Seven Layer Density Column
Anyone can stack blocks, boxes, or books, but only those with a steady hand and a little understanding of chemistry can stack liquids. What if you could stack seven different liquids in seven different layers? Think of it as a science burrito!
- Light Karo syrup
- Vegetable oil
- Dawn dish soap (blue)
- Rubbing alcohol
- Lamp oil
- Graduated cylinder
- Food Coloring or True Color Coloring Tablets
- Food baster
- 9 oz portion cups
- Measure 8 ounces of each type of liquid into the 9 ounce portion cups. You may want to color each of the liquids to make a more dramatic effect in your column. Light Karo syrup is easier to color than dark syrup. The only liquids that you may not be able to color are the vegetable oil and the honey.
Start your column by pouring the honey into the cylinder. Now, you will pour each liquid SLOWLY into the container, one at a time. It is very important to pour the liquids slowly and into the center of the cylinder. Make sure that the liquids do not touch the sides of the cylinder while you are pouring. It’s okay if the liquids mix a little as you are pouring. The layers will always even themselves out because of the varying densities. Make sure you pour the liquids in the following order:
- Karo syrup
- Dish soap
- Vegetable oil
- Rubbing alcohol
- Lamp oil
- As you pour, the liquids will layer on top of one another. After you pour in the liquids you will have a seven-layer science experiment - a science burrito!
How Does It Work?
The same amount of two different liquids will have different weights because they have different masses. The liquids that weigh more (have a higher density) will sink below the liquids that weigh less (have a lower density).
|Dawn Dish Soap||1.06|
|Light Corn Syrup||1.33|
To test this, you might want to set up a scale and measure each of the liquids that you poured into your column. Make sure that you measure the weights of equal portions of each liquid. You should find that the weights of the liquids correspond to each different layer of liquid. For example, the honey will weigh more than the Karo syrup. By weighing these liquids, you will find that density and weight are closely related.
** NOTE: The numbers in the table are based on data from manufacturers for each item. Since each manufacturer has its secret formula, the densities may vary from brand to brand. You’ll notice that according to the number, rubbing alcohol should float on top of the lamp oil, but we know from our experiment that the lamp oil is the top layer. Chemically speaking, lamp oil is nothing more than refined kerosene with coloring and fragrance added. Does every brand of lamp oil exhibit the same characteristics? Sounds like the foundation of a great science fair project.
The table shows the densities of the liquids used in the column as well as other common liquids (measured in g/cm3 or g/mL).
Density is basically how much "stuff" is smashed into a particular area... or a comparison between an object's mass and volume. Remember the all-important equation: Density = Mass divided by Volume. Based on this equation, if the weight (or mass) of something increases but the volume stays the same, the density has to go up. Likewise, if the mass decreases but the volume stays the same, the density has to go down. Lighter liquids (like water or rubbing alcohol) are less dense than heavy liquids (like honey or Karo syrup) and so float on top of the more dense layers.
Have you found a way to make more than seven layers in your column? Let us know, we would love to hear your success story! Email us at firstname.lastname@example.org
So, we've had the density column sitting in our office for a few days now and have noticed a very interesting change... the layers of vegetable oil and rubbing alcohol have switched places. The rubbing alcohol is now below the vegetable oil, indicating that the density has changed. We are not exactly sure why the change occurred.
Since posting this observation, our email box has been flooded with hypotheses. Thanks for all of the valuable input we've received! Here are some of your ideas:
Hey science guys -
I have colored vegetable oil using powdered tempera paint. Every year one of the first activities I do with my preschool class is a color mixing experiment. I call over 2 children at a time. I have already dyed 3 small glasses full of water - one each red, yellow, blue - using regular food colors. I also prepare 3 small glasses of veggie oil and dye those the same red, blue, yellow with powdered tempera paint. Then I have one child pick a color of water and the other pick a different color of oil. We pour them into a baby soda bottle half of each liquid. Obviously it doesn't matter which one goes in first since the oil floats. After the cap is securely on, we predict what will happen when we shake it. Then I let the kids each have a turn to shake it and voila! - we have a new color! Of course, after it sits for a while, the mixture goes back to the original 2 colors. I leave it out all year - the kids love to go back to those tubes and shake them up just to see what happens!!
As the alcohol in the alcohol solution evaporates what is left is water. This will eventually make the alcohol solution sink down to the water level. Of course by this time the alcohol solution won't really be alcohol but water. So these are my thoughts on the seven layer density experiment. BTW my daughter did something very similar to this for her science project a few years ago. She had bystanders figure out which solution was which by looking at the chart for density and seeing which solutions sank and which settled higher.
Mom of 4 (soon to be 5) and
Elementary School teacher
Likely water has been absorbed by the alcohol layer.
So the question is how to test this hypothesis?
We could use a small pipette to remove part of the alcohol layer and measure the density, but we already know the density changed.
Perhaps we could the color change of cobalt chloride (red = water, blue = no water). I think some silica packing still has the color crystals
to show this change.
West Grand High School _______________________________________
It would seem the only way for the alcohol to change positions would be for it to change density......if something could be added or subtracted the density could change. If the alcohol is actually a mixture of alcohol and water, then the water and the alcohol could be evaporating from the mixture at different rates, that could change the density. That’s my hypothesis.
Arch Ford Education Service Cooperative
______________________________________ Hi, I just read about the alcohol and vegetable oils switching spots in your density demo. I am not sure this is a guess, but alcohol evaporates at a faster rate than many other liquids, right? I believe the carbon can’t bond to the hydrogen (not sure if that is exactly right, I thought I read that once somewhere), therefore the gas component in it is evaporating. If that’s the case, wouldn’t the liquid being left behind be more compact and have a heavier density?
Hope I’m not totally off base, if I am I will need to get a rag to wipe the egg off of my face…lol. I’d love to know the answer.
Ali (Atomic Ali)
Try putting just vegetable oil and rubbing alcohol in a column and then capping the column. The idea here is to exclude water. I think some water may be diffusing into the rubbing alcohol which is usually a 70% solution of isopropyl alcohol in water, and increasing the density slightly.
Department of Chemistry
University of Minnesota
OK, when you add alcohol and water, the alcohol fits in beween the water molecules, right? I wonder if the alcohol simply falls between the molecules of the other substances?
When alcohol and water mix the resulting volume of the two solutions is less than the total of the individual volumes. In this case "one plus one" does not equal two. The reason for this decrease in volume can be attributed to the hydrogen bonds which develop between the alcohol molecules and the water molecules (See "Surface Tension of Water" to see a further explanation of hydrogen bonding). This hydrogen bond pulls the molecules really close to each other and the small water molecules will fit nicely in the spaces between the alcohol molecules.
Having read the reference above, I have revised my thoughts. How about if the alcohol slips through each of the substance molecules, making temporary bonds as it passes down through the column?
Perhaps some of the vegetable oil dissolved into the rubbing alcohol, increasing the density of the new mixture enough that it became denser than the oil. Did something similar happen with the dawn or either sugar and the water layer?
Hello Spangler Team!!
Just a quick thought on why the rubbing alcohol and vegetable oil may have changed places in your density column. Rubbing alcohol typically contains acetone, methyl isobutyl ketone, water and denaturants. Some of these compounds evaporate quickly (the acetone, for example) causing the rubbing alcohol itself to change. Since the major compound in rubbing alcohol is water, it makes sense that the density of the rubbing alcohol as it evaporates would change to be very close to the density of pure water (1.00) and making it more dense than the vegetable oil (density 0.91.)
Keep the great ideas coming!!
8th Grade Science Teacher
Auburn Middle School
- 7 layer density Review by Sharon Albanese
I can only get about a 5 layer density result. The directions are followed too. Any suggestions?
(Posted on September 4, 2010)
- Let's see how this goes... Review by Tristan
I'm going to try this science experiment today. Well I have to becuase it was my 8th grade science homework. I'll tell you how it goes when im finished... =)
(Posted on September 19, 2009)
- Density column Review by Anika
This is such a great experement and just to tell you, you can put objects in it too!Rad
(Posted on December 2, 2009)
- this is great! Review by Carlotta
I am going to use it this week for two science classes that I teach for homeschoolers - lots of boys and they will really be engaged!
(Posted on February 12, 2011)
- Thanks for this idea Review by Naureen (Aaryan's mom) from Texas
I am very excited to do this expirement with my 6 years old. He have to do one science project in Early Child Education School and I come across this one which looks amazing. I am about to order 500 graduated cylinder.
(Posted on May 5, 2011)
- Add a DIY hydrometer to the project! Review by Ylva
I did this with my 1st grade daughter for science fair. It was a hit with her, the other kids and the judges.
I do recommend a small change though! Instead of telling the kids the right order of the layers ask them to find it out themselves using a simple homemade hydrometer. It can be made out of a drinking straw and Play Doh. Have the kids pour each item into a narrow, tallish container like a glass or test tube then float the hydrometer in it and determine the relative densities. After that they can pour each layer into the tall column in the right orde using the information they uncovered.
We tried to figure out relative densities using a kitchen scale and it was not accurate enough but the DIY hydrometer was perfect!
(Posted on February 25, 2012)
- Exciting Stuff! Review by Cathy R.
I did this experiment with my 5th grade class. We didn't have an accurate scale available, so we poured 4 fluid ounces of each liquid first. I told them about density and that water had a density of 1. We used a balance scale to figure out the "relative mass" of each of the four fluid ounce containers to determine which we should pour in first. Oddly, the Karo syrup appeared "heavier" than the honey so we poured it first. It was so exciting for the kids when we poured the honey in and they traded places right before their eyes. Another exciting moment happened with our lamp oil. We only had clear lamp oil so the students wanted to color it purple. It didn't work! Instead, all the blue and red dye gathered together in the bottom of the holding container. We bounced out some theories about what would happen with the dye when we poured it in. The class erupted with thrilling shrills of excitement when the dye kept slipping past the various layers and stopped at the water turning the water purple-again, right before their eyes! We have left the layers alone for a number of days now checking each day as to "what" is happening to the various layers. Our alcohol layer is now paper thin and the honey and Karo syrup have basically merged together. The children have certainly been energized by this exciting exploration in density, and I can't wait until we get started on our next experiment!
(Posted on March 2, 2013)
- How Cool Review by Jake
I'll be using this experiment for school, I hope my teacher is stunned by how awesomely cool this is!
(Posted on March 23, 2010)
- Amazing!! Review by Olivia
This girl just got a 100 A+ doing this for science and my teacher loved it! She copied my idea and is going to show it to the other classes she has! Great idea to do this one!
(Posted on March 17, 2011)
- THANKS!!!!! Review by amanda
It worked wonderfully!! Thanks for the idea!!!
(Posted on May 24, 2012)