#$&*
course phy242
Are we supposed to write out the textbook homework questions and submit those also?
Brief Bottle Experiment 1A: Basic concepts of N, P, V, TIt is assumed that you have read through the file Physics_II_Initial_Bottlecap-and-tube_Experiments.htm, which will familiarize you with the bottlecap and tube and some of their uses.
The bottlecap can be screwed onto a typical soft-drink bottle. It probably won't work on a bottle which isn't designed for the higher pressure of a carbonated drink, such as a water bottle or some tea bottles. A larger bottle is preferable, but any size will work adequately. A clear bottle is preferable to a colored bottle since you're going to sometimes want to see what's happening inside the bottle, and a darkly colored bottle won't allow this.
Screw the bottlecap onto a bottle and squeeze the bottle. It should be no surprise that if the tube isn't capped, this will force air out of the tube.
Comparing the state of the bottle before and after you squeeze:
Does the amount of air in the bottle increase or decrease?
****
Air leaves the end of the tube so it decreases
#$&*
Does the volume of air enclosed in the bottle increase or decrease?
Decrease, you change the physical geometry of the bottle when you squeeze it into the shape of a plate as opposed to its original cylindrical form
****
#$&*
Does the pressure in the bottle increase or decrease?
The pressure in the bottle remains the same because the hose is not capped. There is no pressure build up.
****
#$&*
Does the temperature of the air in the bottle increase or decrease?
The temperature remains the same because the mass (n) of air decreases with the decrease in volume. Pv=nrT
****
#$&*
Be sure you have explained all your answers.
Now cap the end of the tube and give the bottle a good squeeze, without straining yourself.
Comparing the state of the bottle before and after you squeeze:
Does the amount of air in the system increase or decrease?
****
The amount of air in the bottle (n) remains the same
#$&*
Does the volume of air enclosed in the system increase or decrease?
****
When you squeeze the bottle changine its physical geometry, volume decreases
#$&*
Does the pressure in the system increase or decrease?
****
Pressure in the bottle increases PV=nrT
#$&*
Does the temperature of the air in the system increase or decrease?
****
Temperature increases as air is compressed. Pressure and volume do not increase and decrease on a linear scale. Pressure increases exponentially greater than the decrease in volume
causing temperature to increase in order to balance the right side of the equation Pv=nRT
#$&*
Siphon a plug of water into the tube, seal the end of the tube to create an air column between the plug and the sealed end, and screw the cap back on. Give the bottle a moderate squeeze. Note that the tube should have come with a cap on the end, but the cap might have been left off; if so you can seal the end with your thumb; if the end is cut at a sharp angle you can easily cut it off square.
Does the air column get longer or shorter? By what percent do you estimate the length of the column changes?
****
The column of air between my thoumb and the water column gets shorter by a distance of one whole length of the column of water.
I can confirm this because there is more than one column of water in my tube. The smaller columns move one length and the larger columns move one length
#$&*
Does the volume of the air column increase or decrease? By what percent do you estimate the volume of the column changes?
The volume of air decreases. One column of water with six inches of air between it and my thumb becomes about three inches when i squeeze the bottle. So about 50 percent
****
#$&*
Does the number of molecules in the air column increase, decrease or remain the same? By what percent do you estimate the number of molecules changes?
The number of molecules in the air remains completely the same
****
#$&*
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?
Mass of air in the column remains the same
****
#$&*
Does the pressure in the air column increase, decrease or remain the same? By what percent do you conjecture the pressure in the column changes?
To compress a six inch cylinder of air to half the volumn. PV=nrT or nrT/V=P or C/V=P--> 2P=C/2V would require twice as much pressure.
****
#$&*
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 increases twice as much whenever the column of water moves one full length of itself
****
#$&*
When you hold the bottle in the squeezed position, with the water plug stationary, the pressure in the bottle results in a force on the plug which pushes it toward the capped end, while the pressure in the air column results in a force that pushes the plug away from that end. Which force do you think is the greater, or are they equal?
The forces are in equilibrium
****
#$&*
Which do you think is greater, the pressure in the bottle or the pressure in the air column?
The forces are in equilibrium as long as nothing breaks
****
#$&*
Measure the length of the air column.
What is the length of the air column?
6 inches
****
#$&*
How far would the water plug have to move to make the air column 10% shorter?
10 %
****
#$&*
Squeeze the bottle so the air column becomes 10% shorter. It's up to you to figure out how to tell when it's 10% shorter. If you can't squeeze hard enough to achieve the 10% difference, then figure out what percent you can manage and note the percent in your answer.
On a 1-10 scale, with 10 the hardest squeeze of which you are capable without risking injury, how hard did you have to squeeze the bottle and what percent change did you achieve in the length of the air column?
I hardly squeezed, I give it a 1
****
#$&*
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?
The column moves 20 percent at a squeeze of 2, 50 percent at a squeeze of 50 and 120 percent at a squeeze of 8
****
#$&*
@&
The air column is in the end of the tube with your thumb over it. With a harder squeeze it will get shorter.
It cannot get 120 percent shorter than its original length. This would result in a length less than zero.
*@
Now by heating and/or cooling the bottle, what extremes in air column length can you achieve? Careful not to melt the bottle. It won't handle boiling water, and you shouldn't mess with water hot enough to scald you or cold enough to injure you (e.g., don't use dry ice, which in any case is too cold for the bottle, and certainly don't use liquid nitrogen).
By heating the column in the microwave to sub boiling temperatures I achieved 30 percent greater compression
Report your results:
****
#$&*
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.
3% less air volume
****
#$&*
Estimate the percent change in the number of molecules in the air within the capped bottle.
0% change in number of air molecules
****
#$&*
Estimate the percent change in the volume of the water in the open bottle.
3%
****
#$&*
What do you think is the percent change in the air pressure in the capped bottle?
Pressure greatly increased although there was only a little bit of water that syphoned through. with a volume change of 3 percent I would suspect 6 percent higher pressure
****
#$&*
What is the difference in the two fluid levels?
9 cm
****
#$&*
What is the percent change in the number of air molecules in the capped bottle?
****
#$&*
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?
5%
****
#$&*
Estimate the percent change in the number of molecules in the air within the capped bottle.
No change in molecules
****
#$&*
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)?
10 % increase in pressure
****
#$&*
What percent of the uncapped bottle do you estimate is now occupied by air?
10%
****
#$&*
What is the difference in the two water levels?
31 cm
****
#$&*
Return the uncapped bottle to the tabletop. What happens?
Water syphed in the other direction to balance the pressure
What is now the difference in the two water levels?
9cm
****
#$&*
What do you think is the pressure in the uncapped bottle as a percent of its original pressure (before the bottle was capped)?
pressure stayed the same
****
#$&*
Add the extension to the tube, so that by squeezing you can force water from the bottle into the tube. Squeeze hard enough to raise the water to as high as possible into the tube. Evaluate how hard you had to squeeze, on the 1-10 scale you used in part 1b. Measure how far you were able to raise water in the tube above the level of the water in the bottle.
How high did you raise the water, and how hard did you have to squeeze (using the 1-10 scale)?
The tube was about five feet long and I squeezed with a force of about a 5 to send it through to the top
****
#$&*
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.
Squeeze height
1 14 inches
2 25 inches
3 34 inches
4 42 inches
5 48 inches
6 52 inches
7 55 inches
8 57 inches
9 59 inches
10 through the top
****
#$&*
"
@&
Good overall, but see my one inserted note and see if you can clarify your responses to that question and to those leading up to it.
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes. &#
*@