Backyard Biology

Nature stories from my backyard and beyond

Nature Activities

Catching Snowflakes

Thursday, February 3, 2011

A favorite wintertime activity for many children is maing paper snowflakes. Fold the paper just right, make a few cuts and you have a perfect six-sided snowflake. I wonder how many of us who have made a paper snowflake have ever taken a really close look at a snowflake. Probably very few. However, seeing the beauty of a real snowflake is much easier than making a paper one. All that is needed is a piece of black material, a magnifying glass and a snowy day.
By looking closely at real snowflakes, you will quickly realize that not all snowflakes are six-sided. The international Commission on Snow and Ice defined seven different patterns of snowflakes: star, plate, needle, column, column with a cat at each end, spacial dendrite and irregular. Other snow scientists recognized that not all snowflakes seemed to fall withn this pattern of 7 types, so they came up with their own classification system. You can check out some of these patterns at SnowCrystals.com web site at
http://www.its.caltech.edu/~atomic/snowcrystals/class/class.htm.

The pattern that a snowflake grows into depends a lot on the atmospheric conditions under which it was formed - particularly the temperature and humidity. To learn more about how a snowflake grows and why, check out the Snowflake Primer at
http://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htm.

No matter in what conditions the snowflake grows, catching them and observing them up close is a rewarding experience. And if you like to keep notes, why not make up your own classification system for the snowflakes you collect? As well as identifying different patterns of snowflakes, you might want to keep a record of the temperature and humidity that they were collected under. Perhaps you will notice a pattern of certain types of flakes forming under specific conditions.
snowflake 3snowflake 4

 

snowflake 5snowflake 2








Materials
:

  • a piece of black velvet (actually any piece of dark material will work. For the pictures below, I used my black fleece hat)
  • magnifying glass (the higher the magnification the better - a jewelers loupe of about 20 power is ideal)

Instructions:

  1. Leave the velvet outside in a garage or other area not exposed to the snow for 15 to 20 minutes to let it cool to the outside temperature. If you don’t have a garage, you could leave the hat in a car, or cover it with a piece of wood, plastic container or any other handy object.

  2. After the velvet has cooled to the outside temperature, hold it in the snow for a few seconds, then pull it back into the garage, car or wherever you are standing that no more snow will fall on it. The trick is to get a good collection of snowflakes to look at but not so many that they overlap each other.

  3. Look at the snowflakes with the magnifying glass. You will be able to clearly see the many different shapes of snowflakes you collect.

    caution: Do not breath on the snowflake. Your warm breath will melt it! As long as the velvet stays cold, the snowflake will last for quite a while, giving you ample time to look at it.

Using a magnifying glass or jewelers loupe:
Hold the magnifying glass about 1 inch from your eye. Lookig through the magnifying glass, move the object you are looking at towards you until it is in focus.

Alternative magnifying glass:
If you do not have a magnifying glass, try using a pair of binoculars. Look through them backwards and move the object towards the eyepiece until it is in focus. It will have to be quite close to the eyepiece.

 

Measuring humidity

Measuring the humidity of the air is easy with a wet-bulb thermometer or sling psychrometer.

Materials:

  • two identical thermometers
  • piece of gauze
  • string
  • Wet-bulb thermometer chart

Instructions:

  1. Tape the two thermometers together back to back. Attach a string to the top of the thermometers
  2. Wrap a piece of gauze around the bulb of one of the thermometers.
  3. Wet the gauzethermometer
  4. Use the string to whirl the thermometers over your head.

    As the thermometers are whirling through the air, the water on the gauze will evaporate. This will cause the gause to cool and bring the temperature of the thermometer down lower than the air temperature. The thermometer with the gauze (the wet bulb) will read a lower temperature than the other (dry bulb) thermometer.

  5. Calculate the difference between the two thermometers.
  6. Locate the temperature of the dry bulb thermometer on the chart. Move across the chart the difference between the two thermometers. That will give you the relative humidity by percent. For instance, if the dry bulb temperature is 10 degrees F and the difference between the two is 2 degrees, then the relative humidity is 56%.

wet bulb chart