"What will happen when you mix cold water with warm water?" This was the investigative question that the first graders explored in their weather lab this week. The investigation started with the students watching a beaker of boiling water. OK, we all know that "a watched pot never boils", but this time there were colored dots of paper in the water and the students observed an up and down, or circular motion happening in the water. Then the students observed a glass fishbowl with room temperature water in it. A blue ice cube was gently placed in the bowl and the students observed several things. First, the ice cube floated. Second, they noticed that as the ice cube melted blue-colored water sank to the bottom of the bowl and formed a blue layer across the bottom. Using the SmartBoard, we looked at how water molecules pack closely and tightly together when they are cold, and that this makes them more dense.
Next, some hot, red-colored water was gently poured into the bowl. Immediately, the students noticed the red water tried to go down but was pushed right back to the top. Here it formed a distinct layer across the top of the bowl. Using the SmartBoard once again, the water molecules were spread out, so students could see that they were farther apart and that made them less dense or lighter. Now the students could see 3 distinct layers in the fishbowl, a cold, blue bottom layer; a clear, room-temperature layer; and a warm, red layer across the top.
We spent several minutes discussing the observations, and then decided to try someting else to help answer the question. Now students took a cut-off 2 liter bottle filled with chilled water, and a baby food jar filled with warm, red water and placed the baby food jar into the container of cold water. The students poked two holes in the aluminum foil cover on the small jar while it was inside the big container. What do you think happened? Ask your first grader to explain what they saw happening and what "convection" is.
(Mrs. Friedlander's class and Mrs. Oemichen's class will be doing this next week.)
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