Demonstrating Density: Who Knew They Could Be So Dense?


Tami O'Connor, Educational Innovationsby:  Tami O’Connor

Density is not typically an easy concept for most middle school students and even more difficult for younger students, but it doesn’t need to be.  We all know that D=m/V, but the easiest way I found to explain it to my students was to have them visualize a common dilemma in my home immediately preceding a vacation.  For years, as a poor starving teacher, I only had one suitcase, and it was actually a hand-me-down from my mother.  It was a medium sized Samsonite, hard cased piece of luggage.  When approaching the topic of density in my classroom, down from the attic it came.

My explanation began with an imaginary week-long summer vacation to a low-key resort.  The class and I would brainstorm the items I needed to pack for my trip.  Generally, the list included items such as a few bathing suits, shorts, t-shirts, a pair of flip flops, some PJs, underwear and a few toiletries.  It was obvious by looking at the size of my suitcase that in addition to my meager belongings, I could have probably also fit one of my students in my bag…  ok, perhaps one of the smaller kids.

I explained that when I closed the suitcase, it was hard to see, simply by looking at it, how heavy it was.  The lesson didn’t stop there.  We now planned my one-week ski vacation to Vermont during the February break.  Once again, my students and I made up my pack list.  The list included a couple of heavy sweaters, long johns, gloves, a hat, boots… as you can imagine, the list went on and on.  The question was, where to put it all.  Of course, since I had only one suitcase, the answer was easy. Read the rest of this entry »


Coupled Pendulums with Video


Marty Sagendorfby:  Martin Sagendorf

One Pendulum…

Is interesting, but…

Two Pendulums…

Are much more interesting.

 But only if they are coupled pendulums.

Read the rest of this entry »


Gro-Beast Alligators


Jill BrownBy : Jill Brown

Each year I purchase the Gro-Beast Alligators from Educational Innovations for my Fourth Grade class.  These growing alligators start at about three inches long and grow to over a foot long when placed in water!  From this one item, I have developed lesson plans that incorporate Math, Science, Reading, Social Studies, Writing, Technology, and Language Arts!Gro-Beast Alligator

Observation is the first action taken by learners to acquire new information about an organism; therefore, the first thing my students do is observe their polymer alligator.  The students in the picture below are in the process of measuring the length, weight, circumference, and area of their polymer alligators. Students in my class also trace their alligators on graph paper then they calculate the area of each and eventually compare the area of their small (dehydrated) alligator to that of their fully grown alligator. (Math & Writing & Language).  These measurements are compiled into a line graph for each student’s crocodile which aids students in making predictions about the rate of future growth of their growing reptile.  Read the rest of this entry »


The Law of Dulong and Petit


by: Dr. Jean Oostens

Atoms were proposed in antiquity without any experimental evidence by Democritus, a Philosopher.  This must have been a problem for Newton and Leibnitz who posited that there was always a mean of considering smaller and smaller intervals of space to calculate the “instantaneous velocity”.

The introduction of the precision balance in chemistry by Lavoisier paved the way for Dalton to formulate his laws on the “definite and multiple proportions” governing chemical reactions.  This supported the atomic theory, without giving it general acceptance.

Specific heat was defined as the quantity of heat needed to increase one gram of a substance by one degree.  There was no definite pattern when specific heats of various substances were compared.  Until two French scientists in 1819 calculated specific heat by atomic mass, forming the Law of Dulong and Petit.  There appeared a number of cases where the results were quite similar: about 6 calorie per mole.  This was equivalent to stating that any atom is as good as any other to store heat!  This was a small step towards acceptance of the existence of atoms.   An explanation for this, and the reason for the exceptions, had to wait the early 20th century explanation by Albert Einstein.  By that time, atoms had gained wide acceptance from the work of Rutherford, and soon by Bohr.

Lesson on the Law of Dulong and Petit:

You are given several chunks of metal, each containing 0.6 * 1024 atoms (i.e. one mole) of one element.   How will each of those samples, when dropped in a standard quantity of hot water (typically 200 mL and 70 C) affect the temperature?

Step 1.  Use a good balance (at least 0.1 gm resolution) to determine which element you are dealing with.  If possible confirm your identification with an additional cue. Read the rest of this entry »


Soil Porosity, Permeability and Retention Experiments


Cynthia Houseby: Cynthia House

Demonstration Materials:

  • 125 ml graduated cylinder or similar item
  • ~100 ml of pea gravel or small marbles
  • kitchen sponge
  • tap  water

Experiment Materials:

  • preforms and racks (three preforms/student or group)
  • fine gravel  such as aquarium gravel (~ 30 ml/student or group)
  • coarse sand* (~ 30 ml/student or group)
  • fine sand* (~ 30 ml/student or group)
  • small plastic cups ~ 100 ml capacity
  • squares of tulle (“bridal illusion”) and organza, ~ 10 cm x 10 cm
  • rubber bands
  • electronic balance (capacity at least 100 gm)
  • one pound margarine tub or similarly sized plastic cup per balance**
  • stopwatch or count-up timer (MyChron Student Timer)
  • 125 ml graduated cylinder or similar item
  • calculators
  • tap water

MyChron Student Timer

* Home centers sell sand for sand boxes, landscaping, paving, mortar etc.  Beaches are another source, although you may encounter undesirable contamination. Sifting non-homogeneous sand with a fine kitchen strainer may yield two usable grades of sand. 

** secondary containment to prevent accidental spillage of water onto the balance

Background Soil Vocabulary:

Porosity is the measure of how much groundwater a soil can hold, permeability is the measure of how quickly water passes through a soil, while retention is the measure of how much water stays behind.  Even elementary students can relate these concepts to their everyday lives. They observe that some areas in their yards or school grounds form puddles while others drain quickly after a rainstorm. They may wonder why one neighbor’s garden and yard remains lush and green although a sprinkler is rarely used. Children in communities dependent upon well water can understand the importance of replenishing the water table. In most rural and many suburban areas, homes use septic tanks and drain fields to process household wastewater. The “water cycle” is a topic in elementary science curricula. There are many excellent age-appropriate online sources for information on these topics including the United States Geological Survey (USGS) and the GLOBE program. Read the rest of this entry »