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This post was written by Children's Museum Blog Ambassador, Nick Downey. Follow Nick's posts on the blog or follow him on Twitter @DadWithaBlog.
When we heard that The Children's Museum was adding the new exhibits Beyond Spaceship Earth and Alien Worlds and Androids, the kid in me got really excited. Like many young boys, I had a love affair with space as a kid. My dad and I had fun watching Halley's Comet fly past Earth in 1986, and the science fiction films of the era played no small role in my fascination. I've tried to share the joy of exploring the night sky with my own kids, and these two exhibits provide excellent outlets for just that!
We've already been through Alien Worlds and Androids, where we learned all about robotics and planets. My kids were excited to see all the androids on display, explored the planets in our solar system, and sat down to watch a movie from NASA about the Mars rover. I also have the opening date for Beyond Spaceship Earth marked in my planner so we can go explore the real adventures and exploration going on in space as soon as the doors open!
When our last visit was over, I remembered a science experiment I've been wanting to do with the kids that was the perfect tie-in to the exploring we did at TCM. My son is ALWAYS asking me questions about science. "Dad, how does an airplane fly?" (Aerodynamics) "Dad, why do I always get pulled to the side when we turn a corner in the car?" (Physics) "Dad, what makes this motor turn?" (Electricity) "Dad, why do round things float?" (Density) Well, this experiment deals with surface tension. Today, we made planets of our own with milk, food color, and a little bit of dish soap!
Before we began, we had to gather the ingredients mentioned above, plus a few lids and cotton swabs. Each kid got a couple lids, into which they poured a little milk (whole milk works best), just enough to cover the bottom of the lid, then added a drop or two of each color they wanted for a planet. Next they dipped their cotton swab into the soap and stuck it into the milk.
The food coloring immediately repels away from the dish soap on the cotton swab. If you twist the swab, you can get the colors to twirl around as well.
Try different color combinations and amounts, as you can get some really fun patterns to emerge. Once we had some planets we liked, we talked a little about the science behind it. The milk and food color have different surface tensions, and when you first add the color, the milk doesn't want to let it in. The soap however, breaks the surface tension of the milk and allows the color to flow freely through it. By turning the cotton swab, or by putting it in at different places, you can control where the colors then go.
Surface tension is what causes milk or water to bead on a smooth surface. If you look at a glass of milk closely, you'll see what looks like a thin skin on the top of the milk. The soap breaks up the fat molecules making up this skin and allows the food coloring which is less dense to disperse throughout. The more fat in the milk, the more action you'll see with the food coloring.
