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course phy122
2/1 2
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 bottle decreases when a squeeze is applied while using the bottlecap that allows for air to pass through. Since there is no way to keep the air inside the bottle because it is uncapped, the air will escape, thus decreasing inside the bottle.
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Does the volume of air enclosed in the bottle increase or decrease?
The volume of air enclosed in the bottle also decreases. I am going to assume that there will be more air volume outside the bottle than inside when the bottle is squeezed and the air escapes.
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Does the pressure in the bottle increase or decrease?
The pressure in the bottle decreases. The air is decreasing, thus the pressure will decrease.
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If the pressure in the open bottle is greater than that of the atmosphere, air will be forced out of the opening.
If the pressure in the bottle is less than that of the atmosphere, air will be forced into the bottle.
For air to be forced out of the bottle the pressure inside must for a time increase.
The bottle is open at the beginning and at the end, so at the end of the process the pressure in the bottle will be the same as at the beginning (equal to that of the atmosphere both times).
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Does the temperature of the air in the bottle increase or decrease?
Well, I’m really not sure. I don’t know how we would measure that.
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This would in fact be very challenging to measure.
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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. I am not adding air to the bottle, it only increases pressure inside the bottle.
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Does the volume of air enclosed in the system increase or decrease?
The volume of air enclosed in the system will also stay the same. Again, I am not adding any air to the system. The original air is still inside the bottle, thus not decreasing or increasing.
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You are squeezing the bottle, which decreases its volume.
It is the decrease in the volume of the enclosed air that leads to the increase in its pressure.
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Does the pressure in the system increase or decrease?
The pressure in the system does increase. When I apply a squeeze to the bottle, the pressure inside will increase. When I release the squeeze the pressure will decrease.
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Does the temperature of the air in the system increase or decrease?
Again, I don’t know how we would measure this. I am going to assume that it does increase minimally due to the change in pressure.
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Good, but you have a couple of misconceptions so check my notes, which also provide you with additional information.
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