## Bubble Basics

November 12, 2010

by: Michelle Bertke and Melanie Bunda

Bubbles are always a fun and interesting activity for kids of all ages.  However, bubbles are not only fun, they are also an excellent teaching tool for some abstract concepts such as air density, dissolved gasses, and air pressure.  Below is a collection of bubbly activities that highlight each of these topics. Educational Innovations offers a full line of wonderful bubble products!

Gravity Defying Bubbles

Different gasses have different densities.  The air around us is mostly nitrogen (N2) and oxygen (O2), which are both lighter than carbon dioxide (CO2).  When a heavy gas, such as CO2 is placed in a tank, it will sink to the bottom without mixing.  This can be achieved by placing a few blocks of dry ice in a large fish tank or clear plastic bin covered loosely with a lid and allowing them to sublime.  This will take several minutes. Always use caution when handling dry ice by using proper gloves and safety goggles. Once full, blow bubbles over the surface of the tank.  When the bubbles reach the interface of the two gasses, they will float.  If you fill the tank with CO2 unnoticed, have the kids speculate as to why they think the bubbles didn’t reach the bottom, and what might be in the tank.  An alternative is to fill a balloon with CO2 by filling it with baking soda (or an alka seltzer tablet) and placing it over the opening of a bottle filled with vinegar (or water).  Lift the balloon so the contents spill into the bottle and react with the liquid, allow the balloon to fill from the reaction, twist and remove.  Use it to blow bubbles.  Compare these bubbles to those blown with regular air (use a fan, not your breath for best results).  Have students compare the two bubbles.  Which one falls faster? Which one floats longer?

Dancing Raisins

All kids will know that soda pop is fizzy, but they may not know where all those little bubbles come from.  This demonstration will highlight the dissolved gasses in soda.  Fill a glass with a clear soda.  As you pour in the soda (pour gently down the side to retain maximum fizziness in the liquid), you will see bubbles forming from the bottom and the sides of the glass.  Ask the students why they think that bubbles only form in these places.  Next, take a few raisins and drop them into the soda (you may need to break the raisins into smaller pieces).  You will notice that bubbles immediately begin to form in the crevices of the raisins.  As more bubbles collect on a raisin, it will begin to rise.  When it reaches the top, the bubbles on the outside will escape into the air and this will cause the raisins to sink, and the cycle to begin again.  Pretty soon you will have a glass of dancing raisins.  This should raise discussion about dissolved gasses and buoyancy.  Students can experiment with different sodas and different materials to see what may cause more or less bubbles to come out of solution.

Mentos and Soda

Another classic example of dissolved gasses is the Mentos and soda demonstration.  This demonstration can be done by anyone with just a two liter bottle of soda and a pack of original Mentos.  Make sure you are in an area which can get messy and sticky.  Simply open the soda and the pack of Mentos.  (Fashion a Mentos delivery apparatus out of a rolled up piece of paper to prevent getting sprayed.)  Quickly drop the Mentos into the soda all at once and immediately step back.  The ensuing fountain will go high into the air and cause widespread excitement.  The same tests can be done as were mentioned in the raisins: what kind of soda makes the highest fountain? Do different types of Mentos cause differences in the height of the fountain?

Square Bubbles

All bubbles are round.  Or are they?  A free flying bubble, no matter what shape wand produced it, will always be round.  Why is this?  When you blow a bubble, the soap solution stretches as the air flows into it, and the air pushes equally on all sides of the bubble.  This creates a perfectly spherical bubble with equal pressure on all sides.  But what happens when the wand is a three dimensional cube?  Make a cube frame out of pipe cleaners.  (Make sure to attach a handle to hold on to.)  Fill a tall beaker with soap solution and dip the cube into it, fully submerging it.  Remove the cube from the container, and you will see a square “bubble” stretched between the sides of the form.   If you blow on one side of the cube structure, the sides will collapse in on each other and come together at a point.  Now take a straw and gently blow into the center of that point.  If you get it just right, you can form a cubic bubble in a bubble!  Give the students several pipe cleaners and allow them to create their own 3D bubble wands.  See what other kinds of bubbles they can form.

Any way you look at it, either from a scientific point of view or as a kid on a sunny day, bubbles are a fascinating activity to be shared by all.  Next time you are strapped for something to do, just whip up a batch of bubble solution and let your imagination run wild.

## What is That Stuff?

November 3, 2010

by: Elaine Kotler

I created a lab using the Instant Snow Polymer (Sodium Polyacrylate) from Educational Innovations that I use in my 8th grade Physical Science Class as well as Summer School Programs that I teach for grades 4-9.  This lesson incorporates concepts of Conservation of Mass, Properties of Matter, Metric Measurement and Conversion, and Observation Skills.  The lab, as I give it to the students, is listed below.

Each student receives an empty baggie to be used for comparison, a baggie containing 12 grams of Instant Snow Polymer, use of a balance and a graduated cylinder.

I have already explained the Law of Conservation of Mass, and Density (they need to remember that the density of water is 1 g/ml, or look it up) prior to introducing this lab activity.  However, they do not know the terms exothermic, endothermic, hydrophobic or hydrophilic.  My students are allowed to look them up, but unless they make careful observations as they are conducting the experiment, they won’t be able to answer the questions later.

The final question “What is That Stuff?” garners some interesting answers. Some recognize a use for it as snow for ski slopes; others have suggested material for ice packs.  One suggestion was to use the powder to help clean up and absorb spills.

It is wonderful to see the faces of the students as they are in awe of what is occurring in the baggie.  I allow the students to color the water, if they so desire.  One year I did the lab on Saint Patrick’s Day.  Guess what color most students chose?

Elaine Kotler
Saint Paul School, Kensington, CT
Summer Options for Kids, West Hartford, CT
Kids on Campus, Middlesex Community College, Middletown, CT

What is That Stuff?

1.           Record mass of the empty baggie as given by Miss K (A)

2.          Without opening the baggie, use a scale to measure the mass of the bag with the contents in grams (B). Record data.

3.          Calculate the mass of original contents by subtracting the mass of the empty baggie from the mass of the baggie with the original contents.  Record data (C).

4.          Feel the contents of the baggie through the baggie and think about how it feels temperature–wise.

5.          Using a graduated cylinder, measure 160 ml of water. Record volume of water (D).

6.          Calculate the mass of the water. DO NOT MEASURE!!  Record data (E)

7.          Open baggie and add water to the powder.

8.          Immediately zip the bag closed.

9.          Shake the bag to mix the powder and water and watch what happens.  DO NOT OPEN THE BAGGIE.

10.       Without opening the baggie, take the mass of the baggie and its contents (F).  Record data.

11.        Calculate the mass of new contents by subtracting the mass of the baggie from the mass of the baggie and the new contents.  Record data (G).

12.       Feel the contents of the baggie through the baggie and think about how it feels temperature–wise.  Make careful observations.

13.       Add your measured mass for the original contents (C) and the calculated mass of the water (E).  Record data (H).

14.       You may now open the bag and play with the material.  It is non-toxic, however DO NOT PUT IN MOUTH.

15.        Clean up.

### Student Sheet

You must look up any terms you are unfamiliar with that are used in this handout.

Measurements and Calculations 10 points

A = mass of baggie (g) ____

B = mass of baggie and original contents (g) ____

C= mass of original contents (g) B – A ____

D = volume of water (ml) ____

E = mass of water (g) ____

F = mass of baggie and new contents (g) ____

G = mass of new contents (g) F – A ____

H = C + E (g) ____

What is That Stuff?

Questions

1.       Explain why you needed to measure the mass of the baggie during the experiment. (15)

2.      Explain how you arrived at your answer for E, since the mass of the water was not measured. (15)

3.      Is your answer to G the same as your answer to H (± 3 g for margin of error)?  Explain why or why not. (15)

4.      Is this reaction exothermic or endothermic?  Explain. (15)

5.      Is the powder hydrophilic or hydrophobic?  Explain. (15)

6.      And, finally, what is that stuff?  Describe it, give it a name and describe one use for that stuff. (15)

NAME _________________  Score ________ out of 100

## Using Gigantic Growing Spheres to Illustrate an Aspect of Rainbow Formation

November 1, 2010

by: Gordon R. Gore

BIG Little Science Centre

Educational Innovations has a new product called Gigantic Growing Spheres (Catalogue #GB-760) which physics teachers might find useful for illustrating internal reflection. These are a very large version (about 6 cm) of the Growing Spheres (also called Jelly Balls) discussed in earlier issues of BIGScience*.

Basic Equipment Needed

1 green* laser pointer (* works much better than red)

1 fully grown ‘Giant Growing Sphere’ (about 6 cm diameter)  Educational Innovations #GB-760)

The growing spheres, made of polyacrylamide polymer, are delivered in a plastic envelope, about 60 to a bag. They start at about 1 cm diameter, and after soaking in water for a day or two, reach a diameter of about 6 cm.

One use for these giant clear spheres, which are mostly water, is to illustrate internal reflection in a ‘drop’ of water, as in a cloud. A green laser pointer works very well, because of its brightness. The photo (above) shows what happens. Of course, a rainbow is the result of refraction, internal reflection and dispersion of all the wavelengths of sunlight by countless water droplets, but this is a useful simulation of what happens to one wavelength (colour) of light. It is possible to obtain a crude spectrum (rainbow) with the growing sphere if ‘white light’ from a ray box with one slit is aimed at the sphere. (Experiment to find the best incident angle.)

*Previous articles describing ways to use Growing Spheres (Jelly Balls) are in Volumes 142, 143 and 144 of BIGScience.

The BIG Little Science Centre was started in February 2000 by Gordon R. Gore, a retired science teacher who has dedicated his life to teaching science in an interactive environment. The Centre currently operates out of four classrooms leased from School District 73 at Bert Edwards Science and Technology School, 711 Windsor Avenue Kamloops BC, Canada.