## Learning by Degrees: Demonstrating How Temperature Affects Expansion

July 14, 2012

by: Jonathan Smith

I’m a big fan of applied science.  Whenever possible, I like my labs and demos in my Physical Science classes to be as “real-life” as I can make them.  One rich area for science application is the topic of thermal expansion of solids.  Once students understand the underlying principles of why solids expand as they warm, I can choose from a plethora of great examples to teach the concept.

Over the years I have put together a walk-around laboratory experience where students can see the concept of thermal expansion of solids in action.  Of course I have the standard bi-metallic strip and ball and ring demos, but I also include thermostats, a taken apart toaster, and my absolute favorite, the Large Scale Thermal Expansion Apparatus from Educational Innovations.

This demonstration dramatically shows the effect of temperature change on standard household plumbing. The apparatus comes as a set of 4 segments of plastic pipe with easy twist-connectors.  One end of the apparatus fits a standard plastic funnel; the other has a downward turned drain spout.  One of the segments has a “foot” attached to it, which allows the funnel end to be firmly clamped to a table or counter top.  The position of the pipe is then marked at one end with an “O”-ring and a mark on a piece of paper is placed beneath it.  A bucket is placed beneath the drain spout. Students then pour hot water (from tea kettle on a burner) into the funnel at one end of the pipe, which then slowly drains out of the other.   As the water heats the pipe, the pipe expands.  This expansion can easily be measured by comparing the location of the “O”-ring on the pipe with the mark on the paper below it.  My students are always amazed at how much the pipe actually expands.  Running cold water through will, of course, decrease the length of the pipe.

After my students have observed this demo, I like to have them think about the everyday problems this phenomenon may cause, such as creaking or broken pipes.  I also bring to their attention some of the common solutions to these problems, such as expansion joints, specialized piping that allows for expansion and contraction without allowing a pipe to lengthen, and saddle joints, specialized holders for plumbing that allow for the expansion and contraction of the pipe.

Last year I revisited this demo and decided to try and make it even more “user-friendly”.   Instead of the funnel, I connected the funnel end of the pipe to some plastic hosing that I then connected to a faucet from a sink in my room.  I used hose clamps and a laboratory faucet aspirator to make it all work.  As it happened, the drain end of the apparatus now ends nicely at the other end of my counter right over another sink!  Students can now simply run hot or cold water from the sink and watch the expansion.  Even without the other sink as a drain, it would have been easy enough to put a bucket on that end.

A friend of mine who works at a local university and is engaged in the STEM initiative periodically visits elementary schools with basic science apparatus.  He tries to bring in materials that elementary teachers would normally not have access to but demonstrates science content that is age appropriate.  He thought that the basic concept of thermal expansion of solids was a good fit for just such lesson.  We used my modified version of the thermal expansion pipe and were quite successful.  Not only did the students understand the basic concept being taught, but the change in the length pipe was so dramatic they showed complete engagement.

## Reinventing Morse: A Case in Educational Design and Teacher Tips

March 25, 2011

by:Benett Harris

If you are a science teacher who has ever taught a physical science class or attended a physical science workshop then you’ve probably done the activity where you wrap a piece of magnet wire around a nail and use it to make a paper clip or another flap of metal move in response to an electrical current flowing in the wire.  This experiment is often called “building a telegraph” and its a good way to illustrate electromagnetism.  The experiment usually goes over well with students, but from experience I’ve found that this simple activity has a lot of stumbling blocks for younger kids and have always thought that it should be possible to teach MORE with your half hour or less activity time.  To that end I’ve created the “Reinventing Morse: Build your own Telegraph” science kit.  This article will explain some of my educational design choices for the kit and give teachers or anyone using the kit for educational purposes a few tips to help them in the classroom.

Fun Fact: Even though making a piece of metal slap into another piece of metal using an electromagnetic field makes a click, this kind of simple apparatus is not actually a telegraph sounder.  To be a true telegraph sounder the device must be capable of making a click on both ends of its travel.  This is how a telegraph operator can distinguish dots from dashes, by noting the time difference between the up and down click’s for each “bit” of code that comes through.  Reinventing Morse is designed to operate as a real sounder because the arm makes a click on both ends of travel.

The First Problem With the Traditional Wire and Nail Experiments:

Magnet wire is simply copper wire that has a small diameter (a large gauge) and is coated with a varnish enamel that insulates it so that adjacent turns of wire won’t short together when wound closely into a coil as in an electromagnet.  Any teacher who has worked with kids and magnet wire will tell you that there are two problems with magnet wire.  Firstly, it’s difficult to remove the varnish so that the ends of the wire may be connected into a circuit.  The best way to do this is to use a knife but obviously this is problematic for elementary or younger students, and so sand paper is usually the next alternative.  The fact that most magnet wire is coated in a varnish that is the same copper color as the copper wire underneath means that its hard to visually inspect a wire to see that its ends are properly stripped or to notice when other areas of the wire are stripped and might short out if brought into contact with another wire.  Secondly, magnet wire’s small diameter makes it hard to wind a nice/clean coil with each turn beside the previous one.  I’ve seen a lot of student and even teacher wound coils that were more like a wad of wire than a neat and efficient coil.  The wire also kinks very easily and can break once its been kinked or twisted.  The result of these two problems is usually more time spent on troubleshooting continuity in a circuit or rewinding a coil than in actually performing an experiment and making observations.  (Granted, troubleshooting can be an important part of a science experiment too).

Magnet wire also has a third limitation in the classroom and that is expense.  It is usually difficult to recycle the wire for future experiments or between class periods because it kinks and breaks easily.  It also usually costs more per foot to replace than other kinds of wire.

To solve these problems with my Reinventing Morse kit I decided to make the kits work using ordinary hookup wire.  Hookup wire usually has a steel core (less expensive than copper) and is coated with a plastic insulator that is clearly a different color than the wire making stripping much easier.  It also hand winds into a coil a little easier and a little more neatly.

Teacher Tip: To improve coil winding (for neater more efficient coils) I also built in a coil winding arbor into the telegraph sounder mechanism.  This arbor works along with the coil winding bobbins included in the kit.  Simply place your hookup wire into the retainer clip in the coil and then place the coil into the coil winding arbor hole in the sounder.  {full instructions with illustrations are included in the kit’s manual} It’s possible for one person to wind the coil by themselves by using a screwdriver to turn the coil bobbin but it’s easier for two or more students to wind each coil.  One student can hold the sounder mechanism, another can turn the coil bobbin, and a third can guide the wire.  The end result, much neater coils done in less time.

The Second Problem with the Traditional Wire and Nail Experiments:

The traditional experiment of winding magnet wire around a nail and using it to make a piece of metal move is a great way to demonstrate qualitatively that electricity flowing through a conductor makes a magnetic field, however it does not leave much freedom for quantitative measurements, comparisons, or much actual scientific inquiry.  There just are not any variables that can easily be manipulated, rather just overall effects shown.  This may be fine for lower grades where you simply want to illustrate a point, but for middle and especially high school there should be more room for the scientific method and for recording data in the experiment.

Making it Quantitative:

To make my telegraph into a device that can produce measurable quantities I did two things.  Firstly, I used a sounder bar that can act as a lever when attached to a force gauge (or a force sensor from a data-logging or probeware set).  Secondly, I included two coil winding bobbins so that students can make two different coils of different measured lengths and then use a force sensor in order to determine the effect of wire length on magnetic field strength.

Teacher Tip: The coil winding bobbins can be used in two ways.  You can have the students make two different coils of different lengths (for example 20 and 40 feet of wire) and then test each one individually and record their observations on field strength (holding all other variables constant, most importantly the battery voltage powering the coil).  Alternately you can have students work in teams in a cooperative lab activity where one or two students wind a coil while another one or two students test a different coil.  In this way you can quickly move through multiple lengths in one lab period.  For example 10 feet vs. 20 feet vs. 30 feet and so on.  Using this second method a data table can be generated and then the trend graphed.

Teacher Tip: To measure the force of the electromagnetic field simply connect a force gauge to the sounder arm, engage the circuit so that the electromagnet is turned on, and while one student holds down the telegraph base another student can pull up on the force gauge until the sounder arm can be pulled away from the electromagnet.  A third student can watch the force gauge and record their observation.

Going Further (The Kit Can Do More):

I wanted my kit to have application in the home/hobby/science-fair market, and I also knew that  teachers are on a limited budget and would want the most “bang for the buck” and so I wanted to make sure that my kit could be used to teach more concepts than simple electromagnetism.  One extension was the addition of quantitative measurements as mentioned above.  Another extension is the ability to use the telegraph mechanism to teach simple circuits and switching.  To do this I made the sounder arm and the up/down stops act as an electric relay (an electromagnetically controlled switch).  Relays are useful for teaching switching concepts like those used in computers or to control electrical appliances and can be a more fun way to teach simple electric circuits along with electromagnetism.  In addition multiple kits can be connected together using some as relays to form a complete communications system {more details and instructions are in the kit’s instruction manual}

Don’t Forget the History Lesson!

Reinventing Science kits are designed to integrate history and invention and explain how real world technology works in order to make the science lessons more relevant and more exciting to students.  In our modern world of instant personal communications via cell phones, the internet, and other technologies, students may take the history for granted but in practice I’ve found that students are very fascinated to learn how communications have evolved.  It’s easy to get students into the right mind set by getting them to imagine a world where communications meant talking in person, sending mail or messages by messenger, and waiting hours, days, or even months to find out local news let alone world news.  Another link between the past and present can be made via the idea of encoding messages and “codes.”  Many students, especially older ones will have cell phones and will be used to the idea of “texting.”  Along with “texting” comes the idea of symbols and abbreviations like “LOL” for Laugh Out Loud.  It’s not too much of a stretch to explain “SOS” and how it related to something like the Titanic disaster.  You can then show Morse Code for SOS and LOL together and talk about time savings in coding messages.

Anatomy of a Real Telegraph, permission to use granted by Harris Educational

Using the Reinventing Morse Kit can be a great opportunity to partner with History or Social Studies, English, and Math teachers at your school.  The History lesson can be about the Telegraph and how it changed the world.  It has been called “The Victorian Internet.”  The English lesson can involve writing about the history of the telegraph and how it relates to text messaging today.  The Math Lesson can involve taking the data from the science experiment, constructing a data table, and then relating that to a simple linear equation and demonstrating slope.  You can even go further… measure 10 feet of wire and 30 feet of wire, and then create a graph, then use the predicted value for 15 feet and compare against observed measurements.  The possibilities are really endless!

Fun Fact: Samuel Morse’s telegraph was not the first telegraph or the first electrical telegraph.  Many systems existed in prototype stages but all were limited by technological hurdles.  One system used electrolysis of water to make bubbles in test tubes that each were labeled with a letter of the alphabet.  This system was limited by the fact that it needed 27 or more wires to convey all the letters.  Wire existed but it was expensive, imagine trying to run 27 or more wires between major cities in order to transmit letters one at a time via bubble!  Other systems used fewer wires but used a very primitive system of burying the wires underground pressed into lumber sealed with tar and pitch.  Over time water seeped into this kind of “insulation” and shorted out their system.  Morse was successful in being adopted as a technology because his system used only one wire that was placed on polls above the ground (eliminating the need for insulation or multiple wires).  The other part of his circuit used the earth as the ground.  Morse was able to use just one wire thanks to the use of Morse Code to encode each letter into a pattern of dots and dashes.  This concept of efficient encoding is still used today via the one’s and zero’s that make up binary codes, and are behind your ability to read this very blog!

More Information and Resources

As with all of my Reinventing Science kits, there is much more to each kit than what comes in the box.  I support educational users of the kits with many free resources online, a fan page and community on Face Book, and videos on YouTube.  Some of the resources available are a bibliography and reading list about telegraphs, electromagnetism, and invention, a list of science standards addressed by the kit, and other tips and tricks for using the kit.

Check out:

A Downloadable Specifications Page for the Reinventing Morse Kit

A Bibliography and Reading List for Reinventing Morse

Frequently Asked Questions and Troubleshooting Tips

A list of NSTA and ITEAA Standards Met by the Kit

An external Site with Telegraph History Information

An external Site with Telegraph History Information and Great Photographs

Thank you Educational Innovations for carrying Reinventing Science kits and for letting me reach out to educators via this blog.  Special thanks to teachers for taking the time to read!

If you liked this blog or the Reinventing Morse science kit, make sure to check out: Reinventing Edison: Build Your Own Light Bulb.

About the Author

Bennett M. Harris holds a degree in Technology Education from North Carolina State University and has many years of experience developing educational materials, teaching, and tutoring students of all ages in many different STEM (Science, Technology, Engineering, and Mathematics) topics.  Bennett is the founder of Harris Educational and the originator of Reinventing Science kits.