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Birth of a snowflake 2

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Birth of a snowflake 2

  1. 1. Birth of a SnowflakeHow they are formed
  2. 2. This assignment has been developed to instruct youon the use of sound within a PowerPoint presentation.Therefore, narrating a report written by someone elsedoes not give you the right to take credit for itscontent.  Instructions:  Choose your weather topic  Type the report into a PowerPoint presentation  Select the slide you wish to record  Click on the slide show tab and begin recording your reading  Be sure to check your timing and your work before submitting to my wiki  Add at least two pictures or clip art to your presentation  Comment on other classmates presentations Remember to only add comments or suggestions that are constructive and ethical in nature
  3. 3. How snowflakes are formedA report by Sam MontanaNarrated by Kay Cremeans
  4. 4. Precipitation comes in many forms such as rain, sleet,hail and snow. A snowflake starts out as a dustparticle. Then water vapor starts to condense ontothe dust particle and if the temperature is coldenough it freezes. Most naturally occurring ice isshaped in a hexagonal structure. The snowflakebecomes more and more formed because watermolecules have an attraction for each other and wateris more stable in the form of ice. The water moleculeis even more stable in the form of ice when arrangedin hexagonal layers, and that gives the snowflake a6-sided symmetry. As more and more water vaporcondenses onto this ice crystal, the snowflake grows.
  5. 5. Several factors influence the shape of any onesnowflake, the temperature, humidity and the aircurrents. If there are a lot of dust and dirtparticles mixed in during this freezing process, theshape of the snowflake is affected. As these icecrystals move up and down in the cloud with theupdrafts and downdrafts they continue to formand be shaped. Finally the snowflake is heavyenough to escape the clouds updrafts and falls tothe ground.Falling to the ground can also alter its shape. Ifthe snowflake spins it will probably keep itssymmetrical shape. If they aren’t spinning whenthey hit the ground they will lose their shape andbe lumpy.
  6. 6. Common snowflake shapesThe shape of the ice crystals that form the snowflake isdependent on temperature. Here is a list of their shapes andthe temperature that they formed in.25 – 32 F: Thin 6-sided hexagonal crystals, formed in the highclouds.21 – 25 F: Needles or flat-sided crystals are formed in themiddle height clouds.14 – 21 F: Hollow columns10 – 14 F: Sector plates, which are hexagons withindentations.3 – 10 F: Dendrites, lacy hexagonal shapes.Snowflakes are composed of many ice crystals that affect theirshapes. They might start out as a one shape and land asanother shape. You will probably never see two snowflakes thatlook alike, it is a constant though that in the formation of one,it is always 6-sided, or hexagonal.Highly magnified hexagonal dendrite snowflake
  7. 7. Why is snow white?Water is clear, so why is snow white. Theanswer has to do with the fact thatsnowflakes have so many light-reflectingsurfaces that they scatter the light into all ofits colors, so snow appears white. It has todo with how the brain perceives the lightinto the color.
  8. 8. There is another form of snow that somepeople have never heard of or seen, it is calledgraupel, also referred to as snow pellets. Somedescribe it as soft fuzzy hail. It starts out as asnowflake and then combine with super cooledwater droplets frozen together. These are smallpellets, not large like hail might be and soft.
  9. 9. A side note about updrafts and downdraftsA snowflake can go up and down in a cloudgathering more crystals that form its shape until itgets heavy enough to fall to the ground. You canactually see this updraft and downdraft actionyourself when it hails. The next time it hails and ifthe hail is big enough, look for ones that havebroken in half on the ground. You can see ringsinside the hailstone. Each ring represents a trip upand down in the cloud. The hailstone rises andgathers another layer of ice, then it falls in thedowndraft and melts a little bit, rises up again andrefreezes picking up another layer of ice until it getsheavy enough to fall to earth. To learn about hail,you can read All About Hailstorms and How HailForms.
  10. 10. Once you have reviewed the previousreport, you are to search the internet for asimilar story and develop a narrativepresentation.Once you are finished with yourpresentation submit it to my wiki for reviewby your classmates.http://student-assistance.wikispaces.comPlace your finished assignment andcomments on the PowerPointnarrations page
  11. 11. ReferencesMontana, Sam (2008). How snowflakes are formed. Retrieved March 26, 2012 fromhttp://weather-meteorology.knoji.com/how-snowflakes-are-formed/

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