I did this lab with middle school students today. We prepped the clear plastic cups with push pin holes and heated the salty water with a microwave. I used ice water for the fresh water. The results were vivid. I made the salty water red and the freshwater blue. The students were surprised that the drawings of their hypothesis were a murky purplish whereas the actual results were layers of red, white, and blue... success. These new ideas for labs are helping to make connections to oceans for the students.
Tue, 10/23/2012 - 19:00
Hi Anne~ Yes! It was really fun to watch the changes at 1 min, 5 min, 10 minutes and even the next day. There was a steady streak of blue (cold, fresh H20) in the middle for a while, until the red (hot salt H20) started to drop to the bottom. There was also a layer of original, clear water in the very middle when the blue began rising to the top. The next day it was a perfect bluish on top and darker red on the bottom; while the cups still had some color on the bottom, but they had filled up on the top about 3/4 with the clear water...very, very cool. I was able to do this with my 3, 4, 5, 6 ,7 & 8th grade Science classes!
Sun, 10/21/2012 - 09:31
Did the layers of red and blue rise/fall over time as the temperatures changed?