Wednesday, June 5, 2013

Testing Water Flow, Making Topographical Maps, and Experimenting with Buoyancy

May was another super month for continuing our water exploration.

We spent quite a few lessons testing the way water flows across and down different types of natural and man-made surfaces. It was fantastic watching the students make predictions about how water would flow along distinct geographical features that they selected around the school grounds. The students experimented by pouring water down asphalt inclines, grassy hills, ramps of small stones and large rocks, and over soil slopes. All this preliminary testing provided the students with a strong foundation on which to build their art installation at deCordova Sculpture Park in late May (More on that STEAM project!)

Since students were very interested in explaining the way mountains and valley's influence the flow of water I decided that we would use playdough to mold our own mini mountains and make individual topographical (topo) maps from them. Students found that topo maps are a great way to convey information about geographical features of a landscape and to visualize how water collects or flows around these physical elements. We discussed what these types of maps are especially useful for and students decided that topo maps are good for finding your way along "hiking trails" or while "canoeing and kayaking" and also for engineers who build roads and train tracks.

After molding their mini-mountains, the students measured the height and made slices through mountains at specific intervals. They then traced the outline of each layer of their cut mountain on a piece of paper - making rings that represented separate contour lines. (For details on how to do this lesson.)

Last month we also began exploring the physics of buoyancy. We started by defining density and buoyancy. To visualize density we talked about a cup of jelly beans and a cup of marshmallows and asked students to predict what would happen if they put each cup into the microwave. "They would melt!" responded the class. Yes, but the melted sugar and water from the jelly beans would almost fill the cup while the melted marshmallows would only fill the cup a little. Because the marshmallows are mostly air, they are less dense than the jelly beans. Next we discussed whether a jelly bean or marshmallow would be able to float in water. For those who enjoy hot chocolate with marshmallows in the winter time this was an easy question. We decided that for an object to be able to float it has to be "lighter" or have less density than the water...unless it is attached to something that helps it float, like a life jacket.

Next I asked if we could make a piece of clay float. I rolled a small piece of clay into a solid ball and asked the students to predict what would happen to the clay if we placed it in a tub of water. With contradictory responses, "It will sink." "It will float then sink.", "It will float." we decided to test it. After it sank, I gave each student a small square piece of plasticine modeling clay and asked them to try and make their clay float. Each student began to mold their piece into various shapes. They made cups, bowls, canoes, row boats, rafts, and even people. We had many "failures" before one student successfully produced a "boat". It was interesting that the students themselves came to define the clay as a boat only after they managed to make it float. Many students attempted to recreate the successful model but others kept to their original molds. At the end of class the students had decided that "No holes can be in the boat.", "Taller sides help it float.", "Make the clay thin.", "Keep the boat dry inside." and to "Put the boat into the tub carefully." They enjoyed the lesson so much so that we decided to continue with boats over the following Science Friday!

During the second session we began drawing comparisons by testing the buoyancy of clay boats to other objects. We compared wax paper, aluminum foil, and plastic weigh boats (of differing sizes) to the students' newly made clay molds. Students began by making predictions about which would have better buoyancy. After seeing the plastic float they wanted to test how much weight each of the boats could hold. Students used penny's to add weight to the clay and to the plastic boats and we were surprised to see that a few of the clay boats could hold just as much as the plastic boats.

Some students moved on to investigate whether they could make a piece of aluminum foil float. Using equal size pieces, a couple students made a loose ball while others made their foil into shapes that resembled their clay boat. Soon students were packing on as much as they could hold to see which boat would sink first. Near the end of class, students talked about how the shape of the sides determine how much cargo the boat will hold. We ran out of time but the class really wanted to test floating their boats in salt water!

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