How to Make Waterproof Sand
Waterproof, or hydrophobic sand, is sand that is afraid of water. You may have seen sand sold in toy stores called ‘Magic Sand’ and when you put it into water it never gets wet! Well, here is a fun and easy science activity that show you how to make you own Magic Sand at home.
WHAT YOU NEED: safety glasses, sand (colored crafting sand or sand from a pet store work really well), metal cake pan, oven, Scotch Guard.
WHAT TO DO:
- Spread a cup of sand onto a metal cake pan, making an even layer of sand.
- Place the sand into the oven and set it at 200 degrees Fahrenheit for 1 hour to remove any moisture still contained in the sand.
- Allow the sand to cool completely until it reaches room temperature.
- With safety glasses and the assistance of an adult, spray the sand with an even coat of Scotch Guard. Make sure your work area is covered with old newspaper or some protective covering.
- Allow any volatile gases to evaporate off the sand by shaking the sand occasionally for 10-15 minutes. Allow to dry completely (approximately one hour). When you’re done, you’ve made your very own Hydrophobic Sand!
- Slowly pour the Hydrophobic Sand into water and observe it’s behavior!
WHAT HAPPENS: When the sand is poured in to the water, it makes worm shapes. When the sand is taken out, it is completely dry.
WHY IT WORKS: Hydrophobic sand is sand that repels water. There are many common materials in our world that are hydrophobic. Oils, fats, greasy materials, and many leaves are all hydrophobic and are nearly impossible to wet. Their molecular structure resists attraction to the water molecule. Chemists have been able to utilize the behaviors of hydrophobic molecules to make synthetic hydrophobic compounds that we find in water proofing sprays. These sprays are used to water proof our outdoor wear such as boots or coats. They’re also put onto our carpets and upholstery to make spills easier to clean up. Normally these materials (boots, coats, carpets, upholstery, sand, etc.) have an attraction to water . These substances are hydrophilic, meaning they “love” water. The spray coats these materials with hydrophobic molecules making that barrier between water.