How do drinking straws work?
For grown-ups: the science
When you suck air from a straw, air pressure pushes the drink up into your mouth.
Suction does not pull liquid upward by itself. Lowering the pressure in the straw lets higher atmospheric pressure on the drink’s surface push the liquid up the straw. The height is limited by atmospheric pressure and the liquid’s weight.
What about...?
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Transcript
Your cup has a straw standing in it. How does the drink travel up to your mouth?
Put the straw in a drink and close your lips around the top. The straw makes a little path from the cup to your mouth.
When you suck, you take some air out of the straw. The air pushing on the drink in the cup helps move it up the straw.
The drink rises through the straw and into your mouth. It keeps moving while you keep sucking.
So a straw works because sucking lowers the air pressure inside it, and outside air pushes the drink up.