Ron as Paracelsus for his high school Chemistry students

In 1994, Educational Innovations was founded by Ron Perkins, an award winning Chemistry Teacher from Greenwich High School. Along with a number of other awards, Ron was Connecticut’s first recipient of the President’s Award for Teaching.  He was not only a renowned educator, but Ron was also an incredibly creative presenter.  Ron’s passion for science and teaching took him around the globe, giving over 800 teacher workshops for teachers of elementary grades through college!  It was because of his impressive and dynamic presentations that Educational Innovations came to be.

When preparing for his classes and workshops, Ron would hatch ideas, gather materials, and then tinker in his basement.  His demonstrative presentations always generated Oooooooh’s and Aaaaaaaah’s from the people in attendance, whether young students or seasoned teachers.  When the smoke cleared and echoes stopped, teachers would crowd around him and ask where they could find the materials that he used to generate so much science excitement.

Responding to the needs of these other educators, Ron finally put together a two-page flier with the materials, and teachers would send checks or even cash through the mail, and Ron would send their packages.  In the early days, Ron would wait for the mailman to arrive, hoping for an order.  Now almost 20 years later, Educational Innovations supplies teachers, parents, schools, and workshop presenters from every state in the US and over 69 countries around the world!  We are proud to carry forward the spark that ignited interest in science for generations of students.

Ron's high school science fair entry

What is a Radiometer?

The radiometer is a light bulb-shaped device containing an object that looks like a weather vane (wings arranged in a circle like spokes of a wheel).  Developed to measure the intensity of radiant energy, or heat, the radiometer will:

1. Help you understand the principles of energy conversion.
2. Show how heat and mechanical energy are products of energy conversion.

Most of us don’t realize how important energy is in our lives.  In actuality, every facet of our life involves energy.  One of the reasons we tend to take energy for granted is that it is constantly changing from one form to another.  We call this change conversion.

During this conversion, energy is changing to and from potential and kinetic forms of energy.  Potential energy is the energy stored in matter; kinetic energy is the energy of motion.  In all energy conversions, the useful energy output is less than the energy input.  This is because some energy is used to do work, and some energy is converted to heat.

Sir William Crookes invented the original radiometer in the mid-nineteenth century.  The device was developed to measure the intensity of radiant energy, or heat.

What causes the vanes of the radiometer to spin?  The atmosphere inside a radiometer is a nearly perfect vacuum.  More than 99% of the air has been removed, leaving only thousands of air molecules inside the radiometer compared to the trillions of air molecules in the outside atmosphere.  The “lighter air” inside the radiometer means that the air molecules are able to move about more freely.

The opposing sides of each vane within the radiometer are alternately dark and light in color.  As light (infrared radiation) hits the vanes, the lighter side reflects the light while the dark side absorbs it.  As the dark side absorbs the radiant energy, a difference in temperature develops between the vanes.  The freely moving air molecules bounce off the dark side with a great deal of energy.  As the air molecules “kick” away from the dark side of the vane, they form convection currents and momentum transfer causing the vanes to spin away from the side from which they kicked (that is away from the dark side of the vane).

Stronger light means that more energy will be absorbed on the dark side, and the air molecules will “kick off” faster and with greater force.  Therefore, as the light gets brighter, the vane begins to spin faster and faster.

Fun Activities to Try With Your Radiometer

Sunlight is responsible or many things, including the production of our food.  Plants use energy from the sun to drive the chemical change in the leaves of plants.  Plants act as an energy converter, and they can change the light energy into chemical energy that plants use to grow.

The following experiments also demonstrate an energy conversation.  This conversion begins with light energy that is changed into mechanical energy and heat.  In all energy conversions, the form of energy changes from a more useful type to a less useful type of energy.  Eventually all of the energy that we use will end up as heat, which is the least useful form of energy.

Always remember to be careful while using your radiometer.  Because it is made of glass, it may break if handled roughly or dropped.  If the radiometer does break, contact an adult immediately to clean the broken pieces.

Experiment #1

What light source works best?

Materials: Flashlight, lamp with an incandescent bulb, mirror

Put you radiometer under different light sources including sunlight.  Which light source makes the radiometer spin the fastest?

Experiment #2

What angle works best?

Hold the radiometer in different positions so light strikes it from different angles.  What angle gives the greatest motion to the vanes?

Experiment #3

Does a mirror increase the intensity?

Use a mirror to add additional light to the radiometer.  Does the mirror make the vanes spin faster or slower?  Why do you think that is?  Try holding the mirror at different angles to add light from different directions.  How does that change the rate of motion?

Experiment #4

Does the radiometer need direct sunlight?

Materials: Flashlight, lamp with an incandescent bulb, mirror, various colors of colored cellophane or colored plastic

Your goal is to find out if the radiometer still spins when the light source has to pass through a colored cellophane or colored plastic.  Use the different light sources from Experiment #3, but place the colored cellophane or plastic between the light source and the radiometer so the light has to pass through it.  Do certain colors allow more light though to make the vanes spin faster?  Do the vanes spin faster or slower with the colored cellophane or the colored plastic?

Experiment #5

The radiometer and heat energy.

Materials: Hair dryer

Use a hair dryer to direct a stream of heat toward the radiometer.  Do the vanes turn at all?  And if so, what happens after a few seconds?  How is this energy source (the hair dryer) different than light energy?

Experiment #6

Will wind affect the radiometer?

Materials: fan or drinking straw

Using the drinking straw or fan, blow air at the radiometer.  Can you get it to turn?  Why or why not?

Experiment #7

Your turn… Can you devise an experiment?

It is your turn to be the scientist.  Now that you know about the radiometer, can you devise an experiment using it? Decide what you’re testing for and test your results!

Educational Innovations sells radiometers for $9.95.

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 weeklong 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.

I would explain that the night before my winter trips, I could usually be found sitting on top of my very over-stuffed suitcase trying to close the latches!  I was always a little concerned that if the latch broke, my suitcase would explode and my belongings would be everywhere!  That always elicited a round of giggles as my kids visualized that catastrophe!  The interesting point was that once my suitcase was closed and latched, there was no way to determine how heavy it was just by looking at it.  Here it is… density in a suitcase!

The volume or size of my hard-sided suitcase never changed; however, the mass, or all the stuff inside each suitcase I packed was dramatically different.  This is when we started explaining more of the science of density.  The more tightly packed the molecules in an object are, the denser it is.

My next prop included two identical cardboard boxes.  The first had about eight bricks inside and the second was empty.  Without telling my class what to expect, I would ask for a volunteer to lift the box with the bricks.  After a bit of a struggle, the box would slowly rise above the table.  The other students could clearly see that the box was obviously very heavy.  I would then ask the same student to lift the second box.  Without fail, this box was hoisted so high that it almost flew out of the student’s hands!  Once again, we had two objects with basically the same volume but with drastically different masses.

My next question was: suppose my boxes were waterproof?  If I dropped them into the ocean, what would happen?  School aged kids all understand the concept of floating and sinking, so the obvious answer was that the box with the bricks would sink while the empty box would float.  I would explain that the bricks are denser than water, and that is why they sink. The air that filled the lighter box was less dense than the water, however, and therefore it would float.

In the next demonstration, I found two stainless steel spheres from Educational Innovations.  One was small and solid and the other one was much larger and hollow.  I would pass these around the classroom and asked the students to tell me which one had more mass (or was heavier).  Another unanimous answer:  the small, solid sphere was heavier.

Next, I would find another volunteer and blindfold my victim… I mean, my student.  I would then take two identical baskets, paper plates, or small plastic bowls and put each sphere in so they didn’t roll around.  I would ask my student to hold out his or her hands and would then place one plate in each hand and ask which was heavier…  Since both spheres are basically the same mass, the answer did not come as quickly as it did before the mass was spread out along a greater distance.  This was a perfect segue into the next unit on pressure.  But that would have to wait a week or two…

Of course, the observers in class were chomping at the bit to try the blindfold test.  Talk about active learning and a discrepant event!  Now that the class believed that both spheres were the same mass, I pulled out the large glass bowl filled with water, and I would ask my students to predict, based on the fact that we know that both sphere have the same mass, what would happen when I placed each sphere into the water.

This was amazing because, had I asked prior to blindfolding them, every student would have accurately predicted that the small sphere would sink, and the large one would float.  Now, a heated discussion usually ensued.  At this point, the mathematical formula was revealed (D=m/V).  When the mass increases and the volume remains the same, like the example of my luggage or the boxes with the bricks, the density increases.  At the same time, when the mass remains the same but the volume increases (like the small sphere vs. the large one) the density decreases.  Depending on the grade level I was working with. I would substitute simple numbers in the equation to show how changing the mass and volume affected the density.

Now, back to the discussion of floating and sinking spheres… After the explanation of how volume and mass affect density, most, if not all of my students agreed that the small sphere, being very dense, would sink, while the larger, lighter sphere would float.  Another successful seventh grade lesson!

One Pendulum…

Is interesting, but…

Two Pendulums…

Are much more interesting.

But Only If…

They are coupled together.

An Easy Way Is To…

Couple them at their pivot points.  This is accomplished by hanging the two pendulums from a horizontal string.

There Are…

Many illustrations of coupled pendulums on the web; search for ‘coupled pendulums’ – but the fine points of making a really successful demo are rarely discussed… so before we start:

Some Guidelines:

-       Make the pendulums absolutely identical: both the rod lengths and the mass values (the lengths are measured from the pivot points to the C.G. of the masses)

-       Use rod lengths of at least 1/3 meter (13”) – so the pendulums don’t swing too quickly

-       Use masses of at least 75 g (1 oz) – to provide a long swing time

-       Space the vertical supports for a horizontal string length of 500 to 600 mm (20 to 24 in.) – weighted or clamped-down ring stands will work – and will work especially well if their top ends are joined by a solid bar to minimize vibrations

-       The string should be fairly taunt – for example:  a 13 to 15 mm (1/2 to 5/8 in.) droop in the center with two 75 g masses hanging 100 mm (4 in.) apart

-       Use pendulum spacings of 75 to 125 mm (3 to 5 in.) – experiment for good results

-       For the best results, symmetrical setup spacing is critical – try to achieve positions symmetric within 4 mm (1/8 in.)

-       When pulling a pendulum to the side, two things are very important: first, don’t pull it too far (a mass rise of 75 mm (3 in.) is fine); second, the pendulum must be pulled at precisely a right-angle to the string

-       For the following exercises, when two pendulums are raised, they should be raised to the same heights

With Two Identical Pendulums:

Center the two pendulums with the pair spaced about 100 mm (4 in.) apart

-       (A.)  Raise and release one pendulum

Question:  What happens?  Why?

-       (B.)  Raise (on opposite sides) and release both pendulums

Question:  What happens?  Why?

With Three Identical Pendulums:

Center the three with a space of about 75 mm (3 in.) between each

-       (C.)  Raise and release the center pendulum

Question:  What happens?  Why?

-       (D.)  Raise and release one of the outer pendulums

Question:  What happens?  Why?

-       (E.)  Raise (on the same side) and release both outer pendulums

Question:  What happens?  Why?

-       (F.)  Raise (on opposite sides) and release both outer pendulums

Question:  What happens?  Why?

So Far…

We have dealt with identical pendulums… but what happens if we:

-       (G.)  Make a pendulum with a greater mass (but the same length) and use it in place of one of those

above

Question:  What happens?  Why?

-       (H.)  Make a pendulum just slightly longer (say, 20%) than one of the three and use it in place of one of

the pendulums above

Questions:  What happens?  Why?

In Action:

Construction Notes:

-       The horizontal string must be firmly attached (tied, hooked, or taped) to the vertical rods

-       The pendulum rods are made from coat hanger wire or from welding rod

-       Hooks are formed in the pendulum rods using a pair of pliers

-       The masses can be any object that can be affixed to the rod – preferably an object through which a hole can be drilled and, for easy identification during demonstrations, the masses should be different colors

In This Apparatus:

-       Length of horizontal string = 600 mm (23-1/2”)

-       Length of pendulum rods (from inside hook to far end) = 440 mm (17-7/16”)

-       Diameter and material of pendulum rods = 1/8” brass welding rod

-       Thread on end of pendulum rod = 6-32 for a length of ¾ in. (Note 1)

-       Nuts = brass 6-32 knurled (2 per rod)

-       Small mass = 5/8” x 2-1/16” steel rod (75 g) – 3 required (Note 2)

-       Large mass = 1” x 1-3/4” steel rod (175 g) – 1 required (Note 2)

-       Distance from inside of pendulum rod hooks to the centers of masses = 400 mm (15-7/8”)

Note 1:  A No. 6 screw diameter is 0.138”. – the 1/8 in. welding rod is 0.013” less – this is OK

Note 2:  Drilled thru No. 29 (0.136”)

A Comment on Dimensions:

The overall dimensions are not critical, but the apparatus should be large enough to be easily viewed in a classroom setting.

A Definition:

These are ‘Simple Pendulums’ because they are not ‘ideal’: i.e. their masses are not concentrated at single points and the restoring force is not a constant – however they do exhibit ‘Simple Harmonic Motion’.  This motion is an approximation at small angles – it is sufficiently accurate for our purposes.

And Further:

The details of Harmonic Motion and Simple Harmonic Motion are fascinating – the details of both can be found in any physics textbook.

‘Resonance’ is defined as the building up of large vibrations by the repeated application of small impulses whose frequency equals one of the natural frequencies of the body – in this case, a pendulum.  Identical pendulums are required to provide maximum energy transfer.  The mechanical energy is transferred by the ‘pulls’ on the supporting string – this is rather like a child’s swing where ‘pushes’ applied at the correct times will ‘add’ and act to increase the swing amplitude.

In Summary:

These demonstrations provide vivid illustrations of energy transfer between two and three resonant bodies.  Even better, additional pendulums, various masses, and variations of excitation will provide more interesting demonstrations and bases for experimentation.

Marty Sagendorf is a retired physicist and teacher; he is a firm believer in the value of hands-on experiences when learning physics.  He authored the book Physics Demonstration Apparatus.  This amazing book is available from Educational Innovations, Inc. – it includes ideas and construction details 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.

Science affects everything—yet so many of us wish we understood it better. Using an accessible question-and- answer format, 101 Things Everyone Should Know About Science expands every reader’s knowledge. Key concepts in biology, chemistry, physics, earth, and general science are explored and demystified by an award-winning science writer and a seasoned educational trainer. Endorsed by science organizations and educators, this book is perfect for kids, grown-ups, and anyone interested in gaining a better understanding of how science impacts everyday life.  101 Things Everyone Should Know About Science, written by Dia Michels and Nathan Levy is offered by Educational Innovations for $9.95.

Sample Questions!

1.  Name some characteristics of all mammals
2.  Name three of the bodily fluids
3.  What are the three states of water?
4.  What mineral is found in a saline solution?
5.  What do we use calories to measure?
6.  What happens over time when iron is exposed to oxygen?
7.  At the same pressure, which is more dense—hot air or cold air?
8.  How does a semiconductor work?
9.  Each year, Earth revolves once around what?

• the sun
• the moon
• its axis
• the Milky Way

10.  What are the four major directions? In which direction does the needle of a compass point?
11.  The continental divide separates:

• which animals are nocturnal and which are diurnal.
• the Northern Hemisphere from the Southern Hemisphere.
• the direction water travels to the sea.
• where it rains from where it snows.

12.  Why is it colder an hour after sunrise than it is at sunrise itself?
13.  What is a hypothesis?
14.  What is the goal of a double-blind, placebo controlled study?
15.  How can you use a lemon to light a light bulb?
 

Answers:

1. All mammals have backbones, are warm-blooded, have hair or fur, and drink their mother’s milk when they are born.

All mammals are vertebrates, which means they have backbones, unlike worms or insects. They are also able to maintain a constant body temperature, which is called being warm-blooded. Mammals have hair or fur at some point in their lives, and the females produce milk for their young through mammary glands. Mammals have large brains with modified skulls, complex teeth, and three ear bones. Their skulls have adapted over time to support their elaborate chewing muscles, and to better contain their large brains. Scientists believe that mammalian ear bones (the malleus, incus, and stapes) evolved from bones that were no longer needed, such as a bone to support gills. There are three orders of mammals: monotremes (egg-layers), marsupials (pouched mammals), and placentals (which account for the majority of mammals, including humans).

2. Blood, sweat, saliva (or spit), tears, breastmilk, semen, urine, mucus, lymph, plasma, serum, and digestive juices.

The human body is composed mostly of water, which our body uses to produce different fluids. These fluids help the body to work properly. Glands are organs in the body that create and release chemical substances through ducts. Glands produce sweat, saliva, tears, and breastmilk. Blood comprises two fluids and it also carries hormones, nutrients, infection-fighting cells, and oxygen. Plasma is the liquid component in the blood, while serum is the protein-rich fluid that remains after blood clots. Lymph is a milky fluid that contains lymphocytes, a type of white blood cell. It plays a critical role in the body’s immune system by filtering out and destroying toxins and germs. In mature males, the reproductive system produces semen, which contains the sperm needed to reproduce. Our kidneys process urine to carry wastes out of the body. Mucus is a thick secretion made by special tissues, including the inside of the nose and throat.

3. Liquid, solid, and gas.

Water exists in three states. We use the liquid state most often in our daily activities, for drinking, washing things, and cooking. Liquids do not hold a shape, but they maintain the same volume. In humans, liquid water makes up about 70 percent of our bodies. Ice, snow, and frost are frozen water. Water’s freezing temperature—the highest temperature at which water will become solid—is 32°F (0°C). Water vapor is water in its gaseous state. Until it reappears as a liquid or solid, it is invisible. Water evaporates into the air from bodies of water and from plant and animal respiration. Water vapor is an important regulator of the earth’s heat. Without it, and other so-called greenhouse gases, our planet would be very hot by day and very cold at night. A gas doesn’t hold its shape or maintain its volume. For example, if you pour one liter of water from a watering can into a bucket, it’s still one liter. If you take one liter of water vapor and release it into a two-liter bottle, it will spread out to fill the entire bottle. At sea level, water vaporizes at 212°F (100°C).

4. Salt.

Minerals (like salt) are natural compounds formed through geological processes. Saline is the term used to describe something, including a solution, that contains salt. The chemical name for salt is sodium chloride. Oceans are huge saline solutions, containing about 3.5 percent salt. Salt is also found in some rivers, lakes, and seas (e.g., the Dead Sea and Great Salt Lake). There are natural salt beds that are thought to have come from the salt water of evaporated ancient seas.

Salt manufacturers obtain salt either from these beds or by evaporating seawater. People have used salt as a seasoning and to preserve food supplies since ancient times. It was even used as money, in the form of salt cakes, by the Hebrews and other societies during Biblical times. There are references in the Christian Bible to salt and its value (e.g., “any man worth his salt.”) In Roman times, salt was an important item of trade and was used as money as well. Roman soldiers received part of their pay in salt, and newborn babies were rubbed with salt to promote good health. To compare a person to the “salt of the earth” is to say that they are valuable and have worth. Before refrigeration, rubbing salt into meat was the only way to preserve it. Salt is an excellent cleaning agent, drives away ants, is an effective antiseptic, and is used in skin treatments. Solutions of salts in water are called electrolytes. Both electrolytes and molten salts conduct electricity. Electrolytes also help the kidneys retain proper fluid levels and help balance the amounts of acids and bases in our bodies. They also help the cells in our bodies maintain a proper “voltage” so that the nerve cells can communicate with each other via electrical signals. Electrolyte drinks containing sodium and potassium salts are used to replenish the body’s water and electrolyte levels after water loss. Excessive water loss, resulting in dehydration, can be caused by exercise, diarrhea, vomiting, starvation, or surgery.

5. Energy.

We use calories to measure heat or energy. Scientists define the small calorie, or gram calorie (c), as the amount of heat it takes to raise the temperature of one gram of water 1°C. The large calorie, or kilocalorie (C), is equal to 1,000 small calories and is used to measure the amount of energy produced by the food we eat. Some items we consume have no calories, like water, coffee, or artificially-sweetened drinks, and provide us with no energy—although coffee and some diet sodas contain caffeine, which can create the illusion of energy. Other foods, such as cake and doughnuts, have lots of calories, but they provide little energy since they are very low in nutrients. These are known as empty calories. Any extra calories we consume beyond what is needed for our daily activities are stored by the body as fat.

6. It rusts.

Rust is the common name for a very common compound, iron oxide. For iron (chemical symbol Fe) to become iron oxide, three things are required: iron, water, and oxygen. Iron oxide, (Fe2O3) is so common because iron readily combines with oxygen (so readily, in fact, that pure iron is only rarely found in nature). Iron or steel rusting is an example of corrosion, an electrochemical process. Water speeds the process because it allows for the formation of hydroxide (OH-) ions. The rust that forms is much weaker than iron; when iron becomes severely rusted, it will crumble away. To prevent rusting (or the oxidation of iron), rustproof paint can be applied—a common occurrence on the Golden Gate Bridge in San Francisco. In other applications, nickel and chromium are added to iron to bind together the atoms and prevent them from rusting.

7. Cold air.

Cold air is more dense than warm air. Air is made up of nitrogen, oxygen, and other molecules that are moving around at incredible speeds, colliding with each other and all other objects. The higher the temperature is, the faster the molecules move. As the air is heated, the molecules speed up and push harder against their surroundings and each other. If the volume of the area is not fixed, this increases the space between the molecules, making the air less dense. For example, when the air in a hot-air balloon is heated, it expands (molecules speed up and spread apart). Now less dense than the surrounding air, the balloon rises. When the heater is turned off, the air in the balloon cools, the molecules slow down and move closer together, and the balloon descends.

8. By conducting electric impulses in a controlled fashion.

Semiconductors have had a monumental impact on our society. You find semiconductors inside most microprocessor chips—the heart of any normal computer. Anything that’s computerized or uses radio waves depends on semiconductors. Semiconductors, often created with silicon, allow the transmission and control of electric impulses in microscopic circuits. The smallness of these circuits has led to portable technology that could not have been built with the previous technology of vacuum tubes. For example, the computing power of a modern laptop computer would have required a large building full of power-hungry equipment and a large maintenance staff were it not for semiconductor technology. A diode is the simplest possible semiconductor device, and is therefore an excellent beginning point if you want to understand how semiconductors work. A diode allows current to flow in one direction but not the other. You may have seen turnstiles at a stadium that let people go through in only one direction. A diode is a one-way turnstile for electrons. Most diodes are made from silicon. You can change the behavior of silicon and turn it into a conductor by mixing a small amount of an impurity into the silicon crystal. A minute amount of an impurity turns a silicon crystal into a viable, but not great, conductor—hence the name “semiconductor.”

9. Earth’s orbit around the sun is called Earth revolution.

This celestial motion takes 365.26 days to complete one cycle. Earth’s orbit around the sun is not circular but elliptical. An elliptical orbit causes the distance from Earth to the sun to vary annually. Because Earth’s axis is tilted in relation to its orbit, the Northern Hemisphere receives longer and more direct exposure to the sun for half the year. For the other half, the Southern Hemisphere receives the warmer weather. The moon revolves around Earth much in the same way that Earth revolves around the sun, but it takes only 28 days for the moon’s revolution. Earth’s axis is the invisible line extending through its center from pole to pole. Earth spins, or rotates, on its axis one rotation every 24 hours, causing day and night. The Milky Way is the galaxy to which our solar system belongs.

10. The four major directions are north, south, east, and west; a compass needle points north.

A compass, often used when hiking or sailing, is a navigational tool used to tell direction. Magnets in the compass align themselves along a magnetic north-south orientation, which causes the needle to align with the magnetic North Pole, so it points north. The compass card inside the glass has the four headings shown as N, E, S, and W (going clockwise) and subheadings of northeast, southeast, southwest, and northwest. Numbers appear every 30 degrees. Long vertical marks occur every 10 degrees, with intervening short marks at 5-degree points. The compass card containing the magnets is mounted on a small pivot point in the center of the card assembly. This allows the compass card to rotate and float freely. The enclosure of the compass is filled with white kerosene to provide a medium to dampen out vibrations and unwanted oscillations. A lubber line is etched onto the glass face of the instrument to enable exact reading of the compass. When a compass points north, it is pointing towards magnetic north, or in the direction of the earth’s magnetic field. True north, also known as geographical north, is the actual northernmost point on the earth, or the center of the North Pole. The two measurements differ because the Earth’s magnetic “north pole” is actually in Canada. In order for an explorer to determine his actual location, he has to know the difference between true north and magnetic north, which changes depending on the longitude.

11. The direction water travels to the sea.

The North American continental divide is a mountain ridge that runs irregularly north and south through the Rocky Mountains and separates eastward-flowing from westward flowing waterways. The waters that flow eastward empty into the Gulf of Mexico by way of the Mississippi and other rivers. The waters that flow westward empty into the Pacific Ocean. Every continent with the exception of Antarctica has a continental divide. Some continents may have more than one.

North America also has an eastern continental divide, which runs along the Appalachian Mountains. Rivers to the west of this divide drain into the Mississippi and other rivers that flow into the Gulf of Mexico. Waterways to the east of the divide flow into the Atlantic Ocean.

Nocturnal and diurnal refers to the active time for an organism. An animal that is active during the day and rests at night is diurnal. An animal that primarily rests during the day and is active at night is nocturnal. The equator, an imaginary line drawn around the earth halfway between the north and south poles, separates the northern and southern hemispheres. Rain is liquid precipitation while snow is solid crystals. There are several factors that affect whether precipitation falls as snow or rain, such as temperature and elevation.

12. Because the planet continues losing heat after sunrise.

We think the minimum temperature should occur at sunrise because the earth has been cooling down all night. The temperature drops throughout the night because of two processes. The earth no longer receives energy from the sun, and the earth radiates energy to space. Overnight, the balance is strongly negative, and the earth loses heat. At sunrise, solar energy again arrives, but the heat loss due to radiation to space dominates until about an hour after sunrise. At that time, incoming solar radiation increases enough to overcome the radiational heat loss.

13. A proposed explanation for why something happens.

In common usage today, a hypothesis (which is Greek for assumption) is a provisional idea whose merit must be evaluated. Science happens in many ways. In some instances, a scientist observes a phenomenon—such as, food left at room temperature spoils more rapidly than food kept cool—and then develops a hypothesis for why. Other times, scientists set out to answer a question—such as, will mice be healthier if they eat vegetables or chocolate. Whether the hypothesis comes from an intellectual pursuit or an observation, the job of scientists is to perform tests in order to validate or negate their ideas. Through rigorous testing, scientists can help us learn what is speculation and what is real.

14. To eliminate the chance of bias.

In a single-blind experiment, the individual subjects do not know whether they are so-called test subjects or members of an experimental control group, but the researchers do. In such an experiment, there is a risk that the subjects are influenced by interaction with the researchers. This is known as the experimenter effect. Double-blind describes an especially stringent way of conducting a scientific experiment. In a double-blind experiment, neither the individuals nor the scientists know who belongs to the control group. Only after all the data is recorded (and in some cases, analyzed) are scientists permitted to learn which individuals are which. Performing an experiment in double-blind fashion is a way to lessen the influence of prejudice and unintentional cues on the results. Strictly speaking, in this type of experiment, every scientist who interacts with or treats a subject should be “blinded.” This doesn’t mean that they are really sight-impaired, it means they don’t know who is receiving a particular test or intervention.

15. Turn the lemon into a battery.

A lemon can be used like a battery by placing a copper penny and a steel paper clip (or a zinc-coated nail) into slits cut into the lemon skin, then connecting the penny and clip with a small piece of wire. The two different metals react with the acid in the lemon juice and cause electrons to travel from the negative terminal (the steel or zinc) to the positive terminal (the penny). An electric potential is created when the different metals are immersed in the lemon, and you can measure this with a voltmeter. One lemon alone will probably not produce enough power to light a bulb, but if you link four or more lemons together in a circuit by connecting the negative terminal of one lemon to the positive terminal of the next, and so on, you may get enough electricity to light an LED bulb, or some other small device.

Dia Michels is the founder and president of Platypus Media, an independent press in Washington, DC, whose goal is to create and distribute materials that promote family life by educating grown-ups about infant development and by  teaching children about the world around them. She is an award-winning science writer who has written or edited over a dozen books for adults and children. She has spoken at national and international conferences for such groups as American Association for the Advancement of Science, national Association of Biology Teachers, La Leche League International, Smithsonian Institution, and the Museum of Science.

Nathan Levy is the author of Stories with Holes, Whose Clues? and Nathan Levy’s 100 intriguing Questions. A gifted educator, Nathan worked directly with children, teachers, and parents in his 35 years as a teacher and principal. He has developed unique teaching strategies that encouraged the love of learning. He has also mentored more than 30 current principals and superintendents, as well as helped to train thousands of teachers and parents in better ways to help children learn.

Most everyone knows that an equilateral prism will refract white light into its constituent colors: a spectrum ranging from red to violet.  But, if one uses an additional prism, there’s much more to be discovered.

All that’s required:

-       a source of white light

-       a slit mounted on a large piece of cardboard

-       two equilateral prisms

-       two small pieces of card stock

-       a square of ground glass.

SIMPLE REFRACTION

The light source and slit are arranged as shown.  A fairly narrow (1/4”) color spectrum will be displayed on the ground glass.  Note that the light beams are DIVERGENT.

DOUBLE REFRACTION

The color spectrum from one prism is now passed through a second prism.  The various color beams are further spread to result in a somewhat wider (5/16”) spectrum display on the ground glass.  The light beams are even further DIVERGENT.

A SINGLE COLOR EXPERIMENT

Isaac Newton wondered if any single color of a spectrum could be further broken into more colors.  To investigate this, he placed ‘STOPS’ in the light beams between the two prisms – allowing only one color to pass to the second prism.  The result was that once white light was broken down into its constituent colors, the colors could not be further broken down.  Here only one STOP is used – leaving only red, with a small fringe of blue.

RECOMBINING SPECTRUM COLORS

Isaac Newton also wondered if the colors of the spectrum could be recombined to again make white light.  To do this he used a second prism arranged as shown.  He proved that this was possible.  What’s interesting is that the light beams exiting the second prism are not on the same line, but they are PARALLEL.  And, because the slit is not infinitely narrow, these beams are not infinitely narrow and therefore can mix to create white light.

THE COMPONENTS

• A 100 Watt halogen bulb provides a good light source.  It must be shielded because the room light should be a low-level to see the spectrums on the ground glass.  As shown, a box top is used – a fully enclosed bulb would be better, but there must be provision for removing the heat generated (about 90 Watts for a 100 Watt bulb).  Experiment to find a slit width that works well for your set-up.

• Two razor blades (single or double-edged) spaced with their edges about 1/32” apart make a good slit.  Tape the blades over a one inch by ¼ inch cutout in a piece of cardboard.  And be sure to use black tape to cover any openings in the blades.

• Two equilateral prisms.

• Two 3” x 3” square pieces of thin cardboard to act as STOPS.

• A 2” x 2” or 3” x 3” piece of ground glass or frosted vellum paper.  Ground glass is easily made using automobile engine valve lapping compound – place some compound between two pieces of ordinary window glass and rub them together.  Only one side should be frosted.  The sharp edges and corners of the glass pieces can be ‘broken’ with fine sandpaper wrapped around a small piece of wood.

NOTES:

A standard tungsten filament light bulb will not work as well as a halogen bulb – the halogen provides a much better spectrum.  Rotate the bulb to obtain the highest illumination of the slit.

The STOPS can be hand-held or taped to small blocks of wood.  In either case, the vertical edges that block the light must be parallel to the color lines so only one color is passed.

The ground glass can be taped to a small piece of wood – in this case, the vertical dimension should be increased to 3”.

It is important that the heights (the centerlines) of the bulb filament and the slit be the same.  And since the bulb’s filament will be four or five inches above the bench top, some large books or other flat objects can be stacked so the vertical center of the optical components match the center height of the slit.

The distances shown in the illustrations work well.  The distances to the ground glass can be increased for larger images, but with subsequent decreases of image intensity.  Obviously, a darker room will allow easier viewing of fainter spectrums.  As shown in this photo:

The spectrums shown are slightly curved because the prisms’ faces are very slightly curved.

IN SUMMARY

These are great demos in that they not only illustrate some fundamental properties of light, but that they also provide for many variations of the set-up.  The distances and angles shown provide a starting point for experimentation.  For example, increasing the distances will enlarge the spectrum display – but, which works best to do this?

IN THE CLASSROOM

These experiments can be done as a demo for the class as a whole, but even better, since the components are so inexpensive, several set-ups can be provided for lab groups of three or four students.  Equally fun for the instructor is the creation of the lab worksheet guiding the students through the investigations.

Marty Sagendorf is a retired physicist and teacher; he is a firm believer in the value of hands-on experiences when learning physics.  He authored the book Physics Demonstration Apparatus.  This amazing book is available from Educational Innovations – it includes ideas and construction details 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.

An Easy Question:  Which is warmer – which is cooler?

In the strictest sense, it’s a matter of energy.  And we use temperature as a measure of energy level.  As we all know, the greater the energy level, the higher the temperature… But, although this is absolutely true; sometimes it’s not exactly what we perceive in everyday life.  When asked, we all can testify that when we touch a piece of metal we’ll say it feels cold.  But is it really cold?  Is it or isn’t it ‘cold’?

The Answer Is…

… very simple.  If the piece of metal is at room (ambient) temperature it cannot be ‘cold’ – it must be at the same temperature as the temperature of the room.

But First:

Let’s discuss ‘perceived temperature’: this is what we ‘think’ the temperature is.  It isn’t always the actual temperature (of the object we touch).  Thus we enter a wonderful combination of both physics and biology.  Physics describes the absolutes.  Biology describes the biological reactions (interpretations) of our physical world.

It’s a matter of thermal conductivity and our nerves.  Some materials are good conductors of heat (energy) and some are not.  Our nerves sense only temperature – so if thermal energy is rapidly removed from the tissues surrounding our nerve endings (like at our finger tips), our nerves sense that the temperature ‘they feel’ is cooler – e.g. the material is removing thermal energy from the body tissue surrounding the nerve ends at a rate faster than our body can re-supply energy to the tissues – thus our nerves sense this as ‘cooler’.

Now:

A truly illustrative and memorable way to present the question:

Use a construction that provides a means of ‘feeling’ the temperature of three different materials: all three of differing thermal conductivities – low, medium, and high – a simple box having squares of ceramic, wood, and aluminum.  The ceramic and aluminum pieces exhibit nearly the same thermal conductivity, but the aluminum has just a little better thermal conductivity.  The wood has a relatively low thermal conductivity.

This box is 17” wide, 8” high, and 3” deep.

In The Classroom, Discuss:

Thermal energy in materials

Temperature (as a measure of thermal energy)

Conductivity (of thermal energy)

[note that you haven’t yet presented the biological aspect of the students’ upcoming measurement of what’s warmer or cooler]

The Exercise:

Begin by drawing a three column ‘Vote List’ on the classroom board (ALUMINUM – WOOD – CERAMIC).

[this is a little of a deliberate distraction, but flip the switch to ON and count to five seconds before starting]

Have the students, one-by-one, ‘test’ (by touching) the three materials and marking their vote on the board.

Total the votes.

Ask the class if this makes sense… that the aluminum (or perhaps the ceramic) piece is the coolest?  Ask, “Why is this so?”… “Is it because the metal or ceramic is heavier?”… Or, “Is it because the wood is darker in color?”

Now, turn the box to show its insides – that there’s nothing inside the box.  The three pieces of material MUST be at the same temperature! – Room Temperature.  If any students still doubt you, use an IR thermometer to prove your point!

And Finally:

The really fun part of the lesson:  Ask the class, “Why did so many people think that one material is ‘cooler’ than the other two materials?”  Don’t give the answer – guide the discussion – let the class discover the answer.

Marty Sagendorf is a retired physicist and teacher; he is a firm believer in the value of hands-on experiences when learning physics.  He authored the book Physics Demonstration Apparatus.  This amazing book is available from Educational Innovations – it includes ideas and construction details 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.

Educational Innovations’ Growing Spheres can be used to add a note of ‘horror’ to your classroom or home Halloween experience.  Once fully expanded, Growing Spheres have an index of refraction almost identical to that of water. This means that when the Growing Spheres are placed in water, they are nearly invisible.

Materials:

• A large (2 qt or larger) translucent plastic storage container and lid.
• Growing Spheres : GB-720 or GB-730 (these are the size used for the photos)
• Water
• Label for the container lid: GHOST EYEBALLS

Procedure:

1. Fill the storage container about ¾ full with water.

2. Add a pinch or two of Growing Spheres.

3. Wait about a day to let the spheres expand in size.

‘THE HORROR’

Place the container of ‘ghost eyeballs’ either on your school desk or at home on a table or chair on the front porch.  Place a ghost mask and/or ghost costume near the container of eyeballs.  Invite your students or trick or treaters to reach into the bowl and touch the ghost eyeballs.

CAUTION:

The eyeballs won’t be visible at first, but after several hand insertions, the water will get a little dirty and the eyeballs will be visible.

HUMOROUS FOLLOW-UP.

When I finished taking the pictures for this Blog entry, I put the Growing Spheres into the soil of a large plant we have in the house.  When we’re away for the summer, we leave the plant with a friend.  One day, after a rainy spell, our neighbor noticed the spheres sticking up out of the soil. “What,” she thought, “Snake eggs?”

So she rushed a sample over to a local nursery where she learned that these snake eggs were actually a form of water gel crystals.

What Are Water Gel Crystals?

When placed in water, over time these hard crystals expand to about 300 times their size, producing gel-like spheres. Students love to feel the slippery, spherical gel! The Large size start with a diameter of about 3.0 mm and end with a diameter of about 20.0 mm.  For a lesson activity, ask students to determine the change in volume, using V = 4/3 pr³.  These polymer spheres are great for starting seeds and growing plants so that the roots can be seen! They can be colored using food coloring. The polymer is similar to our super-absorbent, polyacrylamide polymer (#GB-5B and #GB-3) and can be dried and reused. These spheres are available in four sizes: Regular (~1.4 cm expanded), Large (~2.3 cm expanded),  Jumbo (~3.3 cm expanded) and Gigantic-Sized Spheres (start with a diameter of ~15 mm and grow to a diameter of ~57 mm!)

A Definition:

Clocks measure time – it can be a continuous measure of events passing or the measure of the interval between two events.

Of Hours:

After years of evolution, our modern clocks now divide the day into 24 equal length hours.  And, as we know, there are two systems in use today: Americans use the “double-twelve” system while the rest of the world uses the 24 hour system.

As An Aside:

The word “hour’ comes from the Latin and Greek words meaning season, or time of day.  A “minute” from the medieval Latin pars minuta prima (first minute or small part), originally described the one-sixtieth of a unit in the Babylonian system of sexagesimal fractions.  And “second” from partes minutae secundae, was a further subdivision on the base of sixty – i.e. “a second minute”.  (ref. Pg. 42 The Discoverers by Daniel J. Boorstin)

The “Double-Twelve” Clock Face:

Has 12 at the top – probably because at noon the sun is at its highest point in the sky.

But…

We can make a clock with 12 o’clock anywhere we wish and the clock will still work just fine.

Here we have a clock with 12:00 where 5:00 usually is.  Now, if the hour hand points to 12 and the minute hand points to 2, the time would be 10 minutes past 12.

Or:

We can rearrange the face:

Or:

We can replace the numbers:

Or:

We can divide the day into ten hours (times 2).

Suitable Clocks & How:

-       Good candidates are battery operated clocks with face diameters of 8 inches or less.

-       There are a variety of these clocks – all I’ve seen can be disassembled if one is careful.  When a front cover face must be removed, it is usually secured by three small tabs at the inner part of the face – use a worn common screwdriver to gently pry inwards, over a tab location, between the side of the cover face and the clock body – this will release the tab and allow the cover face to be gently ‘worked’ outwards.  Other clock designs are held together by multiple screws from the rear – be careful, some of these have real glass for the cover face.

-       The hands can be pried-off by using one’s fingernails on opposite sides of the hub of each hand.

-       A new dial face should be of ‘card stock’ (8-1/2” x 11” is readily available) – standard weight paper is too light.

-       A dial face must be a little smaller (1/16” on the diameter) than the opening into which it is placed – this will prevent buckling from expansion due to high humidity.

-       The dial face can be hand-drawn or computer-generated (using any of the popular computer drawing programs).

-       A punch or a craft knife can be used to cut out the center hole.

-       Sometimes the original dial face can be removed – sometimes not – it is not really necessary.  In either case, multiple small pieces of double-sided tape are used to fasten the new dial face.

-       When reinstalling the hands, they must be synchronized – the easiest way to do this is to set (press on) all the hands pointing to the (original) 12:00 position.

And More:

Over the years I, and my students, have made dozens of different clock faces – there seems to be never-ending variations.  You, and your students, will think of many different ones – just think of anything that represents numbers.  And, what’s neat is that each individual clock can have the maker’s name and/or school name included on its face.

Marty Sagendorf is a retired physicist and teacher; he is a firm believer in the value of hands-on experiences when learning physics.  He authored the book Physics Demonstration Apparatus.  This amazing book is available from Educational Innovations – it includes ideas and construction details 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 bottle balancer is a fascinating conversation piece that illustrates the principle of center of gravity!  A small hole in an oak board allows you to balance a 2-liter soda bottle at an angle that appears to defy gravity. This can be used as a teaching tool or a centerpiece at your next party!  Hold the special angle cut of the wooden, bottle balancer board against a flat horizontal surface.   When a full, sealed, 2-Liter soda bottle is inserted into the wooden hole from above, it will catch the bottle flange and the wood/bottle assembly balances at a surprising angle.

Explanation:

In order for an object at rest to NOT tip over, its center of gravity, or its center of mass must be directly over its base.   A goose-necked desk lamp is usually quite stable, unless it is configured so that the lamp part is stretched horizontally, far from the large base.  Then, it becomes less stable and often tips over.   The wood/bottle assembly example is more complicated than the lamp example because if the bottle is moved, the flowing liquid results in a change of its center of mass.

Consider a thought experiment!  To simplify the Soda Bottle Balance, consider the soda in the bottle frozen and the bottle super-glued to the wooden board so that everything balances on the angled edge of the board.  Balancing will only occur if the center of mass is directly above the flat angled edge of the wood.    How do you find the center of mass?  Loosely tie a string to your forefinger with a hanging weight tied to the other end of the string, e.g. a large metal nut or a bunch of washers.  Balance the object (in this case, the glued and frozen bottle balancer) on your forefinger above the string.    The center of mass will be somewhere along the straight line that includes the string.    Then, balance the wood/bottle assembly on your forefinger at a different point.    Again, the center of mass will be somewhere along the straight line that includes the string.    Where the two lines intersect is the center of mass.   This imaginary point must be directly above the object’s base in order for the object to be stable and not tip over.   Sometimes the center of mass is within the object and sometimes it is a point in space outside the object, as in the wood/bottle assembly.

What happens when you release the carbon dioxide gas from a balanced 2-liter soda bottle?   A sealed 2-liter soda bottle has a mass of more than 2000 grams of material and contains about 10 grams of carbon dioxide under pressure (Wikipedia).   If the bottle is opened and the gas released, the mass of the bottle becomes less by about 0.5%.   However, approximately half of this decrease in mass is to the left of the center of mass and half to the right. The release of gas results in very little change in the center of mass.   In trying the experiment, one must find a method of slowly releasing the gas in the bottle without disturbing its balance.   One method would be to make an extremely small hole in the balanced bottle by pressing a small hot needle into the bottle, allowing gas to slowly escape without losing liquid. This way the bottle assembly stays balanced as the gas begins to slowly leak from the bottle.   Observe what occurs!  Sounds like an interesting experiment!    Please let Educational Innovations know the results!

Note:   

As the pressure is released, the bottle may sag causing the soda to flow, drastically changing the center of mass of the bottle.   Also, if the gas is released too quickly, foaming will occur as dissolved gas quickly comes out of solution, resulting in loss of liquid.