Science with Sean: Siphon Straw

Published: Nov. 24, 2019 at 9:19 PM EST
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MYRTLE BEACH, SC (WMBF) - When you turn your faucet on, a stream of water pours out. But what if you could make your own faucet just using straws, bottles and the power of pressure and gravity. Let's move water upstream and show you how to make a simple siphon on this week's science experiment.

Ingredients are a bottle of water, we added food coloring so it's easier to tell. An empty bowl, 2 or more plastic straws, tape and scissors.

Step 1: Cut off one of the straws and then cut a diagonal part off of one end.

Step 2: Slide it in the small part of the other straw.

Step 3: Roll the tape on the connected straw.

Step 4: Put the straw with the taped half into the water. Put your finger on the top or suck on the straw to create suction.

Step 5: Pull out the straw and bend it over the bottle and watch it continue to pour. Take a guess how long it will pour for.

Why is this happening? A series of pressure differences makes water flow out of the higher cup, up the short arm, across the horizontal arm and down the long arm into the lower cup

This can be compared with scales beginning to tilt towards the heavier side.

As soon as water starts coming out of the long side of the siphon, pressure decreases, because water has flown out. This negative pressure causes water on the horizontal part of the siphon to be drawn (or, more accurately, pushed) into the long arm, which, in turn, pushes water from the short arm.

What powers this “pump”? Well, earth’s gravity helps siphons function, and without it, water would not have weight or exert any pressure and therefore not have any flow.

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