Traveling Water

How Does It Work

You probably know that water is H₂O and also know that each molecule of water is made up of two hydrogen atoms (H) and one oxygen atom (O). A drop of water has a gazillion molecules that are held together by electrical, molecular bonds. In this case, it’s called hydrogen bonding and it’s quite strong. These strong hydrogen bonds allow water molecules to stick together very well and move down the string into the bottom cup. When like molecules grab each other, it’s called cohesion.

You moistened the string to help the water molecules stick together and stick to the string. Water molecules can stick to other materials, too. This property of different molecules sticking to each other is called adhesion. In this case, water molecules stick to the string and other water molecules stick to them. It’s likely that some water dripped off of the string somewhere on its downhill trip. This is because adhesion is not as strong as cohesion.

Science Fair Connection

Pouring water using a string is pretty cool, but it isn’t a science fair project, yet. You can create a science fair project by identifying a variable, or something that changes, and deciding on something to measure in this experiment. Let’s take a look at some of the variable options that might work:

• Use a different liquid, like milk or soda. Which liquids have the best cohesion?
• Use different “strings” such a as a kite string or shoelace. Which materials allow the best adhesion?
• Does the temperature or dampness of the string make a difference?

That’s just a few ideas, but you aren’t limited to those! Try coming up with different ideas of variables and give them a try. Remember, you can only change one thing at a time. If you are measuring the distance the objects travel, make sure that the other factors are remaining the same!