1. Break up Into Groups of Two Or Three

Raindrop Raceway

Water sticks pretty well to itself but does not stick so well to other stuff. See this in action on your own Racedrop Raceway!

Materials

Cardboard Wax paper Tape Water Racedrop Racetrack Isopropyl alcohol

Viscosity The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal notion of "thickness". For example, honey has a much higher viscosity than water.

Directions

1. Break up into groups of two or three. 2. Announce that we want to find the best combination of a type of liquid and type of paper to use in order to race a drop of liquid across the paper. 3. Place a couple of drops of water on a piece of notebook paper and observe what happens. 4. Place a couple of drops of isopropyl alcohol on a piece of notebook paper and observe what happens 5. Place a couple of drops of water on a piece of waxed paper and observe what happens. 6. Place a couple of drops of isopropyl alcohol on a piece of waxed paper and observe. 7. Which combination do you think would work best? (The water-wax paper combination will be the best) 8. Print out the Racedrop Raceway. Place the Raceway on a piece of cardboard and tape it down securely. 9. Tape a piece of wax paper over the raceway. You should be able to see the raceway clearly through the wax paper 10. Drop a few drops of water onto the starting point of the raceway. 11. Tilt and move the board to make your race drop. Ask your partners to time you to see how fast you can get to the finish line. 12. Try this multiple times and record your results. 13. After everyone has had a turn, have a class tournament to see who can do it the quickest in the class.

Questions to ask and think about…

1. Why did you use wax paper instead of just putting the drop directly on the racetrack? 2. Why do drops of water combine with themselves but not with the wax paper? 3. Can you think of any other place where water “beads up” like it does on wax paper?

Where's the Chemistry? Something about water that you may have noticed is the way in which it sticks to itself. In fact, if you bring two drops of water close together, they will happily join each other to make one bigger drop. But there are some substances that water will not stick to, such as those made from oil or wax. This is why the water sticks to itself to make a race drop, but does not stick to the wax paper track.

Note: If there is extra time have the children design their own race track. Test it out with the wax paper. Trade tracks and try out your classmates!