Julie Franzak

5/24/2007

ELED 305-42

Science Area: Physics

Concept: Air Pressure

Three-Hole Bottle

Paradox #1

Grade: 5^th or 6^th

Materials:

2 liter plastic bottle with 3 small holes placed vertically on one side (about 6cm apart)

Holes can be made by heating a needle or stirring rod by melting the plastic or by drilling using an electric drill

Duct tape or electrician’s tape (about 18 cm long)

Scissors

Water

Cap

Basin (to catch water)

Towel

 

 

 

 

 

Safety Consideration:

Be careful of spilled water and slippery surfaces.

Discrepancy:

Many students will assume that once the first hole is uncovered, the water in the 2 liter bottle will begin to spill out. When the water doesn’t start to spill out when the first hole is uncovered, the students will then turn their attention to the second hole; when the second hole is uncovered, the water begins to spill out it, probably to the student’s predictions or hypotheses, but it does not spill out the first hole. Even when the third hole is uncovered, the water doesn’t spill out the first hole, it only comes out of the second and third holes in the bottle.

Procedures:

1. Show students the 3-hole bottle filled with water.

-“I’m going to uncover the first hole in the bottle.”

2. “Write down on your Report Paper what you think will happen when I do this. There should be not talking during this time.”

3. Ask students to tell their “predictions” to their classmates.

4. Prepare basin and ask a student participant to hold the bottle at the top and bottom without squeezing it.

5. Uncover the top hole.

6. Have students record what happens/the “results”.

7. Ask students for possible explanations for the “results”.

8. Ask students to write down their “hypothesis” or prediction of what will happen when the second hold is uncovered and then share some with the class.

9. Uncover the second hole.

10. Ask students if their “hypotheses” were right or wrong. (probably; possibly)

11. Have students record the “results”.

12. Have students write down their “predictions” of what will happen when the third hole is uncovered.

13. Ask students to share some of their predictions/hypotheses.

14. Uncover the third hold.

15. Have students record the “results”.

16. Have the students summarize the process that occurred in this activity.

17. Break the students into groups of 3-4 to retest the activity. Students should predict and record the results.

Questions:

1. What occurred when the first hole of the bottle was uncovered? (in groups of 2-3)

2. What will happen when the second hole is uncovered?

3. What will happen when the third hole is uncovered?

4. What forces are present on the water?

A1. Gravity on the water column.

A2. Air pressure on the plastic and water surface.

5. What is the air pressure on the water surface top before the cap is removed? After the cap is removed?

A1. Normal air pressure.

6. What is the air pressure on the water surface when the first hole is uncovered?

A1. Normal air pressure.

7. What happens at the first hole when the second hole is uncovered?

A1.

8. What does uncovering the second hole do to the air pressure on the surface top?

A1. Lower air pressure.

Explanation:

The gravity of the water when paired with the air pressure at the water surface causes the water to spill out of the second and third holes, but not the first hole. Although the air pressure changes noticeably between the second and third holes in the bottle as seen by the speed that the water spills out of each of them, it still does not spill out the first hole because the air pressure at the top of the water surface is still great enough that it hold the water in by gravity.

Source:

Hays, Leslie. Three-Hole Bottle. http://www.indiana.edu/~ensiweb/lessons/threehol.html. Obtained on May 22, 2007.