Saturday, February 2, 2013

Science Saturday: Density Layered Liquids

Welcome back to the 2nd edition of Science Saturday! We're pleased to share with you another fun, frugal, and kid-friendly science experiment.

Hunter has been learning about density in Science, so Dad devised this cool experiment to illustrate the different densities of household liquids. It's loosely based on the oil and water experiment that you probably did when you were a kid, and also on a 7 layer density tower from Steve Spangler Science. (BTW, if you've never checked out Steve Spangler, you are missing out! That's our go-to site for fun science experiments and explanations.)

We used 4 ounces each of the following liquids: water, vegetable oil, rubbing alcohol,  and Purell hand sanitizer (or "sand hanitizer" as Madison calls it!). We colored each of the liquids with a different color food coloring. In retrospect, I wish we'd have used less food coloring, like only a drop or two per color.

We started by pouring the colored water into a glass jar. Rubbing alcohol has a lower density than water, so it should theoretically float on top. I say theoretically because what really happened was we poured a little too quickly, and the water and alcohol mixed. So did the two colors, producing a rather murky look.  But, hey, science is about experimentation and learning why things happen! It's not a failure; it's a learning experience! (You know, that's one thing I love about science- it's about the process, not necessarily the product.)

After doing a little reading, we decided that one of our tips for this experiment would be to pour SLOWLY, using a funnel. We also decided that we should have poured water, then vegetable oil, THEN alcohol. The water and alcohol really needed a buffer in between them. And, remember, only a little food coloring!

We topped our alcohol off with a layer of vegetable oil, then a layer of "sand hanitizer". It was really cool to see the less dense oil floating on top of the water, then the hand sanitizer, which appeared to be very dense, lay on top of the oil. The hand sanitzer formed a convex layer, which was very interesting to see. Since most of our alcohol was now mixed with the water at the bottom, we decided to add another layer of alcohol. We were very curious to see whether it would be more or less dense than the Purell, which is mostly alcohol anyway. The rubbing alcohol was, surprisingly, more dense than the hand sanitizer- it floated right on through it! Alcohol is less dense than oil, however.

After examining our layers, (in order of density from most dense to least dense was water, oil, rubbing alcohol, hand sanitizer) and discussing our results and how to improve the experiment next time (see notes above), we decided we simply had to shake it up!

Again, too much food coloring, so the mixed up version looked like what happens when you try to mix all the colors of Easter Egg Dye and wind up with brown eggs! But, after sitting for a while, the liquids still retain their original densities and will separate back out into layers.

You can try this density experiment with whatever liquids you have in the kitchen or camper. Milk, dish soap, laundry soap, honey, syrup, salt water, or whatever else you can imagine! Remember, Science Saturdays are about family fun, experimentation, and learning!

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