These flashy layered columns of household liquids make a colorful way to show how fluids with less density float on top of each other.  Young scientists can also practice making hypotheses while testing where different objects will settle in the layers. I recommend this activity for learners age 3 and up, because it takes a level of patience and restraint to create the layers (and not stick tiny fingers in the liquids!). 

LEARN SCIENCE VOCABULARY:

Density – how much “stuff” (or more scientifically, “matter”) is in a certain amount of liquid.  (Officially, density can be found by taking an object’s mass and dividing by its volume.) Density can be easily demonstrated by finding 2 objects of similar size but different weight, for example a small rock and a styrofoam peanut.  The rock has a higher density than the styrofoam because there is more matter crammed into its size.

Volume – the amount of space something takes up.  When you add objects to your finished density column, you may find that their volume displaces some of the liquid and your column will overflow!

MATERIALS NEEDED:

• Tall, thin clear container (I used a juice glass… you could also use a bud vase, a recycled jar of jelly or olives, even the plastic Bubble Wand containers that sell for 99¢ at Walmart  would work.  To get a good column, it helps if your container is taller than it is wide.)
• Honey
• Corn Syrup
• Milk
• Dish Soap
• Water
• Vegetable Oil
• Rubbing Alcohol (You can leave this out if your young scientist is prone to tasting the science experiments!)
• Food coloring
• Various objects for testing density (We used beads, pennies, peanuts, popcorn, gummy bears, Cheerios, Play-Doh, plastic toy, etc.)
• NOTE: You can still make the columns without all the layers; just skip the step of the material you are missing!

HOW TO MAKE IT:

1. Add food coloring to the water (we did blue) and the rubbing alcohol (we did red). (You can add coloring to any of the liquids if you want…this is really just for effect!).
2. Begin with the honey, since it is the most dense liquid.  Pour about 1/4″ in the bottom of your container.  Try to avoid getting it on the sides. (With younger kids, it is best that the adult pours the layers into the container, at least for the first try at this experiment.)
3. Add corn syrup next…I found it helpful to first pour it into a small cup in order to drizzle it lightly over the honey so they wouldn’t mix too much.
4. Let the 2 layers settle out, then carefully pour on the layer of milk.
5. Next add the layer of dish soap.  I poured it over a spoon (like I was pouring a Guinness, for any of you Irish beer drinkers) so that it would not mix in with the milk layer too much.
6. Add the colored water layer on top of the soap, again using the Guinness-spoon technique.
7. Add the oil on top of the water layer.
8. Finally top off your column with the colored rubbing alcohol.  Give the liquids a minute to continue to settle out and you should see a pretty neat division of DENSITY layers!

   

9. This last step is the part my 3-yr-old really enjoyed: He got to pick all sorts of items and drop them into the column to see where they would settle out in the layers.  I had him make a hypothesis as to where each object would end up based on our estimation of its density. (If you are planning to test a lot of objects, make sure you leave space at the top of your column for the rise in VOLUME! We had a bit of spill-over.)
   

   

THE SCIENCE BEHIND IT:

Everyone has heard the phrase “oil and water don’t mix.”  Well, it’s because of DENSITY! When liquids have different DENSITIES, the one with the lowest density (in this case, oil) will float on top of the other liquid (in this case, water).  This is because the more dense liquids are heavier (for the same amount of VOLUME).  In fact, if you stir up your density column and mix all the liquids together, you will find that after a while they will again settle out (more or less; some mixing will occur) into their original position.  The objects you drop into your column will eventually settle in the layer that most closely matches their own DENSITY.