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course Phy 242
January 25 around 6pm.
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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Decrease, when squeezed, you’re pushing air out.
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Does the volume of air enclosed in the bottle increase or decrease?
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Decrease, same as above.
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Does the pressure in the bottle increase or decrease?
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Decrease, less air in the bottle.
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@&
The bottle remains open to the atmosphere, so the pressure at the end is the same as at the beginning. *@
Does the temperature of the air in the bottle increase or decrease?
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Decrease, the pressure decreases also.
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@& There might be a little temperature change because of your hand, but not much.*@
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, it stays the same because it is a sealed system.
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Does the volume of air enclosed in the system increase or decrease?
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Same as above.
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@& You do change the volume of the bottle when you squeeze it, thereby changing the volume of the air.*@
Does the pressure in the system increase or decrease?
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Increase, same amount of air and less space for it to be in.
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*#&!
@& 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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