Sometimes science lessons come from simple accidents. When our oldest was 4, he put green food coloring in water and poured it into a wax-coated paper cup. He left it on our back porch, the temperature dropped and gosh were we surprised by the ice formation we saw the next day!It wasn't a uniform block of green ice at all--instead, it formed what you see in this photo. The ice is transparent with a spherical ball of food coloring in the center. When we tried to repeat this by putting another sample in the freezer we didn't get the same result--we just ended up with a uniformly-colored block of ice.
Why the green blob? We're not really sure. The food coloring contains proplylene glycol, which has a lower freezing point than water. Some food scientists at Ohio State University (where we were at the time) suggested that the food coloring is pushed inward as the water freezes from the outside in. To reproduce this effect, the water must freeze very slowly, as it will if you put it outside when the temperature is only slightly below freezing. So the fact that our oldest put the water outside was the key to this whole phenomenon.
He was always doing silly little "experiments" like this. I like to think that if I hadn't tolerated his little messes he never would have discovered this exciting surprise!
Great post, especially since I've seen a video of his high school science project! It reinforces the idea that those early leanings can become their passions later in life. Our pediatrician still says that A. was the only patient who asked for a volcano for his third birthday!
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