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Activity 1.1
Water Can Defy Gravity...Really!
In this simple demonstration, you will see how water can do what other liquids, such as vegetable oil, can’t.

What You Need:

  • Some wax paper
  • Water, vegetable oil, and small amount of liquid dish or hand soap
  • Eye droppers

What To Do:

  1. Place a drop of water on a smooth sheet of wax paper. Note how the drop remains domelike in shape.
  2. Now place a drop of vegetable oil on wax paper. What shape does the oil drop take?
  3. Next, place a small amount of liquid dish soap in some water and, using a dropper, create another drop of soapy water onto the wax paper. How does this drop compare with the other two drops?

What's Going On:

The water is demonstrating a phenomenon known as cohesion. Cohesion is defined as molecules sticking to each other, much like magnets. It is this stickiness of water that results in surface tension, a phenomenon in which water has what seems to be a skin on which water striders and other small insects can walk. That water is very sticky and can apparently defy gravity is due, in part, to the unusual shape of its molecules. Much like cheerleaders forming human pyramids, the water molecules, clinging to each other, defy gravity. Oil lacks the cohesive properties of water, so when placed on wax paper, the resultant drop tends to become quite flat. By adding soap to the water, the resultant drop too is somewhat flat. That’s because the soap helps to breakdown the cohesive properties of water, much like what happens when those cheerleaders stop holding onto each other and they tumble apart.

Take It A Bit Further:

Idea One:
See how many drops of water, oil, and soapy water can be placed on the surface of the separate pennies (or, if you really have nothing to do, use quarters!) before the liquids spill over the lip of each penny.

Now if you really want to do some real science in this experiment, you should repeat it a number of times (say about 10 times), then take an average of your results. The average number of drops for each liquid on the penny would then be plotted on a graph. You may think this is a waste of time, but it’s the only way to make certain that the difference you observed between the liquids is real, or not some one-time fluke. Prepare a bar graph that depicts the averages of your result for each of the liquids.

Idea Two:
Imagine that you fill three water balloons to the same size. One with pure water, one with soapy water, and the last one filled with vegetable oil. Do you think the balloons will appear the same when placed on a flat surface? If you think they would be different, why? Now actually doing this experiment would be a bit of a challenge, so we can just keep it as what’s called a thought experiment. But with a little ingenuity in the classroom or at home, it could be done. Just be careful not to pop the oil balloon!

Advance to Activity 1.2