Sunday, while perusing the wonderful Pinterest, I stumbled upon this:
http://www.stevespanglerscience.com/content/experiment/colorful-convection-currents . Check out the video. (It is blocked at my school. Grrr.)
So, I decided to try this today with my students, since we are learning about Density. You must have containers with equal size openings. I luckily found some and filled two of them with cold water and two of them with hot water. I then put blue food coloring in the cold water and yellow food coloring in the hot water. (Forgive my pictures. I did not have my camera today, so these are phone pictures. My phone unfortunately does not take great pictures.)
My intention was to show the demonstration just as in the video, but we ended up just using the taller containers. (This was quite exciting for my first block.) I covered the cold water container with a note card and flipped it over. If you do this quickly, none of the water will spill, and the card will suction to the container. Then, I placed the cold (blue) water container on top of the hot and gently pulled the card out from under it.
Students remembered what they knew about cold and hot water and their density, and they made predictions about what would happen when the two mix. (Most actually predicted that I would make a terrible mess and didn't work. I proved them wrong!)
Students can easily see that the warmer water rises to the top, because it is less dense.
Next, students rapped (Yes, rapped. I forced them.) the formula for density:
Density = Mass
Volume
I found this great handout with practice exercises:
Rap on!
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