Magic Sand. General Description. Program Objectives. Time Required

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1 Organization: MRSEC University of Wisconsin Contact person: Erin Hood Contact information: General Description Magic Sand With two different interactive activities we use the carnival/ circus theme to expose how nanotechnology has advanced common materials. We explain the principles and demonstrate the hydrophobic effects of magic sand with an enlarged model, and follow up the demonstration with an interactive activity that compares how magic sand and regular sand interact with water. We facilitate learning by letting participants have fun while observing the nano-properties at work. Program Objectives Expose how nanotechnology can improve the materials in our everyday lives. Visitors will learn that magic sand is afraid of water because it is covered with a nanoscale monolayer of oil-like molecules. Nano is both everyday and cutting edge. Nano means working at super small size scales to manipulate materials to exhibit new phenomena. Will nano affect you? Time Required Set-up Program Clean Up 5 minutes 10 minutes 5-10 minutes 1 March 20, 2007

2 Nanosurfaces Table of Contents GENERAL DESCRIPTION... 1 PROGRAM OBJECTIVES... 1 TIME REQUIRED... 1 TABLE OF CONTENTS... 2 BACKGROUND INFORMATION... 3 MATERIALS... 4 SET UP... 4 STEP 1:...ERROR! BOOKMARK NOT DEFINED. PROGRAM DELIVERY... 5 SAFETY:... 5 PROCEDURE AND DISCUSSION:... 5 TIPS AND TROUBLESHOOTING:... 6 GOING FURTHER...ERROR! BOOKMARK NOT DEFINED. CLEAN UP March 20, 2007

3 Background Information Everything is different at the nanoscale. Nanotechnology has begun entering products that we use everyday life, mostly in the form of surface treatments. Visitors may already be aware of stain-resistant Nano-Tex fabric, which exhibits hydrophobic (water-repellant or literally water-fearing ) properties. This activity explores magic sand. Hydrophobic sand, also known as magic sand, is an example of science on the nanoscale. Treatment of the surface of individual grains of sand results in a new type of sand that behaves very differently from regular beach sand. To understand how hydrophobic sand works, we first must understand some basic principles of water. Water is highly polar. Its molecules carry positive and negative charges that form strong hydrogen bonds. The bonds are so strong that non- polar substances that cannot form hydrogen bonds cannot mix with the water. Oil, for example, is non-polar. When it comes in contact with water it expands across water s surface area, but does not mix with it. Like attracts like; polar molecules attract other polar molecules, and non- polar molecules mix with other nonpolar molecules. Water either repels or completely encapsulates non- polar substances so it can continue to bond with itself. Molecules that water repels are called hydrophobic, or water- fearing. They are always non- polar and include greasy substances like oils, fats, or tar. Natural sand is not repelled by water; it is hydrophilic, or water- loving. It readily absorbs water, and immediately sinks when placed inside it. The surfaces of sand and water both carry positive and negative charges, and are therefore attracted to each other. Through the application of nanotechnology scientists have created a way to reverse these effects and make sand hydrophobic. Natural sand grains are exposed to a silicon compound, which results in the formation of a non-polar layer on the sand grains surfaces. This layer repels water from the surfaces of individual grains of sand. When magic sand is sprinkled on water s surface, water molecules prefer to bond with other water molecules and prevent the grains of magic sand from breaking through the surface until the layer of magic sand is thick enough. This same effect keeps magic sand dry. Water molecules will not attach to individual grains of magic sand or flow between them, thus not wetting them. Oil, however, has different chemical properties in water. Its non- polar nature status allows large quantities of it to be absorbed by magic, or hydrophobic, sand. 3 March 20, 2007

4 Scientists have found ways to take advantage of these hydrophobic properties. They were originally developed for use in cleaning up oil spills. The sand was expected to mix with petroleum floating on the water s surface and add enough weight to make it sink to the bottom. The petroleum could then be dredged and completely removed from the water. The large amounts of magic sand needed for this process proved too expensive for the time, but it remains a viable use for the future. Magic sand has also been used to protect electrical and telephone wires in extremely cold climates. The wires are buried underground for protection from the temperatures, which makes repairs difficult and labor intensive when the ground is frozen. To solve this problem electrical junction boxes are covered with a layer of magic sand that is then capped with a few inches of soil. When rainwater seeps into the ground the layer of sand prevents it from settling around the junction box and the shallow cap on top of the sand is easy to break through, thus making the wires easier to get to and simplifying the repair process. Materials Activity: Model: Set Up Regular sand Hydrophobic Magic sand 2 Cups- preferably clear Water Magnetic sand surface board Monolayer molecule spacers Magnetic water pieces Graphic poster Stands for model and graphic Time: 5-10 minutes Stock supply of regular sand and magic sand near clear glasses 4 March 20, 2007

5 Prop surface model in stands, with magnetic water pieces and sand monolayer nearby Display graphic Program Delivery Time: about 15 minutes Safety: Very safe Procedure and Discussion: Come one come all and see the difference nanotechnology brings Or do you know some sand is scared of water? So scared is doesn t want to touch it? Stop and look closely very, very closely and you can seek the answers to these amazing acts of wonder! Magic Sand Model: Explain the polarity of water and ask a volunteer to gently throw water molecule magnets onto the surface of magnetic board that represents regular sand. Explain how the water molecules attach because they are attracted to its surface. Then, add the pink monolayer to represent magic sand. Explain that we are working with a model and in reality the board represents one grain of sand and the monolayer is 1 nanometer thick. Ask a volunteer to gently throw the water molecule magnets onto this surface. They will roll off. Explain that they do not stick because the monolayer changes the polarity of the surface. Talk about the interaction of oil and water to reinforce the interaction of polar and non- polar molecules. Magic Sand Interactive: Compare magic and regular sand. Allow participants to touch so they can determine that color is thus far the only difference. Pour each sand type into a separate Erlenmeyer flask. Ask two volunteers to pour a measured amount of water from a graduated cylinder into the flask and gently swish it around so the water has an opportunity to mix with the sand. Cover the flask with cheesecloth and ask volunteers to pour as much of the water back into the cylinder as possible. Compare the amounts of water and explain how regular sand absorbed most of the water while the magic sand repelled all of it. Finally, pour some of the sand back into the original trays, and allow visitors to touch so they can see that the regular sand is wet while the magic sand is dry. 5 March 20, 2007

6 Tips and Troubleshooting: Water and sand have potential to be messy- have cleaning materials nearby Clean Up Time: 5-10 minutes Dry magic sand to reuse 6 March 20, 2007