Friday, November 29, 2013

Teaching The Scientific/Experimental Method: Part III: Water Cycle

Just as a seed has a life cycle (whose growth is dependent upon many variables), the children understand that water has a life cycle as well.   Again, we started with what we knew and began to ask questions.  Tapping into their background knowledge, a good number of children already understood the water cycle as a natural process.  They depicted the continuous movement of water back and forth, between the earth and the sky, and many used arrows to show the pathways that water takes:

R. envisions the movement up and down from the earth into the clouds
I:  When the rain falls, then it goes into an ocean or a river. Tiny little rain drops go into clouds.
M. sees the cycle as a before/after process that involves time...and things unseen
Some already knew the word "evaporation" and were able to share their understanding of what it meant to the group

(left):  E.K. created an informational brochure to explain what she knew about the subject, introduced by Mother Earth herself, carrying a pocketbook. Earth explains:  "It comes down, it goes up again.  it goes down and it goes up and down and up..."  E.K. shared with the class that the reason this happens is gravity - "it makes the rain come down." 

What most children were curious about was how the process worked. 

T:  What brings [the water] up?  Maybe wind casts it up.  I do not know. 
P:  I want to know how does it get back up into the clouds?
R:  The water gets into the clouds before it rains.
G:  How does air pick up water?

Below:  G. imagines the water droplets going up into the sky - they are grasping rescue lines from an invisible passing airplane who will take them to the clouds. 

Above: W:  One day I left a cup of water outside.  Then the next morning, it was gone.  I don't know how it did it.  I couldn't figure it out. 

As we were conducting our plant experiments, we noticed that as we waited for our seedlings to sprout in the sun for Test #4, something strange was happening inside the growing kit:  water droplets were forming on the top of the plastic cover (see the previous blog post:  you can see the condensation on the top of the kit in the picture for Test 4).  We brought this to the attention of the group and asked them to postulate their theories about what they thought might be happening:

Why is there water on the top of the growing kit?
T:  It think it is water vapor.  It could be dew.  This stuff gets on plants sometimes.
N.B.:  Condensation.  Evaporated water gets stuck on the walls.
W:  It's all over my window every morning. 
N.B.:  The water we put in there evaporated up.
E.K.:  You can see it sometimes when you breathe on the wall.
N.S.:  [The kit in the sun] got too warm.  [The water] turned into steam and floated up, then got stuck there [on the lid].
M:  Warm water from the shower turns into steam.  It also happens in places outdoors.
A.C.:  I sometimes see mist over the river.
L:  That's fog.  Is that different?
I:  I know what fog is.  It's clouds that are really close to the ground.  The steam thing...when it gets really hot, water goes up into the clouds, then it gets too heavy and it falls.

To try to figure out how water might go up (just as it had in the growing kit), several ideas for tests were proposed.  As a group, we decided to try testing water in the microwave.  Sensing that temperature might have a part to play, the children wanted to know what would happen if the water was heated up.  We wanted to know how the water (and its volume) changed over time. 

Using small glass bottles, filling them with water and then measuring that amount in a graduated cylinder, we determined that we would start our tests with with 50 ml of water.  We would heat the water in the microwave on the high setting.  Group One would make predictions and record results at 10 seconds, 30 seconds, 1 minute, and 5 minutes.  Group Two would make predictions and record results at 1 minute and 5 minutes.  After each test in the microwave, the groups would stop to see a) how hot the water had gotten, b) pour the water into a graduated cylinder to see how much water was still left in the bottle, and c) discuss and record their observations. 

When each group had completed their testing, we regrouped to compare notes and discuss our observations. 

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