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Science Behind the Bubbles
Bubbles, are quite simply, air trapped inside soap and water. Surface tension is caused by air pressure on both sides of the soapy film. Water alone has too much surface tension and is not very flexible. Soap is added to the water to make the film more flexible. That is why a soapy mixture that is too watery makes bubbles that quickly burst. Watery solutions also cause faster bubble bursts because water evaporates faster than soap.
Bubbles are always rounded in shape. The liquid skin of the bubble seeks to make the smallest possible shape while maintaining its surface tension. That shape is the sphere. It is possible to create other shapes, but only with a lot of patience and a lot of tools. Also, should one of these other shapes actually be formed, such as a cube, it tends to be rounded out on the sides.
When two bubbles join each other, they seek to minimize their surface area by creating a wall. Two bubbles that are the same size will end up with a wall that appears flat. If one bubble is larger than another, the smaller bubble will appear to bulge from the larger bubble. Put three or more together and the walls consistently meet at an angle of 120 degrees.
Bubbles also appear to change colors as they float through the air. White is the combination of all wavelengths of colors. When that white light hits the bubble, the soapy skin interferes with the light and removes wavelengths of color, depending on the thickness of the liquid skin. A bubble is thicker when it is first blown. As it becomes thinner, more wavelengths are removed, thus causing colors to change.
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Learning Questions about Bubbles
Find out how much your preschoolers know about bubbles by asking them questions.
- How are bubbles made?
- Of what are bubbles made?
- From where does the air come inside the bubbles?
- Can you blow bubbles just using water?
- What shape are bubbles?
- What color are bubbles?
- Do bubbles work better in cold or warm temperatures?
Record their comments and answers before allowing them to experiment with making bubbles. When they are finished making bubbles, try to ask them the questions again. Compare answers and then explain the science behind the bubbles that interests them.
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Experiments for Exploration
Let preschoolers explore bubbles by providing many opportunities. When they are outside, children can have traditional fun blowing bubbles through wands. Make your own wands by bending wire into different shapes to see if the shape of the wand affects the shape of the bubble. Set up a large tub of soapy water so that they can try other items such as hangers and string tied to a stick. Tie together a bunch of straws for multiple bubbles. Try straws of different lengths to see if that makes a difference. Let them experiment with other objects that they think may be able to create bubbles.
Practice catching bubbles. See if it is possible to catch bubbles by hand. Compare using a wet plate with a dry plate. Try to capture them in a bucket of water or in a jar. Catch them on wands, buckets, toys, or anything else that is available in the classroom or on the playground.
Have children experiment with making their own bubble solutions. Have them determine which kinds of soap work better and how much of each soap needs to be added before the solution works. See how glycerin affects the mixtures. Try using soap mixtures and immediately compare them to ones that have been sitting out all night.
Compare solutions of soap and water (with or without glycerin) to solutions of soap and another liquid, such as white vinegar. Try water mixed with different substances.
Think of other ways to make bubbles inside the classroom. Use a wire whisk or rotary beater to create bubbles from dish soap or grated soap flakes in a bowl of water. Add dish soap to a bowl of water and use a straw to blow bubbles in it.
For something a little different, blow bubbles onto a plate and put them in the freezer. Compare those to bubbles blown near a heated surface, such as a furnace or near a hair dryer. Try to make bubbles using different temperatures of water.
Try to create new colors of bubbles. Add food coloring or nontoxic paints to the bubble solution.
Ask children for their ideas on variations for science experiments using bubbles. You never know where their curiosity will lead!
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References and Resources
Brown, Sam Ed. Bubbles, Rainbows & Worms. Gryphon House, 2004.
"Bubbles." Exploratorium. http://www.exploratorium.edu/ronh/bubbles/bubbles.html
"Bubbles Theme: Bubbles Recipes." Step by Step Childcare. http://stepbystepcc.com/bubbles3.html
"Good Clean Fun". Family Fun. http://familyfun.go.com/playtime/good-clean-fun-701926/