January 14, 2013
We Water Molecules Stick Together! | Surface Tension Demonstrations
by: Tami O’Connor
I am a believer that observing discrepant events burns concepts into students’ memories far longer than simply reading the facts of the lesson from a text book. A few years ago I was designing a unit on surface tension. Because so many awesome hands-on activities deal with this topic, my greatest problem was picking and choosing! In this blog, I will describe one of my students’ favorite surface tension demonstrations. It teaches about surface tension and capillary action.
Materials (per student):
- 2 – plastic cups (I prefer Solo brand)
- Electrical tape
- 18 inches of white yarn
- Food coloring
Cut 2 pieces of electrical tape (1 inch each). Using the tape, affix the end of the yarn to the inside bottom of one of the cups. With the other end of the yarn, repeat with the second cup. Put as much yarn as will fit into one of the cups, and add water until the cup is about half full. Holding the cups close together, pour the water from one cup to the other allowing the yarn to flow with the water. When the yarn is thoroughly saturated you are ready to begin. Read the rest of this entry »
February 24, 2010
by: Ron Perkins
Who knew that a single coin could be used for so many classroom science activities! You can demonstrate concepts such as surface tension, buoyancy, and even eddy currents with Japanese yen coins!
Surface Tension: Even though aluminum has a density of 2.7 gm/cm3, and the density of water is 1 g/cm3, aluminum yen coins can float on the surface of the water!
Surface tension is a physical property of water. It is caused by cohesion, which is the attraction of like molecules. Water molecules are made up of two hydrogen atoms and one oxygen atom. The “stickiness” of water is caused by hydrogen bonding. This hydrogen bonding pulls the water molecules towards one another and forms a sort of “skin” on the surface of the water.
Japanese Yen Coins Experiment 1:
Using a bent paper clip or a plastic fork, gently lower the flat side of the coin onto the surface of a pan or cup of water and remove the clip or fork. The coin should rest on the surface of the water. Read the rest of this entry »