## Eureka!

March 30, 2010

by: Cynthia House

I sponsor an after school Science Club in a K-5 elementary school. The club is organized into two-week-long sessions, each session focusing on a specific topic. One of this year’s most successful sessions involved the Archimedes Balance from Educational Innovations.

For week one, I prepared:

• calculators
• answer sheet, listing the sample materials and their densities
• fill-in table to record findings:

The table I provide includes simple, step-by-step instructions for students so they can easily determine measurements such as volume, mass and density.  For complete instructions including all charts, use this link.

Students worked in pairs with first and second grade children teamed with a fourth or fifth grade student. We introduced the topic with a brief Power Point biography of Archimedes and his accomplishments, focusing on the story of King Hieron’s crown. Then students practiced determining the density of materials using the Archimedes balance and the samples supplied in the sets (all directions are included in the kit).

The Archimedes Balance relies on Archimedes’ principle which states that a floating object displaces its own weight of fluid.  The balance consists of a graduated cylinder partially filled with water and a tube that fits inside the cylinder and can float in the water.  By placing an object inside the inner tube and measuring the amount of water displaced, you can easily determine the objects weight.

The fill-in table helped them remember what measurements to take when, and how to calculate results. I was surprised at how completely engaged all of the students were, and the accuracy of their results.

To prepare for the second week I assembled the following;

1. control samples: strips of zinc, copper, aluminum, iron, and  nickel metal (battery electrodes), and the brass and nylon cylinders from the Class Set of Six Archimedes Balances Classroom Set and Classroom Density Assortment.
2. samples of unknown composition including coins, screws, bolts and other fasteners, furniture hardware, machine parts, plumbing fixtures, etc. We had 18 different samples. For very small items, students used enough pieces to obtain accurate volume and weight measurements, for example, twenty pennies instead of one.
3. metric rulers, electronic balance, and micrometer
4. calculators
5. electrical conductivity tester made from a battery holder, tiny light bulb in a socket, wire, and alligator clips
6. magnets
7. graduated cylinders from the Class Set of Six Archimedes Balances Classroom Set
8. cylinder protectors (see drawing below)
9. fill-in tables to record findings

We started the second day by telling the students that the local library needed to obtain samples of items made out of zinc for a display of the chemical elements. Our Science Club had been contacted to find those zinc items.

Students began by determining the electrical conductivity, magnetic characteristics, and density of the control samples. Since many of the samples did not fit into the floating tubes provided with the Archimedes Balance sets, and to save time, we determined weight using an electronic balance. If volume could be easily calculated using measurements with ruler and micrometer we did so.

Having finished characterizing the controls, students now examined the assortment of items of unknown composition, choosing for themselves which items to investigate.  They were cautioned that some items may be lacquered, effecting conductivity results, or plated, effecting the color. Students determined weight using the electronic balance, and volume using the graduated cylinders. I thoroughly enjoyed listening to each team’s reasoning for selecting promising candidates. (The zinc sample was post 1982 United States pennies.)

## It Floats – Why?

March 25, 2010

by:  Martin Sagendorf

We often think we see forces.  However, in reality, we only see the results of forces.  To understand forces we must believe in Newton’s Third Law.  It states that all forces can only exist in opposite pairs and be equal in magnitude.  And… what is very interesting is that Newton’s Third Law does not stipulate that the forces be of the same kind.

Also, by Newton’s Second Law: If the (net) forces are equal, there will be no accelerations (Fnet = ma = 0)… in other words… equal and opposite (net) forces create a state of equilibrium.  An interesting example of equal and opposite (and unlike-type) forces is that exhibited by a combination of opposed magnetic fields within a gravitational (force) field.  These two different (types) of fields interact purely as ‘force fields’ – only their forces matter… not their types.

The Cosmic Magnetic Puzzle exemplifies a combination of such forces: a barbell containing two ‘donut’ magnets supported in mid-air above stationary pairs of magnets – with an additional pair of donut magnets maintaining the horizontal location of the barbell.

If you don’t feel like building this apparatus, there are commercially available products that demonstrate this concept at a smaller scale.  Educational Innovations carries the Revolution Top, which has flashing led lights that also demonstrates persistence of vision.

This Demonstration Illustrates:

• Attracting Magnetic Forces
• Repelling Magnetic Forces
• Balanced Magnetic Forces
• Gravitational Force
• Two Balanced Forces
• The Concept of Energy
• The Concept of Work
• The Concept of Equilibrium

• Will this work in space?
• How long will it work?
• How are the magnets’ pole faces arranged?

Guidelines for building the Cosmic Magnetic Puzzle are detailed in the book Physics Demonstration Apparatus.  This amazing book is available through Educational Innovations and includes ideas and construction details, including all equipment necessary, for the creation and use of a wide spectrum of awe inspiring physics demonstrations and laboratory equipment.  Included are 49 detailed sections describing hands-on apparatus illustrating mechanical, electrical, acoustical, thermal, optical, gravitational, and magnetic topics.  This book also includes sections on tips and hints, materials sources, and reproducible labels.

## The Sun’s Energy

March 25, 2010

by: Martin Sagendorf

Imagine students’ amazement when they actually see sunlight melt a penny!  This demonstration clearly illustrates the vast amount of energy illuminating the Earth’s surface.  In rough numbers: 70% of the Sun’s incident energy on our outer atmosphere is reflected back into space – only about 30% actually gets to the Earth’s surface.  But, as we experience, this is still a substantial quantity of energy.

Fortunately, this energy (I. R. – Visible – U. V.) is rather uniformly distributed over the Earth’s surface -  thus its overall intensity is such that we have a habitable environment.  However, as we all know, we can concentrate some ‘area’ of this energy to increase the ‘energy per area’ (a measure of this is the temperature of the area of concentrated energy).  A common magnifying lens (2-4 in. diameter) will concentrate sufficient energy to burn paper or other objects with a low flash point.

To achieve an even higher energy concentration it is only necessary to use a device that increases the ‘capture area’ of the Sun’s energy.  Fortunately, this is easily accomplished with an inexpensive (\$3.50) Fresnel lens.  The Fresnel lens (64 sq. in.) used here will ‘collect’ nine times the energy of a 3 in. diameter magnifying lens –creating a ¼” diameter ‘spot’ of energy having a temperature of over 315 degrees C (600 degrees F).  This is sufficient energy to melt zinc.

All that’s required are a Fresnel lens, bright sunlight, and a means of holding a penny.  Actually, it is a bit more involved: the Fresnel lens must be positioned exactly perpendicular to both the sunlight and the penny; the penny must be of 1982 or later; and the penny must be supported by a thermally minimally-conductive means.

Guidelines for building the Atomic Penny Vaporizer are detailed in the book Physics Demonstration ApparatusThis amazing book is available through Educational Innovations and includes ideas and construction details, including all equipment necessary, for the creation and use of a wide spectrum of awe inspiring physics demonstrations and laboratory equipment.  Included are 48 detailed sections describing hands-on apparatus illustrating mechanical, electrical, acoustical, thermal, optical, gravitational, and magnetic topics.  This book also includes sections on tips and hints, materials sources, and reproducible labels.

And, as a footnote, it is not illegal to ‘vaporize’ a penny or any other United States currency.  By law, it is only illegal to alter U. S. currency if the intent is to defraud – melting a penny with the Sun’s energy is simply a wonderful example of energy and its effects – perfectly legal.

## Teaching Observation Skills

March 9, 2010

by:  Matthew Campbell

One of the more important traits a scientist can have is the ability to observe.  Helping our students become better observers can be tricky.  Observation is a soft-skill and can be difficult to teach directly.  In my experience I also find that students tend to rush through labs to obtain the answer quickly.  This desire for speed is contrary to the pace required for careful, precise observation.

My solution for helping students become better observers is the science journal.  The purpose of the science journal is to encourage students to observe the science happening all around them.  The scope of the project allows for careful observations to be made which can then proceed into conclusions and validations of hypotheses. As an added bonus, the journal integrates literacy into the science classroom.  I encourage my students to select topics that appeal to them to increase investment in the project.   I do provide a listing of sample topics to help them better formulate their own journal topics.  Some of the topics covered in the journals have included:
    Reviewing newspaper/magazine articles for cases of good or bad science reporting
    Looking for science principles in sports (excellent for physics)
    Studying the changes in an ecosystem (e.g. plant growth, goose behaviour)
    Astronomical observations
    A recording of chemical additives found in the food that the student has eaten
    Beginning a new exercise regime
    Following weather patterns

The ideas for the journal are limited only by the student’s imagination.  I normally have the journal topics last for a unit or two, providing the student with a chance to study a different topic that may appeal to them.

A fantastic twist on the journal idea is to have the students blog their observations.  The integration of technology with journaling tends to improve student engagement. Additionally, the project gains credibility as it is now open in the public space and is no longer private between the student and teacher.  This interaction between the student and other Internet users helps the student desire to improve their writing, as they are now writing for an audience.  The student’s posting obtaining its first comment is normally a momentous occasion that only further entices the student to dig deeper on their topic.

There are numerous free blog hosting sites on the Internet, including EduBlogs, WordPress and Blogger.  Students can create their own blog or record their thoughts on a communal class blog.   Before starting a blogging journal, teachers should review the activity with administrative staff and ensure that parents are properly informed.  If there are concerns about personal information being revealed on the Internet, students can create an Avatar (I like DoppelMe) and use a pseudonym to write under.  If this approach is used, the teacher should keep a master copy of the pseudonyms for reference purposes.

Journaling, when combined with blogging, can be an excellent approach to improving not just observation skills but general science skills such as reporting, hypothesizing and drawing conclusions.  As an added bonus, the science of the classroom begins to filter into the students everyday experiences.