Friday, March 7, 2008

Co-op Week Seven {Clouds}

 How do clouds form?  They are made up of masses of water droplets or ice crystals suspended in the air.  Warm moist air rises and expands, and as it rises through the atmosphere it also cools (about 5*F every 1000 feet).  When it rises to a point where the water vapor begins to condense, a cloud forms.  The temperature at which the water vapor condenses is called the dewpoint,  The first thing we did in class, after discussing this, was a little experiment to see if we could figure out the approximate dewpoint in our classroom.  I don't have pictures, but will describe it. 

Use a clean soup can and fill about halfway with slightly warm water.  It just needs to be lukewarm (or at least a little warmer than the room you are in).  Put an outdoor thermometer in the can and get a temperature reading of the water.  Ours was around 60* I think.  Then add crushed ice or small ice cubes to the water, a bit at a time, and stir.  Watch the outside of the can for condensation - in the form of tiny water droplets, or more likely, a bit of "fog"  Once I explained to the kids that they were watching for a fog on the can kind of like when they breathe on a mirror, then they understood!  They were to record the temperature of the water when they first noticed the condensation on the outside of the can, and that should be the approximate dewpoint of the room - the temperature at which the air could no longer "hold on" to its water vapor and had to "set some of it down" on the cool surface.  We had two groups working on this project, and they both concluded the same temperature (whew!!!!!) of about 40*F as the dewpoint.

So... back to the clouds... Clouds can also form when cold and warm fronts meet - the same thing happens, the warmer air cools and the water vapor starts to condense.  Then we did a demonstration to see clouds forming.  I had a large plastic jar with some hot water in it, and set a strainer with ice cubes in the opening.  As the warm moist air rose, it was cooled by the ice and there was a little bit of water vapor condensing.  This was REALLY hard to see in the picture!!!!  I took this picture when we tried it at home, and in the mini-screen on my camera it showed up great - but the little wisp of cloud seems to have disappeared in the process of uploading the picture to my computer.  Trust me, it was there.

 Then we talked about the different types of clouds and how they are classified.  I tried to keep it simple, and since I had several books with good pictures, we took some time to look at those to get a better idea of how to identify a cloud.  You can see a brief overview of cloud types here  (that is a great website, by the way - if you need some info for a weather unit - good pictures and concise explanations.  And not biased with global warming nonsense either.

The kids each got a copy of the "Cloud Detective" page from Considering God's Creation and they are supposed to take notes on the clouds they observe on two days this week.

And wonder of wonders, we had more time than we needed in this week's class!!  We just looked at the pictures in my weather books for the last several minutes because I was out of teaching material.  First time that has happened this co-op.  I thought the dewpoint experiment would take quite a bit longer.


SuzyScribbles said...

Oh, that is so neat about your Grandma's flour sack aprons! Can't wait for your show and tell so I can see the quilt. Maybe I misread your comment (I read it pretty fast and you know how tricky it is to go BACK to read it again), but is your grandma's quilt made from flour sacks or just her aprons? You don't have to answer, but I was curious. Guess I can find out when I read your future S&t.

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