Monday, October 4, 2010

Density Column (Chapter 3, section 3)

The teacher's guide for CPO Earth Science is a wealth of information for the parent-as-teacher.  Each chapter section lists activites to motivate the student(s), explore, explain, extend and assess the topic at hand.  In section 3.3, the extension activity is to create a density column.

Given several liquids, the student is to predict which liquid will be the most dense and which will be the least dense.  When the liquids are poured into a graduated cylinder or other container, they will order themselves from least dense (top) to the most dense (bottom).

Daisy chose these household liquids: fake pancake syrup (don't judge--Costco was out of the real stuff), dark Karo corn syrup, lemon juice, canola oil, and water.  She predicted the liquids would order as oil, water, lemon juice, syrup and Karo. 

We used a large test tube to form the column.  It and other goodies were found in a box of supplies Older Brother had used to practice for a Science Olympiad event over the years.  Unfortunately, no graduated cylinder appeared so we pulled out the trusty medicine cup.

She carefully poured approximately 15 ml of each liquid into the test tube in order of lightest color to darkest color.  Here the Karo is making its way down the test tube:

We let everything settle while we ate lunch and ran to the grocery store.

An hour later:

Not bad!  Daisy had thought that the lemon juice would be separate from water.  I had her read the label---water, lemon juice concentrate...---"Oh! The water and the lemon juice mixed together!"  You can see the lemon solids suspended in the center of the test tube.  If the test tube was to sit undisturbed overnight, the solids would probably settle into a more defined layer instead of a blob.

Do some science!


  1. Ohh we've done this one! Great fun. And then we got to the point where we were just taking everything out of the cabinets and dumping it in to see where it settled--items, too, leaves, pennies, cardboard, whatever we found. Makes me want to do it all over again. ;-)

  2. Great lab! You make me want to do some science!

  3. Add small chunks of solids to see where they will settle: crayon, popsicle stick, noodle, etc.