National Chemistry Week Experiments: Bubbles! Every month, Dow’s “On Site” television program features a “science short” that links the chemicals we manufacture here at Dow with the chemistry and science behind them. We also work to show where and how some of these products are used in everyday life. Hosted by Dow scientist Mark Bernius, the segment helps demystify what goes on behind the fence here at Dow. Dow Michigan Operations is anxious to promote a wider understanding of science and chemistry for students and teachers and our other neighbors who are interested in what goes on behind the fence here at Dow and the practical ways Dow products positively affect every life. For National Chemistry Week, 2005, we are introducing the video segments from the monthly television show with accompanying pdf documents that have the experiments on them for you to do at home or in the classroom. All of these materials are offered to the public at no charge and are intended for reference only. All of these materials are offered to the public at no charge and are intended for reference only. Note: All referenced experiments should be done with adult supervision since some require the use of simple household tools, such as scissors and knives, and some could make a mess. Therefore, if you’re under the age of 18, be sure a parent or guardian is present. Experiment: Bubbles, Surface Tension and SARAN Dow manufactures a plastic material you find in every store to wrap your food. SARAN Wrap is known as a barrier film. The barrier is created by the plastic to keep air and bacteria off of food products, preserving their freshness. One of the secrets to manufacturing SARAN involves bubbles. Quantities of liquid plastic are blown into a big bubble to make the flat sheets of food wrap you use all the time. As a scientist, you can do something at home, in the classroom or your schools lab that engineers and scientists at Dow are doing to help preserve food every day; make bubbles. What Are Bubbles? Surface tension at the gas and liquid boundary (known as an interface) is caused by the tendency of liquids to stay away from gas. The attraction of the liquid molecules to themselves forces spheres of the liquid or bubbles to form which minimize the amount of surface area for a given volume and minimize the number of liquid molecules which must contact the air. The surface tension of the bubbles surface keeps the air trapped inside. The formation of any gas bubble demonstrates the pressure inside the bubble as greater than the pressure outside. The tires on your bicycle are a good example of this type of bubble. The pressure inside the tire is greater than the pressure on the outside and your tire stays inflated, same as bubbles.
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Materials Needed Dawn dishwashing liquid One gallon of water in a bucket Glycerin Heavy wire Plastic building toys Conduct the Bubble Experiment 1. To make the best bubble solutions add 1 part soap and ½ part glycerin to 8 parts of water. So if you have 8 cups of water, add 1 cup of liquid soap and ½ a cup of glycerin. 2. Using the building toy components, build a cube. 3. Using the wire, make a pyramid. 4. Make other shapes with the wires or building toys. 5. Dip your shapes into your bubble solution. 6. Slowly draw your shapes out of the solution. 7. Write down your observations with each shape. 8. You can experiment with different ratios of soap, water and glycerin to see how to make the best solution, though we think the one we have is best! 9. Imagine you are scientists at Dow and you are working with plastic instead of soapy water. What could you build with bubbles and thin films that you could not build with other materials? ###
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