Friday, January 27, 2012

Maybe I'm looking on the bright side of things, but I like how it's working out that we keep running out of time and have to finish up an experiment the next day. I think it's a helpful way to reinforce learning for many students, so I'll just pretend I planned for it to happen that way.

Thursday morning we revisited the applesauce experiment. Many kids had written conclusions that didn't show a deep consideration of the data collected, so together we talked through the idea that in a known solution (sugar water) no particles were captured at any level of straining. If applesauce particles were captured, then it must not be a solution. This kind of logical reasoning is not natural for all students, and I'm glad we took the time to review what we had observed. I introduced the concept of suspensions and then kids shared their questions.

I have been VERY pleased at the types of questions they have been coming up with. Having taught third and fourth grade for the past five years, it is inspiring to see how in this arena, their questions show the growth in thinking you'd expect between the two age groups. Also, as I've said before, the more good questions we collect, the easier it will be for students to select one and design an independent experiment in a few weeks.

Next I posed a new question: do solutions freeze at the same rate as a pure substance?
Writing a hypothesis is serious work.

Working together we created a series of four apple juice dilutions -- from 1/2 juice and water to 1/16 juice and the rest water. We also set up a cup of straight apple juice and straight water. Then we poured the rest of the juice into 16 cups and stuck sticks in them for an afternoon snack.

I love this picture, taken by a student. The colors really show the juice dilutions.

In the afternoon during math, Su put the tray of juice cups in the freezer. They had been chilling for an hour or so, so that they were all the same temperature when they went into the freezer. Then we had a wacky afternoon where we went trucking down to the kitchen at half hour intervals, each time walking through the gym where classes were going on. ("Walk on the red line; do not interrupt the game the kids are playing.") Each time I pulled the tray of juice cups out of the freezer, we'd look at each one and kids would record observations about their appearances. By the third visit, the pattern was clear: the straight water was the most frozen and the straight apple juice was still slushy. The juice pops weren't frozen so we had those at snack on Friday morning. Friday afternoon we revisited the data and concluded that pure substances freeze faster than solutions. Practically life application: salt on roadways in the winter create a salt/water solution that prevents the moisture on the roads from freezing up.

A big thank you to Emily in the gym and the ladies in the kitchen. I was less organized than I like to be this week, and hadn't warned any of them that we'd be trooping through the gym Thursday afternoon or descending on the kitchen as they were trying to finish their post-lunch clean up. I am constantly grateful for the flexible and kind people I work with.

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