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Q & A: Water, water everywhere!

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Most recent answer: 10/22/2007
Q:
Could I have some help on surface tension relating to the water molecule and intermolecular forces
- michella harris (age 16)
Cheltenham Girls, Australia
A:
Michella,
Water is a very special molecule and has some interesting properties. The one you're asking about is cohesion. Cohesion just means that the water molecules tend to stick together. For example, if you filled a bowl up with water, you could actually fill it until the water level was slightly higher than the bowl edge without it overflowing! This is what is described as having a high surface tension. Liquids with low surface tensions have week intermolecular forces and would overflow once the top of the liquid reached the height of the bowl.

Water molecules are cohesive because they are polar. This means that one side of a molecule has a slight postive charge, and the other side has a slight negative charge. The positive part on one molecule can attract the negative part of another molecule causing them to "stick" together.
That's all cohesion is!

~Ann

(published on 10/22/2007)

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