Change the flow

Clean a pencil with soap and water, then hold it almost straight up and down over a sink or jar. Pour a thin stream of water from a glass or pitcher onto the side of the pencil. The water will run along the pencil and stream off the end of it.

Next, rub a few drops of vegetable oil onto the pencil. Try to make the water flow down the pencil as before. What happened?

What's Going On?

The water flowed neatly along the length of the pencil in the first experiment because water molecules stick to one another and to the side of the clean pencil. But the water does not flow along the length of the oiled pencil because water molecules do not stick to oil molecules. The water slides over the oil.

Source: highlightskids.com

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