Why is snow soft and ice hard?

Answered by Alex DeSmet, Meteorologist, National Weather Service, Pocatello

This is a good question, because snow and ice are both water in a frozen form. So, why do they feel so much different to us? Well, the answer is actually fairly simple, and it has to do with air. As snowflakes fall to the ground and begin to pile up, air is trapped in the empty spaces between snowflakes. You could re-create this by placing some decorative Snowsnowflakes in a clear container and shine a flashlight through it. You should be able to see some light passing through the airspace in between the snowflakes. In this first picture (below), we can see the fresh snow on the left. Notice the white space in between the snowflakes inside the black circle. This white space shows the air trapped in between the snow crystals. Now, as snow stays on the ground for a few days, the air space between the snowflakes slowly goes away. Eventually, almost all of
the air trapped in this old snow would go away, leaving ice. This is what we call a glacier. Glaciers usually take years to form. You can re-create this by making a snowball out of fresh snow. If you continue to squeeze the snowball in your hands, you will squeeze much of the air in between the snowflakes out, creating a hard, mostly icy snowball.

Here’s what this would look like under a microscope:Snow2Notice the nearly perfectly shaped snowflake on the left. This is the fresh snow. But after the snow has been on the ground for a few days, that air gets squeezed out, and the old snow doesn’t even look like a snowflake anymore. If you looked at your hard snowball under a microscope, it would look a lot like this.

Now let’s look at this close-up of an ice cube. Notice there is almost no air inside of the ice and it looks solid. So, this is why ice feels hard.Snow3

Did you know? You can make ice cream out of snow! You or your parents can search the internet for the many recipes that are there. Using clean snow and a couple of other ingredients, you can make ice cream! 

 

 

 

Is Snow Clean?
A snowflake begins to form when an extremely cold water droplet freezes onto a pollen or dust particle in the sky. This creates an ice crystal. Gradually, ice crystals attract more water molecules. Once they are heavy enough, they begin to fall. As they fall, more water molecules are attracted to the primary ice crystal. These additional water molecules attach to the ice crystal and increase its size.

Snow4

As snowflakes fall through the sky , their intricate latticework form a sort of net for catching pollutants that may be in the atmosphere. So, snow really isn’t as clean as it looks.

Materials: a cup for scooping, two identical glasses, two coffee filters

  1. Scoop a cup of snow and put it into a clear glass. Let it melt.
  2. In the second glass, pour a cup of water.
  3. Compare the water in the two cups. Which looks cleaner?
  4. Try filtering each cup of water through the coffee filter. What is left behind? A magnifying glass can give you a closer look.

There will be dirt collecting on the melted snow filter because every snowflake forms on a speck of dust or salt. As the snowflakes fall, they collect more dirt from the air.

According to snow research done at Brigham Young University, snow is safe to eat as long as it is fresh. 

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