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course Phy 232
Brief Bottle Experiment 1A: Basic concepts of N, P, V, TIt is assumed that you have read through the file Physics_II_Initial_Bottlecap-and-tube_Experiments.htm, which will familiarize you with the bottlecap and tube and some of their uses.
The bottlecap can be screwed onto a typical soft-drink bottle. It probably won't work on a bottle which isn't designed for the higher pressure of a carbonated drink, such as a water bottle or some tea bottles. A larger bottle is preferable, but any size will work adequately. A clear bottle is preferable to a colored bottle since you're going to sometimes want to see what's happening inside the bottle, and a darkly colored bottle won't allow this.
Screw the bottlecap onto a bottle and squeeze the bottle. It should be no surprise that if the tube isn't capped, this will force air out of the tube.
Comparing the state of the bottle before and after you squeeze:
Does the amount of air in the bottle increase or decrease?
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Decreases
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Does the volume of air enclosed in the bottle increase or decrease?
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Decreases because as you squeeze, escapes through the opening.
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Does the pressure in the bottle increase or decrease?
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The pressure stays constant because the volume decreased compensating for the lessened air.
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Does the temperature of the air in the bottle increase or decrease?
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Stays constant because pressure is the same.
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Be sure you have explained all your answers.
Now cap the end of the tube and give the bottle a good squeeze, without straining yourself.
Comparing the state of the bottle before and after you squeeze:
Does the amount of air in the system increase or decrease?
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Air stays contained in the bottle so it is the same.
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Does the volume of air enclosed in the system increase or decrease?
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Volume decreased because you squeeze it.
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Does the pressure in the system increase or decrease?
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Pressure increases because volume decreased.
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Does the temperature of the air in the system increase or decrease?
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By theory the temperature increased but it is only by a small amount because you cannot squeeze it that hard.
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Does the air column get longer or shorter? By what percent do you estimate the length of the column changes?
The air column should be the same.
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Does the volume of the air column increase or decrease? By what percent do you estimate the volume of the column changes?
The volume decreases sue to the squeeze. Approx 15%.
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Does the number of molecules in the air column increase, decrease or remain the same? By what percent do you estimate the number of molecules changes?
The air molecules stays constant.
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Does the mass of the air in the air column increase or decrease? By what percent do you estimate the mass of the air in the column changes?
The mass would stay constant if the molecules is the same.
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Does the pressure in the air column increase, decrease or remain the same? By what percent do you conjecture the pressure in the column changes?
The pressure increases because volume decreased. 15%
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Does the pressure in the bottle increase, decrease or remain the same? By what percent do you conjecture the pressure in the bottle changes?
Refer above.
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When you hold the bottle in the squeezed position, with the water plug stationary, the pressure in the bottle results in a force on the plug which pushes it toward the capped end, while the pressure in the air column results in a force that pushes the plug away from that end. Which force do you think is the greater, or are they equal?
They are approx. equal because the plug does not move much.
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Which do you think is greater, the pressure in the bottle or the pressure in the air column?
The pressure in the bottle is probably greater because its volume changed the most.
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Measure the length of the air column.
What is the length of the air column?
9 cm.
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How far would the water plug have to move to make the air column 10% shorter?
It would have to move about halfway back toward the bottle.
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Squeeze the bottle so the air column becomes 10% shorter. It's up to you to figure out how to tell when it's 10% shorter. If you can't squeeze hard enough to achieve the 10% difference, then figure out what percent you can manage and note the percent in your answer.
On a 1-10 scale, with 10 the hardest squeeze of which you are capable without risking injury, how hard did you have to squeeze the bottle and what percent change did you achieve in the length of the air column?
I could not accurately control the air column.
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Now, using the same 1-10 scale, give the bottle squeezes of 2, 5 and 8. Estimate the percent changes in the length of the air column.
What were your percent changes in air column length?
2-3%
5-5%
8-8%
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Now by heating and/or cooling the bottle, what extremes in air column length can you achieve? Careful not to melt the bottle. It won't handle boiling water, and you shouldn't mess with water hot enough to scald you or cold enough to injure you (e.g., don't use dry ice, which in any case is too cold for the bottle, and certainly don't use liquid nitrogen).
Report your results:
Heating made the air column grow while cooling it made it shrink.
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Starting with the cap in place on an empty bottle, siphon water from an adjacent full bottle. Allow the siphon to run a few minutes until the water levels in the two bottles stabilize.
Estimate the percent change in the volume of the air in the capped bottle.
Volume was cut by about 20%.
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Estimate the percent change in the number of molecules in the air within the capped bottle.
The air molecules increased by about 20%-assuming the water and air molecules are identical.
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Estimate the percent change in the volume of the water in the open bottle.
20%
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What do you think is the percent change in the air pressure in the capped bottle?
The air pressure decreased because water ran out of the hose.
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What is the difference in the two fluid levels?
There is a 2 cm difference.
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What is the percent change in the number of air molecules in the capped bottle?
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Raise the open bottle as high as possible without disturbing the capped bottle. Allow time for the water levels in the two bottles to stabilize.
What percent of the volume of the capped bottle do you now estimate is occupied by water?
It is probably about 40%
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Estimate the percent change in the number of molecules in the air within the capped bottle.
It dropped about 20%
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By what percent do you estimate the pressure in the capped bottle exceeds the original pressure (i.e., the pressure when the bottle was first capped)?
It is probably about the same however it may be a little greater. Maybe 5% at the most.
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What percent of the uncapped bottle do you estimate is now occupied by air?
It is almost entirely air. 98%
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What is the difference in the two water levels?
20cm
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Return the uncapped bottle to the tabletop. What happens?
What is now the difference in the two water levels?
The water flows back into the uncapped bottle almost to a even level..
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What do you think is the pressure in the uncapped bottle as a percent of its original pressure (before the bottle was capped)?
It is again probably close to the same but it may be a little lower because the fluid flows into it.
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Add the extension to the tube, so that by squeezing you can force water from the bottle into the tube. Squeeze hard enough to raise the water to as high as possible into the tube. Evaluate how hard you had to squeeze, on the 1-10 scale you used in part 1b. Measure how far you were able to raise water in the tube above the level of the water in the bottle.
How high did you raise the water, and how hard did you have to squeeze (using the 1-10 scale)?
It raised a few cm and I squeezed about a 7.
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Give the bottle a squeeze corresponding to 1 on the 1-10 scale, and observe how high water rises. Then give it another squeeze, halfway between 1 and the squeeze you used to raise water to the top of the tube. Do this blind. Don't look at the tube, just feel the squeeze. Then look at the tube and see where the water is.
Report a table of water column height vs. squeeze.
The water is much lower than my 7 squeeze.
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&#Good work on this lab exercise. Let me know if you have questions. &#