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.

About the author
Matthew Campbell is a certified Science and Mathematics teacher in Ontario.  He currently teaches at Conestoga College in Kitchener, Ontario.  His blog, http://shift-edblog.blogspot.com/ explores the usages of technology in the classroom.

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Posted by Tami O'Connor

Density Activities With The W-Tube

February 12, 2010

by: Tami O’Connor

The W-Tube is a device that was invented and developed by Ron Perkins, Chemistry and Physics high school teacher for 33 years and founder of Educational Innovations.  This amazing teaching tool was designed to have students in every grade level, kindergarten through high school, discover and gain a deeper understanding of concepts relating to density and air pressure.

In order to solve each puzzle, students need to have a basic understanding of density and air pressure.  Depending upon the grade level of your students, you may want to conduct a few experiments or demonstrations prior to having them attempt the W-Tube challenges on their own.  The following two activities do not utilize the W-Tube, however they will provide some younger students with the background knowledge necessary to successfully complete the W-Tube challenges.

This first activity is a valuable demonstration that shows that air takes up space.  Start by balling up a paper towel or tissue and affixing it to the bottom of a plastic cup using two-sided tape.  Invert the cup with the tissue inside and then push the plastic cup into a clear container of water so the cup is completely submerged.  Your students should be able to see that, although the air is somewhat compressed within the cup, the paper at the “top” of the cup remains dry.

The second activity deals more with density, or how tightly packed the molecules are in a given object.  An object’s density is determined by comparing its mass to its volume.  For example, if you have two objects of the same size, the heavier object is said to be more dense.

Pour equal amounts of corn syrup, water and vegetable oil, into 3 different but identical beakers, and, using a balance, find the mass of each liquid.  Then, gently pour the liquid with the second heaviest mass into the beaker with the liquid with the greatest mass.  Finally, add the third liquid, which has the least amount of mass, to the beaker.  The three liquids should remain neatly layered according to their density, indicating that the less dense liquid floats on the liquid that is more dense.  This activity can also be conducted using different colored water with varying amounts of sugar in each, which would change the liquid’s density.

The W-Tube Puzzle is an excellent addition for any science table and is also great to use with students working in small groups.  The apparatus (DEN-510) contains three connected tubes that form a W.  The central t-connector between the three tubes allows water and air to move through freely.  Because air and water each take up space, by capping one or more of the tubes, you can trap the air and/or water such that they are no longer able to flow freely.  This gives the student the ability to vary the amount of water and air in each individual tube.

Activity 1 – Air Pressure

Students, working in small groups, should use pipets to fill the W-Tube with colored water in order to replicate the following diagrams.  Students should check with the teacher before emptying the W-Tube and moving on to the next diagram.  By strategically placing a cap on specific tubes, one can trap water and/or air to fill the each tube at a different level.  See the diagrams below.  The challenges become increasingly more difficult as you move down the list.  If a group of students complete their challenges quickly, ask them to replicate Challenge #3 using only one cap.  It can be done, but it is more challenging!

Air Pressure Challenge #1

Air Pressure Challenge #2

Air Pressure Challenge #3

Air Pressure Challenge #4

Air Pressure Challenge #5

Air Pressure Challenge #6

Activity 2 – Density

Provide each group of students with a beaker of sugar, food coloring (red, blue, and yellow), 3 small cups, a pipet, a spoon for measuring and mixing, and a source of water. Using the W-Tube (and the caps needed), students should alter the amount of sugar in each cup of colored water to replicate the picture provided.  For example, since the diagram shows the blue water as the bottom layer, it is the denser liquid (and has the most sugar).  Encourage your students to use as few caps as possible to complete each challenge.  Students must keep the W-Tube apparatus firmly on the table at all times during the activity (no tipping except to empty between trials).  Advanced students should develop a written plan before attempting the challenge.

Density Challenge #1

Density Challenge #2

Density Challenge #3

Density Challenge #4

For more information, and/or to view the teacher’s and student’s guides, visit our website: www.teachersource.com.

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Posted by Tami O'Connor

Cartesian Divers

January 27, 2010

by: Ron Perkins

Cartesian divers are one of the oldest and most interesting toys you can build at home.  While they are easy to construct, there is a lot of science behind the workings of this deceivingly simple toy.  A Cartesian diver is an object whose density changes with pressure.  In fact, most Cartesian divers become denser as pressure is increased.  By constructing a Cartesian diver carefully, it is possible to make a diver that floats in water at atmospheric pressure, and sinks when the pressure is increased.

Water has a density of about 1 gram/ml.  Objects that have a density of less than 1 gram/ml float, while objects with a density greater than 1 gram/ml sink.  When using sealed divers, as pressure is increased, a Cartesian diver’s density might increase from about .8 grams/ml to 1.2 grams/ml.  When this happens, the diver sinks in water.  Cartesian divers often change their density by changing the amount of water they displace (i.e., changing their volume).  When the pressure is increased, the air inside the diver is compressed.  This compressed air takes up less space, and thus displaces less water.  As less water is displaced, the density of the diver appears to increase and the diver sinks.

Making Cartesian Divers

Materials:

1 Plastic Pipet (PP-222), 1 Ballast Nut (CD-3), Plastic Soda Bottle with Top, Candle, Scissors, Pliers, Water

Optional: Fizz-Keeper Pump Cap (CD-4), Food Coloring, Aluminum Foil, Hot Melt Glue Gun

Instructions

1.  With scissors, snip off all but 2 cm of the neck of the pipet.

2.  Screw one ballast nut onto the remaining 2 cm neck of the pipet.

3.  Fill the pipet bulb with colored water.  Note that the bulb must float when placed in a cup of water.  Experiment with different amounts of water, making sure that the bulbs still float.  Bulbs that float higher in a cup of water will make divers that are more difficult to sink.

4.  Your Cartesian diver is ready!  Fill a 1 or 2 liter plastic soda bottle almost to the top with water.  Place your diver in the bottle and screw on the Fizz-Keeper pump cap.  Try squeezing the bottle.  Can you make your diver sink?  Now pump the Fizz-Keeper and watch as your diver sinks right to the bottom.  Can you figure out how to get it back up to the top?

5.  Remove the pump cap, pour out your diver, and try varying its buoyancy.  Try filling it with different amounts of water.  Put it back in the bottle, replace the pump cap and try sinking it again.

6.  When you are satisfied with your divers and would like to make it permanent, you can seal it by sealing the open end of the bulb.  This can be done with any waterproof glue, hot glue, or by melting the plastic stem slightly and squeezing it gently with small pliers.

To seal the bulb by melting, first make sure your bulb floats.  Once it is sealed, its starting buoyancy cannot be changed! Make sure there is no water in the neck by holding it upside down and tapping or squeezing it slightly.  Hold the neck about 1-2 inches above a candle flame until it becomes completely transparent (the change is very subtle).  Immediately remove the neck from above the flame and squeeze the end gently with pliers to seal.  Let cool.  Return your diver to the bottle with clean water and it will last for many years.

There are literally hundreds of experiments you can try!  For instance, try crumpling up a piece of aluminum foil into a small ball.  Place this in your bottle.  See if you can sink it by squeezing the bottle… how about pumping it?  Small packets of soy sauce have also been known to work!

Use more pipets and vary their densities.  Try numbering your divers and see if you can make them sink in order.  Note that your divers are not yet sealed, and so they can be adjusted as many times as you like (colored water will leak out of them until they are sealed).

Educational Innovations carries a full line of Cartesian diver materials, including Bob Becker’s DVD that demonstrates and discusses a plethora of fascinating diver designs.  Bob Becker, an award winning high school chemistry teacher, is a pioneer in the field of Cartesian divers.  This DVD includes DVD-ROM which contains additional resources such as project guides and templates.

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Posted by Tami O'Connor

Toroidal Vorticies

January 7, 2010

by: Ellen Lewis

A Toroidal Vortex is whirling air or liquid in the shape of a doughnut.  Vortices are created in nature by many things including dolphins, volcanoes, tornadoes, hurricanes, and whirlpools.  They can be created around the wings of an airplane, in the wake of a boat, or in a rocket blast.  Now you can make Toroidal Vortices in your classroom with the Zero Launcher and the Air Zooka.  Use these products to discuss friction, pressure, the Bernoulli Effect, or the Coanda Effect.

Activity 1: Simple Toroidal Vortices

Create a simple Toroidal Vortex with a droplet of food coloring and a tall glass of water.  Start by holding the dropper about 3 cm above the water’s surface.  Squeeze a single drop of food coloring straight down into the glass.  You will be amazed to see how the friction between the water and the food coloring will create the doughnut shaped rings!

See what happens when you drop the food coloring from different heights above the surface of the water.  How does this affect the size of the ring formed or the speed of the ring as it moves through the water?

When the drop of food coloring moves through the water, there is friction between the food coloring and the water.

The sides of the food coloring droplet get pushed upward as the food coloring continues to fall.

This causes material from the bottom of the droplet to flow to the top, which results in a hole in the middle.  A doughnut or Toroidal Vortex is formed.

This last figure shows a cross sectional picture of the Toroidal Vortex as it moves down through the water.

Activity 2: Fog Rings

Use the Zero Launcher to create Toroidal Vortices with fog fluid.

  1. Turn the Zero Launcher on, this will power the heating element needed to create the fog. The heating element vaporizes the glycerin, which condenses in the air.
  2. Push the pump button to fill the fog chamber with fog.
  3. Pull the firing lever back.  Releasing the firing lever will allow the plunger to strike the diaphragm and produce a fast moving pulse of air.  Once the fog passes through the opening of the chamber, the outside stationary air slows down the airflow of the fog, similar to how the water slowed down the droplet in Activity 1.
What happens when you move the launcher forward while you launch the fog rings?

What happens when you move the launcher sideways or up and down while you launch the fog rings?

What happens to the fog rings if you try to fan them?

Activity 3: Blow ‘Em Away

1. Grip the handle on the Air Zooka and aim at a target.

2. Grip the elastic air launcher with the other hand. Fully extend your arm and pull straight back (do not over pull).

3. Release the elastic air launcher to launch a powerful yet harmless ball of air!

4. Feel the Toroidal Vortices created by the Air Zooka!

Use the Air Zooka to blow out the birthday candles on your next birthday cake!

Use the Air Zooka instead of a softball to knock down Styrofoam cups in the carnival classic game with the cups stacked in a pyramid.  Visit Educational Innovations website www.teachersource.com to find Super! Wow! Neat! products to inspire your students!

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Posted by Tami O'Connor

The Amazing Drinking Bird

December 1, 2009

by Tami O’Connor

Invented in 1945 by Miles Sullivan, the “drinking bird” has been a favorite of science teachers in every classroom from kindergarten through college. This amazing device is made of two glass bulbs (one representing the head and the other representing the body) joined by a glass tube (representing the neck).  Between the two bulbs, attached to the glass tube, is a metal fulcrum upon which the bird pivots.  The air has been removed from this closed device, and the bottom ball is filled with a colored liquid that has a high vapor pressure (methylene chloride). The rest of the bird’s body and head is filled with the vapor form of methylene chloride.

The demonstration is set up such that a glass, filled to the top with water, is placed in front of the drinking bird. The glass should be the same height as the pivot point of the bird. The bird’s head should be moistened and then the bird should be given a gentle push to begin it oscillating along the pivot point.  Eventually, the bird appears to drink repeatedly, on its own.  So, how does that happen??

The top bulb (head) of the drinking bird is covered with felt. After the felt is moistened with water and the water begins to evaporate, the temperature in the head decreases. This drop in temperature causes some of the vapor inside the head to condense, causing the pressure inside the birds head to decrease. The decrease in pressure in the top bulb causes the liquid from the bottom to be forced upward from the base. As the liquid flows into the top bulb, the bird’s center of gravity moves upward causing the bird to tip forward, dipping its beak into the glass of water.

After the bird tips over and is horizontal, the bottom portion of the glass tube is no longer in the liquid. The glass tube, now 90 degrees to the surface allows the vapor from the bottom to travel to the top until the pressure is equalized.  At the same time, liquid in the column flows back to the bottom bulb. The weight of the bird is now primarily below the pivot point, so the bird returns to a vertical position.

The liquid in the bottom bulb is now exposed to the temperature of the ambient air, which is slightly higher than that of the bird’s head. This cycle continues as long as there is enough water in the glass to moisten the felt on the bird’s head. This cycle gives the appearance of a bird drinking!

SUGGESTED CLASSROOM ACTIVITIES

I) Classroom Discussion

Q. Is this an example of perpetual motion?

A. No. The cycle repeats itself only as long as the water evaporates from the head

Q. What is needed in order for the Drinking Bird to work?

A. A difference in temperature between the head and body.

II) Student Challenges

  1. Observe the operation of the Drinking Bird and explain how it works.
  2. Discover a way to make the Drinking Bird cycle faster.
  3. Predict what will happen if a fan blows air toward the Drinking Bird. Does it make a difference which direction the air blows?
  4. Predict the result of using warmer or cooler water in the glass.
  5. How long will the bird cycle without needing a refill of the water in the open container? Can you find a way of causing the bird to cycle longer?
  6. Is there a difference in the cycle rate on a humid day vs. a dry day? Can the bird be used to determine the relative humidity in the air?
  7. Predict the result of placing a small inverted aquarium over the bird. Does this cause the bird to cycle more or less? (Note: as soon as the water in this closed system reaches its vapor pressure, water from the felt can no longer evaporate and the bird stops.)
  8. Can you attach a thread to the bird so that it does useful work, e.g. lifting a small paper clip?

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Posted by Tami O'Connor

Chemistry of UV Detecting Beads

November 13, 2009

ronby: Ron Perkins

UV-sensitive beads contain pigments that change color when exposed to ultraviolet light from the sun or certain other UV sources. The electromagnetic radiation needed to affect change is between 360 and 300 nm in wavelength. This includes the high-energy part of UV Type A (400-320 nm) and the low energy part of UV Type B (320-280 nm). Long wave fluorescent type black lights work well; incandescent black lights and UV-C lamps will not change the color of the beads.

The dye molecules consist of two large, planar, conjugated systems that are orthogonal to one another. No resonance occurs between two orthogonal parts of a molecule. Imagine two planes at right angles to one another, connected by a carbon atom. When high energyuv651 UV light excites the central carbon atom, the two smaller planar conjugated parts form one large conjugated planar molecule. Initially neither of the two planar conjugated parts of the molecule is large enough to absorb visible light and the dye remains colorless. When excited with UV radiation, the resulting larger planar conjugated molecule absorbs certain wavelengths of visible light resulting in a color. The longer is the conjugated chain; the longer the wavelength of light absorbed by the molecule. By changing the size of the two conjugated sections of the molecule, different dye colors can be produced. Heat from the surroundings provides the activation energy needed to return the planar form of the molecule back to its lower energy orthogonal colorless structure.

Although UV light is needed to excite the molecule to form the high-energy planar structure, heat from the surroundings provides the activation energy to change the molecule back to its colorless structure. If colored beads are placed in liquid nitrogen, they will not have enough activation energy to return to the colorless form.

The UV detecting beads remain one of the least expensive qualitative UV detectors available today. They cycle back and forth thousands of times.

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Posted by Tami O'Connor

Ammonite,The Fibonacci Fossil!

November 12, 2009

brandtby: Sara Brandt

Ammonite was once thought to be the petrified remains of snakes! Modern science, however, tells us that these fascinating fossils are actually the remains of an ancient aquatic mollusk.  A mollusk is an invertebrate with a soft, unsegmented body.  The soft body of an ammonite was protected by a hard outer shell. The shells of ammonites ranged from an inch to nine feet! Each shell is divided into many different chambers. The walls of each chamber are called septa. The septa were penetrated by the ammonite’s siphuncle, a tube-like structure that allowed the ammonite to control the air pressure inside its shell. Ammonites were aquatic creatures, and being able to control the air pressure inside their shells meant being able to control their buoyancy.

What is the Fibonacci sequence? The Fibonacci sequence is a list of numbers where every number is the sum of the previous two. The Fibonacci sequence starts at 1 and grows infinitely:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55 …

To put this sequence into mathematical terms, each term Fn = Fn-1 + Fn-2. The Fibonacci sequence can be illustrated geometrically by drawing boxes. The first box should be 1×1, the second box 1×1, the third 2×2, the fourth 3×3, the fifth 5×5, the sixth 8×8, and so on. Each box should be adjacent to the boxes that come before it, forming a spiral of boxes. Have your students create their own Fibonacci squares – graph paper with small boxes works best.

What does ammonite have to do with Fibonacci? Ammonite shells are a naturally ammoniteoccurring example of the Fibonacci sequence. If you draw a quarter circle in each Fibonacci square, they connect to form an ever increasing spiral. Try to find the Fibonacci squares in your ammonite fossils – photocopy the fossil, then start at the very center by drawing two small boxes right next to each other. With Fibonaccimost fossils, the first boxes are .25 cm by .25 cm. Continue drawing boxes with Fibonacci dimensions. You’ll notice that the spiral of the shell always falls within the Fibonacci squares.

To further examine the concept of the Fibonacci number sequence in nature it is a worthwhile activity to have your students examine plants and flowers.  So many of them have leaf structures, petals, and stems that follow the series.  These spirals can be seen in everything from sunflowers to pine cones and even pineapples.

If your school doesn’t have access to ammonites, a field trip around the school grounds to identify the Fibonacci sequence in daisies, black-eyed susans, and seed heads would yield many oohs and aahs from your students.  The types of explorations are endless as examples of the Fibonacci sequence and the Golden Ratio are, indeed, endless!

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Posted by Tami O'Connor

Goldenrod Paper

October 1, 2009

ronby: Ron Perkins

Color changing goldenrod paper has been exciting students of all ages for decades to the wonders chemistry! Imagine the enthusiasm of the first student or teacher who spilled a few drops of ammonia on a piece of yellow paper and observed it turn bright red! One can only image them exclaiming: “Super, Wow, Neat!!!”

Place the paper in a solution of household baking soda and the paper turns red; immerse it in vinegar and the red turns back to yellow! This goldenrod paper is colored with a dye that is an acid/base indicator: red in base and yellow in acid. The paper is similar to litmus paper that is blue in base and red in acid.

Even though color changing, goldenrod paper is no longer being manufactured, Educational Innovations, Inc. still has a supply and the paper is being sold in 100 sheet packages, (#SM-925). This special paper was being manufactured until Junesm925 of 2008. At that time the process was changed to use a different dye that is more cost effective and better for the environment. Currently, paper of the same color, Galaxy Gold, is being offered by retail office supply stores, however, this paper uses a different dye and is not color changing.

Simple Activities With Goldenrod Paper

1. Write a “secret” message on the paper with paraffin or candle wax. The invisible message can be seen by spraying or wiping the paper with a weak basic solution e.g. ammonia (NH3 (aq)) or baking soda (NaHCO3). If you use ammonia solution, the message will disappear when the ammonia evaporates. If you use a baking soda solution, the message will remain.

2. Write a message on the paper using a cotton swab dipped into household ammonia. As the ammonia evaporates, the red message disappears.

3. Repeat Activity #2 using a cotton swab dipped into a solution of baking or washing soda. The message can be erased using vinegar (HAc) as “Yellowout .”

4. Use goldenrod paper to classify household products as acidic or basic. Solutions that turn yellow paper red are bases; solutions that turn red paper yellow are acids; and solutions that do not turn the color of either paper are considered “neutral.”

5. Tape a piece of yellow goldenrod paper to the board. Dip your hand into a shallow container of baking or washing soda and water. Then, when you press your hand against the paper, you will leave a “bloody” hand-print. Especially useful at Halloween. Compliments of Bob Becker 1985, Greenwich High School

6. Sponge the surface of a piece of goldenrod paper with a baking soda or washing soda solution and allow the wet, bright red paper to dry. Then, tape the paper to the board and press a hand that has been dipped into vinegar against the paper. The yellow hand-print will be the reverse or the “negative” of the result in activity #5. Complements of Carl Ahlers 2008, Australia

More Advanced Activities with Goldenrod Paper

7. Sponge a solution of baking soda or washing soda on a piece of goldenrod paper. Observe that the red color becomes gradually darker. Explain? Carl Ahlers has written: “Drying shifts the equilibrium in reaction 1 to the right as the H2CO3 is reduced due to the evolving of CO2 gas (reaction 2) (Le Chatelier). Subsequently more of the red Gol forms on drying. HGol (yellow) + HCO31- <—> Gol1- (red) + H2CO3 (aq) Reaction 1 H2CO3 (aq) <—> CO2 + H2O Reaction 2

8. Determine the equilibrium constant, the Ka, for this acid/base indicator. One way is to prepare a set of different pH solutions using a method of serial serial dilution on a spot plate or in small test tubes. Then, test to see at what pH the color change seems to occur for this indicator paper.

9. Make color-changing paper similar to goldenrod paper using household tumeric powder. Although tumeric is insoluble in water, in a workshop at Sacred Heart University, ca 1987, we discovered it was soluble in either ammonia or ethyl alcohol. White paper dipped in a solution of ammonia with dissolved tumeric will be dyed red which turns to yellow as the paper dries; dipped in a solution of tumeric and alcohol, the paper will remain yellow as it dries. When dry, test and observe how similar and how different the paper is from the color-changing goldenrod. Note: although this paper seems to react similar to color-changing goldenrod, the color fades much faster.

10. Prepare acid/base color changing paper using natural indicators: rose petals, purple cabbage, etc. Then determine the pKa of the paper.

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Posted by Tami O'Connor

Heat Sensitive Paper

September 11, 2009

ronby: Ron Perkins

A short time ago I received the following inquiry regarding our Heat Sensitive Paper. One of the joys of being the president of Educational Innovations is having the opportunity to answer questions like this.

Q: What chemical coats your Heat-Sensitive Periodic Tables that makes it change color? My chemistry class wants to know the chemistry of what is happening. Can you pleasehea300 help us.

A: Some of the characteristics of our heat sensitive periodic tables are easy to understand and some more challenging. The inks used provide color at lower temperatures and are colorless at higher temperatures. The change over temperature is called the “critical temperature.” Adding heat to the paper causes the paper to loose its color, an “endothermic” reaction. The reverse, going from colorless to colored, is an “exothermic” reaction and returns the heat.

To manufacture this paper, long rolls of white paper are unwound, coated on one side, dried, cut, and finally stacked into reams. This is done at a company that produces labels for cans. The paper is then printed with black ink to produce our periodic tables.

Educational Innovations, Inc. was one of the first companies to sellhea200
thermochromic paper and drinking cups, over 15 years ago. We followed up on an article about this new discovery in the NY Times. At that time the “Touch-It” paper used two colors of heat sensitive inks: blue and red – both turning colorless when heated. From those two heat
sensitive inks, five colors of paper could be manufactured: red paper
which turned colorless; blue paper which turned colorless: orange
paper which turned yellow; green paper which turned yellow; and purple
paper which turned colorless. For the orange and green paper, the
thermochromic inks were printed on yellow paper.

The complete chemistry of thermochromic, heat sensitive ink, involves micro-encapsulation techniques. Incidentally, you can increase the sensitivity of your periodic table by removing any absorbed moisture with a hair dryer or putting the paper through a copy machine.

I have found that kids of every age find this paper fascinating. Teachers use this paper to print newsletters home to parents, for special certificates or awards, and for printing diagrams or other papers the students should keep. They can even be laminated to use as bookmarks, hall passes, or as class syllabus.

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Posted by Tami O'Connor

Back To School Fun

September 8, 2009

tamiby: Tami O’Connor

Though I am no longer in a traditional classroom, the end of each August still fills me with that feeling of eager anticipation and yes, even a bit of anxiety…. Then I remember, I’m not going to be facing a room filled with bright new faces nor will I need to develop the plethora of creative lesson ideas necessary to engage and stimulate young minds. But still, I enjoy sharing some of the lessons that my students and I enjoyed.

One activity I used to teach the scientific method required the use of an old favorite; Sodium Polyacrylate. This is the chemical powder found in disposable baby diapers. I would start my lesson with a 3 Cup Monty game in which I used 3 opaque cups that were identical in every way except that two of the cups were empty and in the third I placed about 3 tablespoons of the water lock powder.

My shtick started with me talking about the importance of observation skills. I would explain the necessity of having a keen eye. Shortly after my speech I would pour about 1/2 of a cup of water into one of the empty cups. While encouraging my students to carefully watch the cup with the water in it, I would move the cups around fairly slowly, knowing they would be able to follow the water filled cup easily, until the three cups ended in a line across my desk.

When the motion stopped, I would ask the class to identify the “water” cup. When they did, I would pour the water from the “water” cup to the other empty cup and repeat, only this time I would move the cups a bit more quickly. Since I am admittedly not very fast, most of my students were able to identify the “water” cup on the next try.

I continued two or three more times complimenting my students’ observation skills as they identified the correct “water” cup each try. On the last try, I would pour the water from the “water” cup into the cup with the powder hidden in the bottom. As you can imagine, the water was quickly absorbed by the sodium polyacrylate and solidified leaving no liquid behind in the cup.gb6

On the final trial I moved the cups as quickly as I could trying to distract the students as much as possible as I shifted, bobbed, and weaved… I even stopped from time to time to point out the elusive leprechaun poking his head in the window, and while a few kids turned to look, I unfairly continued to move cups. Finally, when I sure I had fooled at least a few kids, I stopped.

With my three cups neatly lined across my desk, I would call on one student to identify the “water” cup. After pointing out the suspect cup, I flipped the chosen cup over to show there was no water in it. Try number two provided the students a 50-50 chance of identifying the “water” cup. Of course, one more wrong pick… Since I have already mentioned that I am fairly slow, chances were good that one of the chosen students had identified the correct “water” cup earlier, but because of the sodium polyacrylate, when I turned the cup upside down, the solid water remained stuck inside the cup.

There is always at least one student in the class who insists that the cup with the water in it has already been selected. I tend to call that student up to the front of the class to prove that their observation skills are the most astute by challenging them to stand under the last cup while I pour out whatever is inside it over their head. I build up the anticipation by having the guinea pig don a rain jacket…

While the class would cheer (and jeer) I would make quite a production of the cup over the brave (or foolish) student’s head being filled with water. As you already know, when I turned the final cup over, amid the oooooh’s and aaaaah’s, no water came out, and my student stayed dry. Imagine, three cups empty cups now, where at one point, at least one had water. There was no doubt, I had everyone’s attention

No matter what the grade level, this lesson is sure to generate interest. Now, everyone knows that you can have a terrific introduction, but the lesson has to have teeth in order for our students to learn. There are a number of activities you can launch into immediately following this introduction.

  • What is the ratio of water to powder that sodium polyacrylate will hold?
  • What are the chemical differences between the water loc and snow polymer?
  • Which baby diaper holds the most water?
  • Why does adding salt to the solid water reverse the effect of the absorption.

1 Comment | Chemistry, Elementary Level, Experiments, High School Level, Middle School Level | Tagged: , , , , , | Permalink
Posted by Tami O'Connor

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