how it grows. At about 5°F (-15°C) with plenty of moisture, crystals tend to sprout feathery, branching arms called dendrites, while other conditions build flat plates or slender columns. Here is the clever part: all six arms of one crystal ride through the same air at the same moment, so they often grow into nearly matching patterns. A snowflake is therefore a tiny record of the journey it took, written in ice.

That written-in-ice record is exactly what a Vermont farmer named Wilson Bentley wanted to capture. In 1885, in the town of Jericho, he attached a camera to a microscope and photographed a snowflake, a feat that took great patience. He caught flakes on black velvet, lifted them with a feather, and worked fast in the freezing air before they melted. Over his lifetime he made more than 5,000 photographs, and neighbors began calling him "Snowflake Bentley." His pictures let people study the delicate shapes in detail, and scientists and artists still admire them.

Bentley noticed something in all those pictures: he never found two flakes that matched. That makes sense, because each crystal follows its own winding path through the sky, meeting slightly different air at every moment. With about a quintillion molecules to arrange, the number of possible designs is so huge that two complex snowflakes matching exactly is extremely unlikely. Very simple crystals, such as tiny plain hexagons, could look alike, but the fancy ones almost certainly do not. So when a flake lands on your glove, you are looking at a quintillion molecules arranged in a pattern that the sky may never make again.

In January 1885, a 19-year-old farmer named Wilson Bentley stood in the Vermont cold, hardly daring to breathe, and made history with a single snowflake. He had tried sketching snowflakes, but they melted or blew apart before he could finish a line, so he tried something new: a camera attached to a microscope. The photograph showed a delicate six-armed star, sharp against a dark background, and it is widely recognized as the first photograph of a single snowflake. How can something so intricate drift out of a plain gray cloud? The answer combines dust, invisible vapor, and some surprising geometry.

Start with that gray cloud, because the story of every snowflake begins there, and its first character is far less glamorous than a star: a speck of dust. High in the sky, water vapor, which is water in its invisible gas form, drifts among tiny particles of dust, pollen, and other debris. When the air is cold enough, vapor molecules settle on one of those specks and lock into place as ice, skipping the liquid stage entirely in a change scientists call deposition. Scientists call the speck a nucleus, and it works a bit like the seed of a plant, giving the crystal a place to start. The crystals that finally fall are often just a few millimeters across, smaller than a pencil eraser, yet each one is built from an enormous number of water molecules stacked in perfect order.

Once that first bit of ice exists, it quickly takes a shape, and the shape is almost always built on six sides. The reason is hidden inside ice itself: water molecules link together in a repeating hexagonal arrangement, with angles of about 120 degrees. As more molecules attach, they follow that pattern, so the crystal's outer form echoes its molecular structure, like a mosaic whose big picture is decided by the shape of its tiles. Notice the distinction, though: not every snow crystal is a star, since some grow as slender columns or needles, but even those are six-sided prisms. So when you look at a snowflake, you are seeing a pattern far too small to see, enlarged by nature until it fits on your mitten.

Six sides are only the starting point, because the weather inside the cloud decides what happens next. In the 1930s, Japanese physicist Ukichiro Nakaya grew snow crystals in his laboratory on the island of Hokkaido and showed that their shapes depend on both temperature and moisture. Around 23°F, crystals tend to grow as needles and columns, while near 5°F they sprout the branching, fernlike arms most people picture, and wetter air produces more elaborate branches. Because a falling crystal passes through changing layers of air, its shape can shift along the way, and its six arms all meet the same conditions at about the same moment. That shared experience, not any secret communication between the arms, explains why the branches of a snowflake so often look like twins. Nakaya is often quoted as calling snow crystals letters sent from heaven, and the phrase fits, since each one records the journey that shaped it.

Nakaya worked in a laboratory, but Bentley worked the old-fashioned way: outdoors in the Vermont winter, one flake at a time. Living on a farm in Jericho, he caught flakes on a cold black tray, moved them with a feather, and photographed them before they could melt. Some neighbors thought his hobby was odd, but over the decades he photographed thousands of crystals, and in 1931 a book called Snow Crystals shared about 2,300 of his images with the world. He died that December, not long after the book appeared, and today he is remembered fondly as Snowflake Bentley. From all those photographs he drew a bold conclusion: no two snowflakes are alike.

That bold claim is still argued over today, and the argument shows how evidence and definitions can pull in different directions. Bentley's evidence was impressive, yet thousands of photographs are a tiny sample of the countless flakes that fall each winter, so his observation could not prove the claim. In 1988, atmospheric scientist Nancy Knight reported two ice crystals that looked identical under a microscope, though both were simple in form and would still differ in tiny molecular details. So the answer depends on the word alike: complex, branching flakes are almost certain never to repeat, while simple ones might occasionally match. That is why the paper snowflakes taped to windows every December are truest to nature when they are cut with six points instead of eight. And it means the flake landing on your sleeve is a small record of its own path through the sky, a letter, as Nakaya might say, written only once.