Expert: Sue Kayton Date: 2/18/2008 Subject: surface tension
Question I need help with my son's 5th grade science project .It relates to surface tension. His subject relates to physics and his problem is, How many pennies can be added to a glass of water that is already full?? He needs help understanding what surface tension and how it relates to his experiment.
Answer Water is made up of jillions of tiny little water molecules, just like a snowball is made up of lots of crystals of ice, or a dirt clod is made up ot lots of little specks of dirt. The ice crystals or dist specks stick together, just like water molecules stick together.
To see surface tension in action, turn a kitchen or bathroom faucet just a tiny bit on, so it drips very sloooowly. Watch the drop form, get bigger and bigger, and finally fall. Surface tension is what keeps the drop together, clinging to the faucet, until the drop gets so big that its weight pulls it down stronger than the surface tension holds it up.
You can also do this with a straw and some water.
You could also do the experiment of how much water can be added to a glass of water that is already full. If you add the drops slowly and carefully (use a straw with your finger over the top end to dispense drops), you can add water so it will bulge up over the top. The surface tension will keep the water together.
Why do water molecules stick together? One end is negatively charged and the other end is positively charged. Opposite charges attract,
