Monday, November 19, 2012
Invitation to play: Frozen colored water
As we often do with potentially messy activities, we took them out to the staircase, so as to wash off right after.
The first thing we noticed was that the color was kind of trapped in the ice. That the ice was not uniformly colored but that the food coloring was concentrated in the middle of the ice.
This led to some discussion, but I hypothesize that it has to do with the density of the two liquids. Food coloring is basically a pigment (presumably a powder) dissolved in water and this increases the density of the water. I guess that when water freezes, it freezes from the outside, pushing the pigment molecules to the still liquid portion, making the liquid more concentrated in the center.