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course PHY 202
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?
The amount of air in the tube decreases because there is less room for it in the bottle. I decreased the size of the bottle by squeezing it.
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Does the volume of air enclosed in the bottle increase or decrease?
The volume of air enclosed the bottle seems to decrease because I have squeezed the bottle and made its volume smaller.
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Does the pressure in the bottle increase or decrease?
The pressure in the bottle appears to stay the same, maybe increase a little. The air has left the bottle and in order to lower the pressure of the system.
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Does the temperature of the air in the bottle increase or decrease?
The temperature of the air in the bottle does not appear to increase.
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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?
The amount of air in the system stays the same because it has no way to escape the bottle. It may however, be compressed a little.
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Does the volume of air enclosed in the system increase or decrease?
The volume decreases a little since the air has been compressed.
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Does the pressure in the system increase or decrease?
The pressure in the system increases because I am doing work on the bottle and there is no way for the contents to escape.
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Does the temperature of the air in the system increase or decrease?
One would assume that the temperature would increase a little because the pressure on the bottle is increasing.
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This looks good. Let me know if you have any questions.
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course PHY 202
Siphon a plug of water into the tube, seal the end of the tube to create an air column between the plug and the sealed end, and screw the cap back on. Give the bottle a moderate squeeze. Note that the tube should have come with a cap on the end, but the cap might have been left off; if so you can seal the end with your thumb; if the end is cut at a sharp angle you can easily cut it off square.Does the air column get longer or shorter? By what percent do you estimate the length of the column changes?
I estimate that the column shrinks by about 1 cm. 1/7cm=14.3%
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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 probably by the same amount that the column length changed, so about 14.3%. The volume decreases because I am compressing the air. It cannot escape out the end of the tube because by thumb blocks it.
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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 number of air molecules in the tube stays the same, there is no way for them to escape.
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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 of the air remains the same because it cannot escape the tube. I estimate the mass changed by 0%.
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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 in the column will increase as I compress the bottle. Probably by about 14.8%.
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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?
The pressure in the bottle also increases, probably by the same amount the pressure everywhere else changes. 14.8%.
The pressure in the bottle also increases, probably by the same amount the pressure everywhere else changes. 14.8%.
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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?
Because the plug does not accelerate in either direction, the forces must be equal and opposite.
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Which do you think is greater, the pressure in the bottle or the pressure in the air column?
I think the pressure in the air column and the pressure in the bottle are the same.
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Measure the length of the air column.
What is the length of the air column?
7.2cm
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How far would the water plug have to move to make the air column 10% shorter?
.72cm
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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?
7
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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 -- .3cm
5 -- .5cm
8 - 1.2cm
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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:
+.2cm when bottle was heated (+2.8%)
-.1cm when bottle was cooled. (-1.4%)
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This looks good. Let me know if you have any questions.