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course PHY 232
1/24 4:15 pm
Brief Bottle Experiment 1A: Basic concepts of N, P, V, TThe 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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Neither, since the bottle is capped tight no air can get in.
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Does the volume of air enclosed in the bottle increase or decrease?
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The volume decreases from being squeezed.
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Does the pressure in the bottle increase or decrease?
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Increases since the volume because the volume decreases since they are inversely related and of course the water moves into the tube from being forced out by the increased pressure.
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Does the temperature of the air in the bottle increase or decrease?
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The temperature does not increase since the friction of the squeeze or any other mechanical movements is nearly 0 and my hand is conducting that much heat into the bottle.
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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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Neither since both ends are 'airtight' no new air can enter.
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Does the volume of air enclosed in the system increase or decrease?
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Decreases again from being squeezed.
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Does the pressure in the system increase or decrease?
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Increases because of the decrease in volume and evidenced by the slight raising/lowering of the fluid level in the tube when squeezed/released.
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Does the temperature of the air in the system increase or decrease?
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Again, there's no real source of heat.
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@& Very good. It looks like you had water in the bottle during the first part. Had the bottle been empty, air would have been forced out of the tube and the pressure would have been the same after as before.
Followup:
Please submit a copy of the following questions and your answers, using the title "Followup to Brief Bottle Experiment 1a". The questions are brief and this should take you only a few minutes.
The main goal here is to associate what you have seen with the standard symbols for these quantities, and begin to think in terms of these symbols.
N stands for the number of air molecules in the bottle.
n stands for the number of moles of air in the bottle.
There are N_A = 6.02 * 10^23 particles in a mole, so N = n * N_A.
V stands for the volume of the gas.
T stands for its temperature.
P stands for the pressure within the bottle.
Answer the following:
If the sealed bottle is squeezed with the tube uncapped:
Which of the quantities P, V, N, n, T increase?
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Which of the quantities P, V, N, n, T decrease?
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Which of the quantities P, V, N, n, T remain unchanged?
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List the quantites that change, and give a rough estimate of the percent change in each when you squeezed. A positive percent means the quantity increased, a negative percent means the quantity decreaseed.
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If the sealed bottle is squeezed with the tube capped:
Which of the quantities P, V, N, n, T increase?
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Which of the quantities P, V, N, n, T decrease?
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Which of the quantities P, V, N, n, T remain unchanged?
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List the quantites that change, and give a rough estimate of the percent change in each when you squeezed. A positive percent means the quantity increased, a negative percent means the quantity decreaseed.
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If the temperature of the gas remains constant, the average speed of the molecules bouncing around inside the bottle also remains constant.
If this is the case, and the volume decreases, do the individual molecules strike the walls of the container harder, do they strike more frequently, or both? Explain
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