Have Fun with Firework Science! (continued)
Topics: Second Grade, Science, July 4th/Independence Day
This experiment is a demonstration of that old scientific truth: “oil and water don’t mix.” Another important scientific property being demonstrated here is the movement of liquid molecules and the effects of "relative density." Oil molecules like to stick to other oil molecules more than they like to stick to water molecules. Likewise, water molecules are attracted to other water molecules more than they are to oil molecules. Left to their own devices, oil and water will push each other away and try to get as far away from one another as possible.
When you pour the food coloring into the oil and shake it, the two will mix briefly, but the mixture is quite unstable at this point. Then, when you pour the oil onto the water, it will break up at first, but as you continue to watch, you'll see the oil molecules find one another and begin to come back together. Finally, the water-soluble (meaning "water-liking") food coloring finds its way out of the oil, and heads back into the water, one color at a time, offering an extra art lesson in the ways that primary colors combine and separate. In the spirit of adventurous scientists everywhere, you can encourage your child to try this experiment several times, with lots of colors!
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Julie Williams, M.A. Education, taught middle and high school History and English for seventeen years. Since then, she has volunteered in elementary classrooms while raising her two sons and earning a master's in school administration. She has also been a leader in her local PTA.
Comments from readers
Thanks very much for the great idea. : )
3rd grader Eva says, "They looked kind of like fireworks. If you stir it all together again at the end, it turns blackish green! "
1st grader TJ says, "it was weird and sort of cool because at the first part it looked like squids and jelly fishes were going up - and also at the end of the jellyfish part they started to look like comets"
Also noticed that some colors disperse more quickly than others which lead to some creative guesses as to why.
What was fun at the end was their reaction when I showed them what adding a single drop of dish soap to the top would do to the oil. I had cheers for "Again! Again!"