Siphon Bottle

Developer:

Charles Scaife
Department of Chemistry
Union College
Schenectady, NY 12308

Grade Levels:

4 through 12

Discipline:

Physical Science/Chemistry

Goals:

  1. To prepare a siphon bottle.
  2. To observe the behavior of a siphon bottle and try to understand the reasons for such behavior.
  3. To try to maximize the amount of water that can be dispensed from a siphon bottle.
  4. To work as a team to solve a problem.


Background:

I first heard about the Siphon Bottle from Cynthia Reedy in the Middle School at Hebron Academy in Hebron, ME. She showed me the apparatus and described the proceebron, ME. She showed me the apparatus and described the procedure for the experiment described for grades 4 through 8. Some aspects of the siphon bottle are presented in Friedl's Antigravity Fountain (1) and in Liem's Perpetual Fountain (2), but I have not seen the experiment described elsewhere.

The Siphon Bottle can be made from very simple pieces of equipment. Several modifications of the activity are possible depending on the grade level.

Teacher's Notes:

The Siphon Bottle can be used for any grades higher than about 4th grade. The bottle is already set up and its behavior is simply observed and discussed for grades 4-8. Play up the discrepant event aspect of this activity as much as possible. Lively discussion may still take 45 minutes for grades 9-12. Small groups of students try to prepare a siphon bottle to see which group dispenses the most water when the bottle is activated. A time limit of about 1/2 to 1 hour is allotted, but considerable discussion may follow.

Tygon® tubing can sometimes be purchased at a farm supply store as well as a scientific supply house or can be obtained from a local high school, college, or hospital. Rubber tubing may be used with considerable difficulty if you can't obtain Tygon® tubing. However, rubber tubing is too flexible to slip into the hole in the side of the bottle easily and into the correct configuration inside the bottle. Also rubber tubing sometimes crimps at the loop making it difficult for water to pass.

Materials:

FOR GRADES 4 THROUGH 8


  • 1 1-gallon opaque bleach bottle (with a hole drilled in the side about half way up the bottle and of an appropriate diameter similar to 7/16 inch so that the tubing can be slipped through the hole with some difficulty leaving a snug fit so that no leaks occur)
  • 1 3-foot length of 3/16" ID x 5/16" OD x 1/16" wall Tygon® tubing
  • 2 8-ounce paper or plastic cups
  • 1 3-lb coffee can

FOR GRADES 9 THROUGH 12


  • 1 1-gallon translucent windshield washer fluid bottle (with a hole drilled in the side about half way up the bottle and of an appropriate diameter similar to 7/16 inch so that the tubing can be slipped through the hole with some difficulty leaving a snug fit so that no leaks occur)
  • 2 3-foot lengths of 5/16" ID x 7/16" OD x 1/16" wall Tygon® tubing
  • 2 8-ounce paper or plastic cups
  • 1 3-lb coffee can
  • 1 pair Scissors (sturdy enough to cut the Tygon tubing)
  • 1 Waterproof tray in which to work


Explanation:

An opaque bottle is used for 4th through 8th graders so that studentat students specifically cannot see how the teacher has arranged the tubing inside the bottle. They are then forced to think about the options of how the tube is arranged and what are the consequences of such arrangements as the teacher leads a guided discussion. On the other hand, a translucent bottle is used for the 9th through 12th graders so that they can see how they are arranging the tubing and recognize more easily the consequences of their actions as they change the configuration of the tubing inside the bottle. These students are also provided with two lengths of tubing and scissors so that they can cut the tubing if they desire in order to accomodate a greater variety of arrangements.

Study carefully the explanation of how a siphon works under Question 6. In addition, the following should be noted.

In the 4th through 8th grade experiment, the key to the discrepant event is filling the bottle as close as possible to the top of the loop in the tubing but still keeping an air pocket in the tubing. As soon as sufficient water is added, the air is forced through the outlet of the tube, water flow begins, siphoning occurs, and the bottle empties unless the water flow is stopped either by pinching the tube or by raising the outlet so that it is above the inlet. Although a siphon can raise a liquid along the middle part of the tubing, the outlet can never be higher than the inlet. The net flow of liquid must always be downward. Draw the diagram under the Procedures on the board for reference by the teacher and students as the discussion proceeds. I have frequently made up bottles ahead of time with several configurations of tubing so that various modifications can be tested as students put forth ideas.

In the 9th through 12th grade experiment, all of the options in the Questions and many more are available to the students. The difference is that they can construct and test their ideas in a hands-on way rather than just thinking about them.

I received an interesting suggestion from a fifth grader that I have not yet been able to implement. The idea was to somehow place a float on the tubing where the upper loop should be as well as a weight on the inlet of the tubing in order to hold it below the water level of ther until the water level reaches the bottom of the bottle. Obviously both of these devices must be placed after the tubing is in the bottle, quite a chore working only through the mouth of the bottle. I do believe that the suggestion would work very well, assuming the float would not function once the water forced the loop into the narrowed mouth of the bottle, but is shows the practical difficulties that often arise.

Questions:

  1. Was the bottle empty when the experiment started? How do you know?

    The bottle could not have been empty when the experiment started. The water dispensed in addition to the water added from the cup had to come from the bottle and must have been in the bottle initially.


  2. If the tubing barely passed through the wall and into the bottle,
    1. How much water could be in the bottle before the experiment began? Why?
    2. How much water could be dispensed from the bottle when one cup of water was poured into the top of the bottle? Why?


    Water could have filled the bottle to the bottom of the tubing (or the bottom of the hole) before the experiment began. Any water in excess of that level would have passed out the tubing until the water was back down to that level. Any suction beyond this would have only pulled air.

    As much water could have been dispensed from the bottle as had been poured into the bottle in the first place, and no more. As soon as the water level dropped to the bottom of the tubing (or bottom of the hole), the flow of water would have ceased because any suction beyond this would have only pulled air.


  3. If the tubing passed into the bottle and then down to the bottom of the bottle,
    1. How much water could be in the bottle before the experiment began? Why?
    2. How much water could be dispensed from the bottle when one cup of water was poured into the top of the bottle? Why?


    Water could have filled the bottle to the bottom of the tubing (or the bottom of the hole) before the experiment began. If water had been above this level, it would have started to flow out the tubing. The resulting suction would have nearly emptied the bottle because the suction would not have pulled air until no water surrounded the inlet to the tubing at the bottom of the bottle.

    The total water dispensed could be the water required to fill the bottle to the hole plus one cup more because nearly all the water in the bottle would empty once the flow started and suction was initiated.


  4. If the tubing passed through into the bottle and then upward to near the mouth of the bottle,
    1. How much water could be in the bottle before the experiment began? Why?
    2. How much water could be dispensed from the bottle when one cup of water was poured into the top of the bottle? Why?


    The bottle could be filled to the inlet level of the tubing before the experiment began because no water would flow out of the tubing until the water level reached that point in the bottle.

    Only the water added from the cup could be dispensed from the bottle. Once this water had left the bottle any suction would only pull air. Note that if the inlet of the tubing sank deeper into the bottle as water flowed out, it might be possible to dispense some additional water.



  5. What other shapes of the tubing inside the bottle might dispense more water than any of the above alternatives?

    Any shape that involved a loop in the tubing at a level higher that the hole in the bottle would dispense more water than any of the above alternatives. The higher the loop in the bottle, the more water could be dispensed. Therefore, it is advantageous to have the loop just far enough below the mouth of the bottle to allow for added water to cover the loop and initiate suction.



  6. Explain how a siphon works.

    First, it is important to recognize what a siphon cannot do. Although a siphon can raise a liquid along the middle part of the tubing, the outlet can never be higher than the inlet. The net flow of liquid must always be downward. Note that this flow is weakly opposed to the differences in air pressure in that the higher inlet will have a marginally smaller air pressure pushing on the liquid than will the lower outlet with a marginally larger air pressure.

    Once liquid starts flowing through the tubing, however it is initiated, the movement of the liquid in the forward direction causes a pull or suction on the fluid behind it. That pull or suction creates the siphon.

    The fluid could be either air or water in the siphone bottle. It is easier to pull air than to pull water, but if there is no air inlet into the tubing and no air can get in, more water will be pulled, and the water flow will continue. Once the water level drops below the inlet of the tubing, air will be pulled into and through the tubing and the water flow will stop.



References:

  1. Alfred E. Friedl, Teaching Science to Children: An Integrated Approach, 2nd ed., McGraw-Hill, New York, NY, 1991, pp. 129, 131-3.
  2. Tik L. Liem, Invitations to Science Inquiry, 2nd ed., Science Inquiry Enterprises, Chino Hills, CA, 1987, (12.2) p. 23.


Procedure:

FOR 4th THROUGH 8th GRADERS

Construct the siphon bottle and fill it prior to use in the classroom.

Siphon Bottle Diagram


Drill a hole in the side of the opaque 1-gallon bleach bottle about half way up the bottle. The hole should be the same diameter as or slightly less than the diameter of the tubing to be used (approximately 7/16"). It is preferable to drill a smaller diameter hole first with an electric drill and then drill out the hole to the correct diameter with the drill turned on and then almost stopped before entry into the hole. This makes tearing of the hole less likely.

Slip about two feet of the Tygon tubing carefully through the hole in the side of the bottle. As shown in the sketch at the right, the tubing should first be angled upward to within about 2 inches of the mouth of the bottle and then curved around so that it swings back downward to the bottom of the bottle. You can catch the tubing with your finger as it comes near the mouth and guide it back downward, or you can make a hook from a coat hanger that will help to manipulate the tubing even inside the bottle. When the bends are proper, the tubing will hold itself in place. Occasional adjustment before use may be necessary.

It is important that you rehearse this experiment a few times. Prior to use in the classroom the bottle should be filled with water to just just ould be filled with cold water to just under the loop of tubing near the mouth of the bottle. No water should leave the tubing coming out the side of the bottle at this point because there is still air in the tubing from the loop onward.

Ask two children to help you with the experiment without telling anyone what is likely to happen. Place the bleach bottle on a stand or hold it just high enough so that a child can pour water into the bottle but can not see into the bottle through the mouth. The exit end of the tubing must be kept lower than the bottom of the bottle.

Give one child a full cup of water. This child is the pourer. Give the other child an empty cup. This child is the receiver. Also have the empty coffee can close by for reasons that will become obvious. Tell the first child to pour water into the mouth of the bottle until the second child receives a steady flow of water from the tube. If the bottle was filled according to the instructions above, only about half a cup of water should be necessary to start the flow

As the cup held by the second child nearly fills, ask the first child, for emphasis, how much water was poured into the bottle. Let the first child show the partially filled cup to the class. Simultaneously assist the receiving child by providing the coffee can to catch additional water. About this time it becomes obvious to obvious d is the pourer. Give the other child an empty cup. This child is the receiver. Also have the empty coffee can close by for reasons that will become obvious. Tell the first child to pour water into the mouth of the bottle until the second child receives a steady flow of water from the tube. If the bottle was filled according to the instructions above, only about half a cup of water should be necessary to start the flow.

To provide evidence for further discussion, let the receiving child fill the coffee can. Then stop the flow by pinching the tubing or placing the exit end of t the class that something strange is happening, that a discrepant event is taking place! Occasionally ask the first child again for emphasis how much water was poured into the bottle and how so much water is being obtained. Even though you have rehearsedhe tubing into the mouth of the bottle. This assures that more than enough water is collected to fill the bleach bottle above the hole through which the tubing passes.

Begin a discussion about how so much water was obtained from the bottle when less than a cup was initially poured into the bottle. The Questions provide good starters for discussion as well as a stepwise outline as to how the discussion might proceed.

FOR 9th THROUGH 12th GRADERS

Drill a hole in the side of the 1-gallon translucent windshield washer fluid bottles using the same procedure given in the second paragraph of the Procedure. Translucent bottles iiare used for these students so that they can see where the tubing is as they are proceeding with various modifications of the experimey can see where the tubing is as they are proceeding with various modifications of the experiment.

Divide the class into groups of four students. Provide the listed materials for each group. Without any prior instructions tell the groups that the challenge is to design and make a siphon bottle that will dispense the largest possible amount of water in addition to that poured into the mouth of the bottle. The bottle for each group will be demonstrated at the end of an appointed time (about 1/2 to 1 hour depending on the grade level), and a winner will be declared. If a group simply can't generate ideas to try, suggest they proceed stepwise through the Questions as a basis for their designs.

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