The clean snow experiment

Here's a fun, easy and educational experiment to do with the abundance of white stuff we have outside.  Find out how clean snow is.

My kids and I came up with this idea last winter when we took a walk on a snowy day.  My oldest daughter, Victoria, was scooping up handfuls of snow to eat.  When I made a half-joking comment about eating pollution she assured me it was fine because she was only eating "clean snow."

I told her about how some groups like the Canadian Food Safety Institute has warned against eating snow because it is “a potential source of heavy metals, toxins, bacteria and viruses,” particularly in urban areas.  Scientists also talk about how snow literally cleans the pollutants from the air (by forming around them and thereby being full of them) on sites like this one, which still reassures parents that snow in rural areas is pretty safe.

I felt a science experiment coming on!  We decided to see if we could find any pollutants.

Victoria scooped up a jar of “clean” snow and filled another jar with tap water. She microwaved the snow to melt it and we all took a look.

Hmmmm….

It looked pretty dirty!

Then I got a coffee filter and she helped pour the melted snow through it to see what sorts of things it would trap.

There was quite a lot of dirt, some things we couldn’t identify, and something Victoria guessed was a bug’s leg. I think it’s more likely a very tiny animal hair, but it’s still not something you might want to munch!  (You can see our results in the slide show.)

Victoria was annoyed but proclaimed that she was still going to eat snow sometimes.  She knows about the hygiene hypothesis and I told her that was fine with me.  I had already done research and had concluded on my own years back that I felt pretty safe with my kids eating our rural Minnesota snow.  (See the links below to research it on your own with your kids.)

Here's some extensions for further experiments:

• Compare melted snow from two different locations, like from near a highway and from a wooded area.
• Put a jar outside to catch snow as it's falling and scoop up snow on the ground in another jar.  Melt the snow in each and compare them.
• Look at melted snow under a microscope.
• Melt and strain some relatively clean, fresh snow and put it in a glass.  Fill another glass with tap water and another with bottled water.  Label them a, b and c.  Can the kids tell which is which?  Which tastes best?

Further reading:

The National Snow and Ice Data Center has tons of great information about snow and they say it’s safe to eat except in very polluted urban areas (they say lots more, too, this would be a great page for a unit study on snow!).

And BYU’s Newsnet says it’s a myth that you can’t eat snow, except in very polluted areas.