Water is sticky!

Question:  How many drops of water (or soap water) can you fit on a coin?

Materials:  Coin, Small straw as dropper, Cup of water, soap

Prediction 1: How many drops of water do you think can fit on a coin?

Prediction 2: How many drops of soapy water can you fit on a coin?

Procedure: Put drops of water on your coin one at a time.  Record the number of drops that fit on the coin.  Your partner will help count and write the results.  When you are done let your partner try.  Repeat the experiment twice. Were your results the same in each experiment? Now try the same experiment with soapy water.

Was there a big difference between soapy water and tap water? Which is better at wetting surfaces- water or soapy water?

Explanation: Water molecules like to stick to each other. The soap breaks this sticky property of water and lets it wet and wash variety of surfaces.  This sticky property of water is called surface tension.

Try at home: What happens if you coat a coin with a drop of oil and then try the experiment?

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