A sucker’s bet
Funny how we take every-day activities for granted. Take for instance – sucking through a straw. Have you ever stopped to think about how we are able to suck liquids through a straw. What exactly makes the liquid climb up the straw and into our mouths. Well, I know you’re just itching to know so here we go…
- Fill the jar with water.
- Poke a hole in the lid just big enough for the straw to fit through.
- Put the straw through the hole.
- Seal the hole with clay. Make sure it is sealed tight!
- Try to suck water through the straw.
What happens? When you drink from an open glass of water, air pressure allows the water to travel up the straw. By sucking on the straw you are reducing the air pressure inside your mouth. While sucking on the straw, the air pressure in your mouth is less than the air pressure outside of the straw (in the room, in the glass, etc.). The outside air pressure is pushing down on the water which forces the water up the straw. But when air pressure on the water is blocked (when you seal the jar lid), there is no air pressure to help push the water up your straw. The air can¹t get to the water to push on it, so it doesn’t go up the straw. Now matter how hard you suck, the water will not go up the straw.
Atmospheric pressure is one of the most common examples of pressure. It is produced by the weight of the air from the top of the atmosphere as it presses down upon the layers of air below it. At sea level, the average atmospheric pressure is 14.7 pounds per square inch (101.3 kilopascals). This decreases with altitude because of less air pressing from above.