# OS6 Solving Straw Power

Water goes downhill because of gravity. Water defies gravity going up a straw. How?

Question: How does a straw work?
Materials:
2 clear straws
Clear glass of liquid (can be colored)
Procedure:
Put a finger over the end of a straw
Put the other end in the glass of liquid against the side of the glass

It’s hard to see but only a little bulge of liquid is at the bottom of the straw while the top is covered with a finger.

Observe what happens
Take your finger off the end of the straw
Observe what happens
Put your finger over the end of the straw and lift it out of the glass

Keeping the end of the straw blocked with a finger lets the column of liquid get lifted out.

Observe what the liquid does
Take your finger off the end of the straw (Hold it over the glass!)
Observe what the liquid does
Take a drink through the straw

Sarah finds drinking with one straw is easy. She pulls all the air out of the straw and juice rushes up fill he space.

Observe how you do this, how your mouth works
Put the second straw in the glass of liquid
Take a drink through both straws at once
Observe how you do this, how your mouth works
Take one of the straws out of the glass so one ends in teh glass and one out of the glass
Take a drink through both straws at once
Observe how you do this, how your mouth works
Observations:
Describe what was in the straw when your finger is on the top
Describe what is in the straw after removing your finger

When the straw is not blocked, liquid fills it up to the same level as in the glass.

Describe what the liquid does when you lift the straw
Describe what the liquid does when you remove your finger
Describe how you use a straw to take a drink

Two straws let Sarah drink her juice faster.

Describe how you use both straws to take a drink
Describe taking a drink with one straw in the glass, one out of the glass
Conclusions:
Why doesn’t liquid go into the straw when the top is blocked?
What happens when you take your finger off the straw?

Holding the filled straw over the table and taking the finger off is a way to make a big mess. Air rushes in and pushes the water out.

Why doesn’t air keep you from taking a drink with a straw?
Why can’t you take a drink through two straws when one is outside the glass?

What I Found Out:

I found two large diameter straws to use. For the first parts of the project I used water with a little blue food coloring. One drop was too much and I kept diluting itt until the water was light blue.

First I held a finger on the top of the straw and pushed it into the water. No water went into it. A small bulge was visible at the bottom.

Air filled the tube. When my finger was on top and water on the bottom, the air couldn’t go in or out. It kept the water out as there wasn’t room for both. As soon as the air could get out, it did letting the water fill the tube.

As soon as I took my finger off the top, water rushed in so the level inside and outside of the straw was the same. I put my finger back on top and lifted it out of the water. The water inside lifted up too and didn’t fall out until I took my finger off the top.

This time the water was trapped inside and kept the air out. Once air could get inside, the water left.

My friend Sarah Brown helped me with the rest of the project as it is difficult to drink through a straw and take pictures of me doing it at the same time.

When Sarah used one straw, she pulled all the air out of it and juice rushed in to fill it up. Two straws worked the same way only doubling the amount of juice Sarah could drink.

Sarah is trying to get a drink of juice. Air rushes in the straw on the outside replacing all the air she pulls out of the other straw so the juice can’t get into the straw.

Everything changed when one straw was in the juice and one was outside the glass. Now Sarah tried to pull all the air out of the straw but more air kept coming back. No juice would get pulled up.