Friday, November 29, 2013

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

And so our microwave tests began… 

 
First, the children made their predictions:  what do you think will happen at each of the timed intervals?  What do you think will happen at the end of our tests - will the amount of water stay the same, change, or will the water disappear altogether?  We took each of our groups out into the hallway to use the microwave that hitherto had only been used to heat up lunches, coffee, and tea. It would now be transformed into a scientific tool to advance our knowledge of the process of evaporation. 

Clipboards and pencils in hand, the children brought their predictions with them and waited to record their observations.  At the end of each of the timed intervals, the children looked at the bottle of water to see if there were any visual changes and they were allowed to briefly touch the bottle to feel if it felt warm or hot.  We then poured the water out of the bottle and into a graduated cylinder to see if any water had been lost. 

After the children recorded their findings, the water was then poured back into the glass bottle and placed back into the microwave for the next round of timed tests. 
 
After each group conducted its testing, together we shared our findings.
(Above and below): on the left:  predictions/ on the right:  observations/results of our tests
 
 
What was our original question?
A.L.:  Does water evaporate when it is heated up in the microwave?
What were our predictions?
E.S.:  It will turn into smoke or steam and it will be hot. 
A.L.:  Prediction:  After one minute, there will be no evaporation and it will be hot.
L:  It will evaporate up.
To where?
L:  To the top of the microwave. 
I:  It thought it would be boiling hot.  I thought it wasn't going to evaporate but [that] it would boil. 
A.L.:  On my prediction, it said, "No evaporation" and "it will be hot."
"Watch out!"  It's hot!

 
J:  I thought a little water would escape and evaporate.
Once we had our question and made our predictions, what was our next step?
P:  We had to do our test.   We measured by milliliters. 
M:  We measured out 50 milliliters.
When we are doing tests, we want each group to start with the same amount of water so that we can compare data.  Did we use anything else to help us measure?
A.L.:  The amount of minutes that we used [with the microwave]! 
Time!  Yes, time is a unit of measurement.  So we were using time to conduct our tests. Now that we have talked about what we were measuring and how we were measuring it, we can talk about our results.
P:  I know why [the water] was all gone, because the more longer [sic] we left it in the microwave, the hotter it got and then more of it was gone.  At the last one, I looked in and I saw bubbling water and it looked really hot. 
 

So with an increase in time and temperature, the amount of water decreased.
Did Group One notice that there was something inside the microwave?
T:  We didn’t see any tiny bubbles.
P:  When we took it out we saw some mist on the top.
 
Okay, Group Two, let’s talk about our results. 
 
C:  A minute one,  it got really hot, we measured it in that cup.
I:  1 ml escaped.  We had 49 left.
So Group One lost 5 ml of water at one minute but Group Two lost only 1 ml.  Why is that?
A.C.:  I know why, because we [Group One] used the microwave more.  So for ten seconds, that’s why nothing was up.  And since that was your first [trial], it wasn’t hot so nothing went up.
J:  We didn’t do it for 10 seconds, and 30 seconds...If we had it would have been the same.  Group 1, it was more hot since they had already done it twice, so more evaporated [by the end of their testing].
What happened at five minutes?
 

 
E.S.:  When we put it in the microwave and we took it out, we had lost 10 ml.
Now that we have shared our results, what might our next steps be? 
A.L.:  It could be double-checking your results.
A.C.:  If you are like a real scientist, like with chemists, you would have to clean up.
J:  Do another question…
What was the answer to our question?
Class:  Yes, water does evaporate! 
 
What did we discover with Group Two?
J:  That the top, the ceiling of the microwave was wet [they noticed the condensation].
I:  I had a different [idea], that half of it went to heaven and half of it would go to the ceiling [of the microwave].
When I open the door to the microwave what happens to the moisture at the top?
T:  It would get cold and it would disappear.
E.S.:  You open the microwave and all the air gets out.  But when you shut the door there is some [moisture] left in there...

Even though both groups had been given different time trials, they were able to compare their results and understand why there had been differences, and together they agreed that time and prolonged exposure to heat had facilitated the process of evaporation/condensation.  Both groups recorded a loss of water over time (evaporation) and both noted that the top of the microwave was wet (condensation).  Other questions about water still remained...

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