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Best Wand for Big Bubbles

Summary

Active Time
30-45 minutes
Total Project Time
30-45 minutes
Key Concepts
Surface tension, water
Credits
Megan Arnett, PhD, Science Buddies
Sabine De Brabandere, PhD, Science Buddies
Large bubbles float in the air

Introduction

Have you ever tried to blow a bubble, and no matter how hard you try, the bubble just will not form? Why does this happen? Why do bubbles form at all, and why is it harder to blow bubbles sometimes? In this activity, we will explore the limits of how big our bubbles can get!

This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Materials

  • Two dowel rods (at least ½" diameter works best.)
  • Two screw eyes (a closed loop with a threaded base) that can screw onto the dowel rods
  • Yarn or baker's twine (at least 18 feet or 6 meters)
  • A washer
  • Bubble solution (Optional make-your-own bubble solution ingredients are listed below.)
  • A bucket or large container to hold bubble solution
  • Outdoor area with space to run!
  • An adult helper
  • One or two measuring tapes (a total length of at least 3 meters)
  • Scissors
Bubble Solution (Makes approximately 1/2 gallon.)
  • Eight cups of water (1/2 gallon or about 2 liters)
  • Half cup of liquid dish soap (blue Dawn works well.)
  • One tablespoon glycerin
  • One tablespoon baking powder

Prep Work

  1. This activity could get a little messy. Everything should be done outside.
  2. Pour the bubble solution into your container. If you are making your own bubble solution, pour all ingredients into your container and gently stir to combine. Try to avoid creating a sudsy foam on the surface of the solution.
  3. Ask your adult helper to help you attach a screw eye to one end of each rod.

Instructions

  1. Cut a three-foot (or one-meter) length of twine and thread it through one washer and each screw eye, making a loop. Tie the ends of the twine together (the knot can be anywhere). Screw each screw eye on a different dowel rod. This is your bubble wand!

  2. Set your bubble solution container in an open area. Place your measuring tape on the ground, starting at your container and extending at least 10 feet (3 meters) against the direction the wind is blowing.

    A measuring tape stretched out away from a container with an arrow representing the direction of the wind pointing towards the container.
  3. Hold your rods on the ends without the screw eyes. Gently touch the two screw eyes together, and completely submerge the yarn in the bubble solution.

  4. Gently lift your wand from the bubble solution. Separate the ends of the rods to open the yarn loop.
  5. Hold the wand away from your body and slowly walk along the measuring tape into the wind.
    Think about:
    How big a bubble do you think you will be able to create?
  6. Have your helper measure the length of the bubble you create! Try it at least five times, and remember the longest.
  7. Cut the twine and remove it from the wand. Save the washer!
  8. Cut a six-foot (or two-meter) length of twine, and thread it through one washer and each screw eye, making a loop. Tie the end of the twine together (the knot can be anywhere). This is your new bubble wand!
    Think about:
    Do you think these bubbles will be easier or more difficult to form?
  9. Repeat steps 3–6 using the bigger wand. Remember the longest bubble you can create with the six-foot twine.
  10. Cut the twine and remove it from the wand. Save the washer!
  11. Cut a nine-foot (or three-meter) length of twine and use it to make a new bubble wand.
    Think about:
    Do you think you will be able to create bubbles with the nine-foot wand? If so, do you think this bigger bubble wand will make it easier or more difficult to form bubbles? Do you think it might be able to create larger bubbles?
  12. Have your helper assist you while you repeat steps 4–6, with each of you holding a wand. Measure the bubbles you create and remember the longest one created with the nine-foot twine.
    Think about:
    Which wand allowed you to create the largest bubbles? Why would this be the case?

Cleanup

Pour leftover soap mixture down the drain.

What Happened?

You probably created some of the biggest bubbles possible, with just a string and some patience! You may have found that it was easier to create the long bubbles with the shorter twine. As the twine got longer (especially at nine feet), it may have been more difficult to form big bubbles.

The bubble solution mixture that makes up a bubble's surface is composed of three very thin layers: soap, water, and another layer of soap. This is called a soap film. The water layer is what holds the bubble together. When the water between the soap layers evaporates, the bubble pops. The glycerin in the recipe thickens the walls of soap, and as such, makes it harder for water to evaporate. It helps create stronger, bigger, and longer-lasting bubbles.

At a certain point, however, bubbles get too big to hold together. Larger bubbles have their own weight to support. Imagine building a tunnel with LEGO® bricks. You can make a very long tunnel with a small diameter, but if you try to build a tunnel wide enough for an adult to walk through, it will have trouble supporting its weight. This is similar to what you experienced with the wand with longer twine. The body of the bubble was much larger, and therefore much more fragile.

Digging Deeper

Bubbles rely on surface tension to hold together. Water is made up of tiny particles called water molecules. Just like magnets can line up with and attach to other magnets, water molecules can line up with one another and attach by forming temporary hydrogen bonds. These bonds allow a water surface to act like an elastic membrane— an effect that scientists call surface tension. Drops of water on a piece of wax paper or other hydrophobic (water-repelling) material show surface tension in action. Instead of spreading or flattening, the water forms small, spherical droplets on the material (see figure). The water droplets can hold their shape because the water molecules are more attracted to one another than they are to the material. The strength of that attraction holds the water droplet together.

Three different sized water droplets rest side-by-side on a flat surface

The surface tension of water is so strong that it prevents us from blowing bubbles from just water. Adding soap or detergent lowers the water's surface tension, allowing the surface to stretch and bubbles to form. It does this by creating space between the water molecules, which decreases the strength of their attraction to one another. If you think again about magnets, when two are very close to each other, the pull between them is much stronger than when there is more space between them. Decreasing the strength of the attraction between water molecules lowers the surface tension of the bubble solution, allowing bubbles to form!

Although soap makes it possible to blow bubbles, it is still the surface tension of water that holds the bubble together. When the water evaporates, the bubble bursts. To make bigger and stronger bubbles, we need to prevent the water from evaporating. Adding glycerin to the soap solution does the trick by thickening the walls of soap.

At a certain point, bubbles get too big to hold together. This is because larger bubbles have a larger surface area, which means more places for external forces, such as air pressure and gravity, to have an effect. In addition, the larger bubbles have their own weight to support. For these reasons, large bubbles are much more fragile than small bubbles.

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For Further Exploration

  • What kind of bubbles can you make with a shorter wand?
  • What is the largest bubble you can create than will float freely? What shape does the bubble take once it leaves the wand? Why would this be?
  • Find the best bubble solution. Try removing the glycerin or the baking powder. How do these ingredients affect the bubbles you create? What happens if you double the amount of soap, glycerin, or baking powder?
  • Let the bubble solution sit overnight, then retry this activity. Test to see if you get bigger bubbles!

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