Quick and Easy Bubble Experiments to Share with Your Kids!
by Aurora Lipper
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If you pour a few droplets of water onto a sweater or fabric, you'll notice
the water will just sit there on the surface in a ball (or oval, if the drop
is large enough). If you touch the ball of water with a soapy finger, the ball
disappears into the fibers of the fabric! What happened?
Soap makes water "wetter" by breaking down the water's surface tension by
about two-thirds. The force that keeps the water droplet in a sphere shape
is called surface tension. It's the reason you can fill a cup of water past
the brim without it spilling over. Water becomes "wetter" because without
soap, it can't get into the fibers of your clothes to get them clean. That's
why you need soap in the washing machine.
Soap also makes water stretchy. If you've ever tried making bubbles with your
mouth just using spit, you know that you can't get the larger, fist-sized
spit-bubbles to form completely and detach to float away in the air. Water
by itself has too much surface tension, too many forces holding the molecules
together. When you add soap to it, they relax a bit and stretch out. Soap
makes water stretch and form into a bubble.
The soap molecule looks a lot like a snake -- it's a long chain that has two
very different ends. The head of the snake loves water, and the tail end loves
dirt. When the soap molecule find a dirt particle, it will wrap its tail
around the dirt and hold it there.
To make the best bubbles, you'll first need to make the best bubble solution.
Gently mix together 12 cups cold water in a shallow tub with one cup green
Dawn (or clear Ivory) dish soap. If it’s a hot dry day, add a few tablespoons
of glycerin. (Glycerin can be found at the drug store.) You can add all sorts
of things to find the perfect soap solution: lemon juice, corn syrup, maple
syrup, glycerin... to name a few. Each will add its own properties to the
bubble solution. (When I teach this class, I have buckets of each variation
along with plain dish soap and water so we can compare.)
The absolute best time to make gigantic bubbles is on an overcast day, right
after it rains. Bubbles have a thin cell wall that evaporates quickly in direct
sun, especially on a low-humidity day. The glycerin adds moisture and deters
this rapid thinning of the bubble’s cell wall.
Zillions of Tiny Bubbles can be made with strawberry baskets. Simply dip the
basket into the bubble solution and twirl around. You can also use plastic
six-pack soda can holders.
Trumpet Bubbles are created by using a modified a water bottle. Cut off the
bottom of the bottle, dip the large end in the soap solution, put the small
end to your lips and blow. You can separate the bubble away from the trumpet
by rolling the large end up and away from your bubble.
Bubble Castles are built with a straw and a plate. First, spread the bubble
solution all over a smooth surface (such as a clean cookie sheet, plate, or
table top). Dip one end of a straw in the bubble solution and blow bubbles
all over the surface. Make larger domes with smaller ones inside. Notice the
bubble changes shape and size when it connects with another.
Stretch and Squish! Get one hand-sized bubble in each hand. Slap them together
(so they join, not pop!). What if you join them together s l o w l y?
Light Show is one of the favorites when I teach this class. Find a BIG
flashlight and stand it on end (or use a thin one with three clothespins). Rub
soap solution all other the bottom of an uncolored plastic lid (like from a
coffee can). Balance the lid, soapy side up, on the flashlight (or on the
spring-type clothespins). Blow a hemisphere bubble on top of the lid. Find
a dark room, turn on the flashlight, and blow gently along the side of the
bubble and watch the colors swirl.
Weird Shapes are the simplest way to show how soap makes water stretchy. Dip
a rubber band completely in the soap solution and pull it up. Stretch the
rubber band using your fingers. Twist and tweak into all sorts of shapes.
Note that the bubble always finds a way of filling the shape with the minimum
amount of surface area. Make a Moebius Bubble by cutting open a thick rubber
band or 1/2" thick ribbon, give one end a half-twist, and reattach it together.
Polygon Shapes allow you to make square and tetrahedral bubbles. Create
different 3D shapes by bending pipe cleaners made into cubes, tetrahedrons,
or whatever you wish. Alternatively you can use straws threaded onto string
made into 3D triangular shapes. Notice how the film always finds its minimum
surface area. Can you make square bubbles?
Gigantic Bubbles - Using the straws and string, thread two straws on three feet
of string and tie off. Grasp one straw in each hand and dip in soap solution.
Use a gentle wind as you walk to make BIG bubbles. Find air thermals (warm
pockets of air) to take your bubbles up, up, UP!
Really, Really, Really Big Bubbles - Gather together a 1/2” x 36” wooden
dowel, one eye-screw, 7-8’ lightweight chain, and a large nut that slides
easily over the dowel. Pre-drill a hole for the eye-screw at the end of the
dowel. Slide the nut down along the length of the dowel. Attach one end of
the chain (using pliers) to the eye-screw, then to the bolt (about 18” away),
and then drape about 5-6’ before attaching the end back to the eye-screw,
making a large ring of chain that can be opened and closed with the sliding
action of the bolt. Dip the bubble wand into soap solution with the ring
closed, raise it up out of the bucket, open the ring, walk a few feet until
a large bubble forms, then close the ring. (You can make a lighter-weight
version by substituting crocheted lace for the chain and a lighter ring for
the weight.)
Kid-In-A-Bubble - In a child's plastic swimming pool, pour your best bubble
solution. Lay a hula hoop down, making sure there is enough bubble solution
to just cover the hoop. Have your child stand in the pool (use a stool if you
don't want to get your feet wet), and lift the hoop! For a more permanent
project, use an old car tire sliced in half lengthwise (the hard way) to hold
the bubble solution.
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Aurora Lipper has been teaching science to kids for over 10 years. She is also
a mechanical engineer, university instructor, pilot, astronomer, a real live
rocket scientist (You should see the lab in her basement!) and a mom. She has
inspired thousands of kids with the fun and magic of science through her live
and online classes and materials at SuperChargedScience.com.
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