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course ormatting Guidelines and Conventions
12/15 12You should have a permanent notebook dedicated to the lab portion of this course. You should keep a record of the lab work you do, including free-hand sketches of apparatus and reasonably accurate but not meticulous hand-sketched graphs (you will likely use the computer to make meticulous graphs, but in the hand-sketching process you think about important aspects of the graph that don't necessarily become apparent if you use a machine to do the sketching).Some of your data will be taken by a computer or with the aid of a computer, and you will not be expected to write down the hundreds or thousands of data points involved in that process, but you should keep a small sample indicative of the results you obtain, and preliminary observations on trends and other aspects of your data which might be relevant to what you are observing.
You should also keep a record of where your data files are located, and you should maintain a secure backup of all your data files. If you lose your data, you might end up having to repeat your experiment.
You might at any point in the course be asked to reproduce information from your lab work. You lab notebook will be the key to being able to do so.
Indicate below, in your own words, the importance of maintaining a good lab notebook.
I should maintain a good lab notebook so that I can refer back to it in future assignments.
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It will be very important in your course that you report data in a way that can be both easily understood and electronically processed by your instructor and by your fellow students.
Report 4 two-digit numbers (e.g., 78 is a two-digit number; you can make up any four such numbers you like), one to each line, with a short note starting at the 5th line indicating how you chose your numbers (the note and the explanation should be brief and uncomplicated; it's not intended to be difficult. Anything you put down will be fine.)
your brief discussion/description/explanation:
23
25
27
29
These are all odd numbers
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Next report four 2-digit numbers in one line, separated by commas, and a short note starting at the 2d line briefly explaining how this format is different than the one in your preceding response.
your brief discussion/description/explanation:
23, 45, 67, 89
This format is different and is harder to read than having each number on its own line
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Suppose we have a meter stick oriented to that readings run in cm from left to right. Suppose we also have some object sitting at the 15 cm position. Another object at the 25 cm position will be 10 cm to the right of the first object, so the position of the second object relative to the first is +10 cm (remember that increasing numbers go to the right, so + indicates an object to the right of the reference position).
A third object sitting at the 5 cm mark will have a position relative to the first of -10 cm (as we move to the left readings on the meter stick decrease, so the - sign indicates a position to the left of the reference object).
An object with a position relative to the first object of -5 cm will be 5 cm to the left of the reference object, which will place it at the 10 cm mark of the ruler.
Call the position of the first object the reference position. Then an object at +25 cm relative to the reference position will be 25 cm to the right of the 15 cm mar, putting it at the 40 cm mark.
Jot down your answers to the following in your lab notebook. It is suggested that you accompany your answers with a sketch. If you don't yet have a dedicated lab notebook
• What would the position relative to the reference object of an object at the 20 cm mark?
• Where on the ruler would be an object at position -7 cm relative to the reference object?
• If an object is at the 2 cm mark on the ruler, what is its position relative to the reference position?
• What is the position on the ruler of an object located at +35 cm with respect to the reference position?
Place your answers in the first line of the indicated space below, with commas between your answers. Place only numbers and commas in this line.
On the second line specify the meaning of the numbers on the first line, and the units represented by those numbers (the units here are centimeters).
Then give a brief explanation of your understanding of the concept of relative position.
your brief discussion/description/explanation:
+5 cm, 8 cm, -13 cm, 50 cm
The number with a (+) or (-) in front represent the position relative to the reference point on the ruler. The other numbers are an actual position on the ruler that were described by a position relative to the reference point. Relative position indicates the location of an object in relation to another object.
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Suppose the y positions 5, 12, 21, 37, in cm, occur at respective clock times 2,4,6,8 seconds. A comma-delimited table of y vs. t would then consist of 4 lines with the t value first and the y value second.
Important convention: When we list one quantity vs. the second quantity, it's the second quantity, the one after the 'vs.', that goes in the first column. Remember this.
So the table corresponding to the above information would be
2, 5
4, 12
6, 21
8, 37
Suppose now that temperatures of 80, 60, 50 and 45 deg occur at clock times 3, 10, 24 and 41 minutes.
Report this temperature vs. clock time data in the indicated space below, in comma-delimited format as explained above. Use numbers only--no units. The units will be explained in your additional lines.
Then add a sentence or two starting in the fifth line, which specifies what these number mean: which number is first, which is second, and why; what quantity is belng listed vs. what; and in what units each quantity is being reported.
your brief discussion/description/explanation:
3, 80
10, 60
24, 50
41, 45
The way I see it, these numbers are listed like a set of coordinates (x. y) and the x coordinate always precedes the y. The x coordinates indicate clock times and are reported in minutes. The y coordinates indicate temperature are reported in degrees.
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Suppose that in a flow experiment depths of 30, 20, 14 and 9 cm occur at clock times of 2, 12, 24 and 36 seconds. List the clock times only in the first line, separated by commas. List the depths only in the the second line, also in comma-delimited format. Starting in the third line, briefly explain what you did.
your brief discussion/description/explanation:
2, 12, 24, 36
30, 20, 14, 9
I first listed the clock times in the first line, and listed the depths in the second line. The paired coordinates match up vertically.
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Now go into Notepad or another text editor, list the ordered pairs indicating the data just given above, but in tab-delimited format.
You have to go into another program to enter tabs because if you try to enter a tab on the form, it will 'jump' you to the next 'answer box'.
Enter your data so that on the first line you have your first clock time, then a single tab (hit the 'tab' key on your keyboard), followed by the first depth.
Then add a line for each subsequent data point, so that you have reported your information on four lines delimited by tabs.
On the fifth line, specify the units of the data you have given. Starting in the next line give a very brief explanation of what you just did.
Then highlight, copy and paste this data into the form.
your brief discussion/description/explanation:
2 30
12 20
24 14
36 9
s cm
I just paired these data points together on the same line separated by a tab.
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Suppose that the third column of the Timer program shows the numbers 3.7, 4.3, 5.2, 3.9, 4.3. Recall that the third line consists of the time intervals between clicks.
The clock time of the first click would be in the middle column. If necessary, briefly review the TIMER program, or the data you have obtained from that program.
We will define the 'first click' as the one that occurred at the beginning of the 3.7-second interval.
What would be the clock time relative to the first click of each of the four given numbers from the third line?
List these clock times in the first line in comma-delimited format. In the second line indicate the units of the numbers you have placed in the first line, and explain how you obtained the clock times.
your brief discussion/description/explanation:
8, 13.2, 17.1, 21.4
The units are in seconds. I obtained these times by adding the second time interval to the first, then the first two added to the third, etc. Essentially, I added the time intervals to get the clock time relative to each click.
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Suppose that in a room at temperature 23 C, an experiment reports 50 C, 40 C, 35 C and 31 C. Report these temperatures in Celsius degrees in the first line, using comma-delimited format. In the second line report in the same format the temperatures relative to room temperature. In the third line specify what the units are, that the second-line temperatures are relative to room temperature, and also report the room temperature.
your brief discussion/description/explanation:
50 C, 40 C,35 C, 31 C
+27, +17, +12, +8
The units are in degrees celcius, and the numbers in the second line represent the relative value of the numbers in the first line in relation to room temperature, at 23 C.
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Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
Approximately how long did it take you to complete this experiment?
45 mins
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You may also include optional comments and/or questions.
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self-critique rating"
Self-critique (if necessary):
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Self-critique rating:
________________________________________
`gr91
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course ottle Thermometer
kp2395@email.vccs.edu
12/15 7
· Refer back to the experiment 'Measuring Atmospheric Pressure' for a detailed description of how the pressure-indicating tube is constructed for the 'stopper' version of the experiment.
For the bottle-cap version, the pressure-indicating tube is the second-longest tube. The end inside the bottle should be open to the gas inside the bottle (a few cm of tube inside the bottle is sufficient) and the other end should be capped.
The figure below shows the basic shape of the tube; the left end extends down into the bottle and the capped end will be somewhere off to the right. The essential property of the tube is that when the pressure in the bottle increases, more force is exerted on the left-hand side of the 'plug' of liquid, which moves to the right until the compression of air in the 'plugged' end balances it. As long as the liquid 'plug' cannot 'leak' its liquid to the left or to the right, and as long as the air column in the plugged end is of significant length so it can be measured accurately, the tube is set up correctly.
If you pressurize the gas inside the tube, water will rise accordingly in the vertical tube. If the temperature changes but the system is not otherwise tampered with, the pressure and hence the level of water in the tube will change accordingly.
When the tube is sealed, pressure is atmospheric and the system is unable to sustain a water column in the vertical tube. So the pressure must be increased. Various means exist for increasing the pressure in the system.
· You could squeeze the bottle and maintain enough pressure to support, for example, a 50 cm column. However the strength of your squeeze would vary over time and the height of the water column would end up varying in response to many factors not directly related to small temperature changes.
· You could compress the bottle using mechanical means, such as a clamp. This could work well for a flexible bottle such as the one you are using, but would not generalize to a typical rigid container.
· You could use a source of compressed air to pressurize the bottle. For the purposes of this experiment, a low pressure, on the order of a few thousand Pascals (a few hudredths of an atmosphere) would suffice.
The means we will choose is the low-pressure source, which is readily available to every living land animal. We all need to regularly, several times a minute, increase and decrease the pressure in our lungs in order to breathe. We're going to take advantage of this capacity and simply blow a little air into the bottle.
· Caution: The pressure you will need to exert and the amount of air you will need to blow into the system will both be less than that required to blow up a typical toy balloon. However, if you have a physical condition that makes it inadvisable for you to do this, let the instructor know. There is an alternative way to pressurize the system.
You recall that it takes a pretty good squeeze to raise air 50 cm in the bottle. You will be surprised at how much easier it is to use your diaphragm to accomplish the same thing. If you open the 'pressure valve', which in this case consists of removing the terminating cap from the third tube, you can then use the vertical tube as a 'drinking straw' to draw water up into it. Most people can easily manage a 50 cm; however don't take this as a challenge. This isn't a test of how far you can raise the water.
Instructions follow:
· Before you put your mouth on the tube, make sure it's clean and make sure there's nothing in the bottle you wouldn't want to drink. The bottle and the end of the tube can be cleaned, and you can run a cleaner through the tube (rubbing alcohol works well to sterilize the tube). If you're careful you aren't likely to ingest anything, but of course you want the end of the tube to be clean.
· Once the system is clean, just do this. Pull water up into the tube. While maintaining the water at a certain height, replace the cap on the pressure-valve tube and think for a minute about what's going to happen when you remove the tube from your mouth. Also think about what, if anything, is going to happen to the length of the air column at the end of the pressure-indicating tube. Then go ahead and remove the tube from your mouth and watch what happens.
Describe below what happens and what you expected to happen. Also indicate why you think this happens.
****I expected the water to go back down in the bottle, which indeed happened. This is because when I take my mouth off the tube, air moved back in the bottle to equalize the pressure with the atmosphere.
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Now think about what will happen if you remove the cap from the pressure-valve tube. Will air escape from the system? Why would you or would you not expect it to do so?
Go ahead and remove the cap, and report your expectations and your observations below.
****I do not expect anything to happen because the pressure already equalizes when I removed my mouth from the tube. I was correct, nothing happened when I removed the cap.
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Now replace the cap on the pressure-valve tube and, while keeping an eye on the air column in the pressure-indicating tube, blow just a little air through the vertical tube, making some bubbles in the water inside the tube. Blow enough that the air column in the pressure-indicating tube moves a little, but not more than half a centimeter or so. Then remove the tube from your mouth, keeping an eye on the pressure-indicating tube and also on the vertical tube.
· What happens?
****When I blew into the tube making some bubbles, the water in the tube moved up. When I removed my mouth, the water did not move down.
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· Why did the length of the air column in the pressure-indicating tube change length when you blew air into the system? Did the air column move back to its original position when you removed the tube from your mouth? Did it move at all when you did so?
****The length of the air column changed because I added pressure while blowing into the tube. The air column did not move at all when I removed my mouth.
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· What happened in the vertical tube?
****The water level increased in the vertical tube.
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· Why did all these things happen? Which would would you have anticipated, and which would you not have anticipated?
****The water increased in the tube to try to maintain atmospheric pressure as more air was added, and I expected this to happen. I didn’t expect that the water level would stay the same after I blew bubbles and then removed my mouth from the tube.
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· What happened to the quantities P, V, n and T during various phases of this process?
****P increased, V remained constant, number of moles increased, and T probably changed in response to the changes in P and n.
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Place the thermometer that came with your kit near the bottle, with the bulb not touching any surface so that it is sure to measure the air temperature in the vicinity of the bottle and leave it alone until you need to read it.
Now you will blow enough air into the bottle to raise water in the vertical tube to a position a little ways above the top of the bottle.
· Use the pressure-valve tube to equalize the pressure once more with atmospheric (i.e., take the cap off). Measure the length of the air column in the pressure-indicating tube, and as you did before place a measuring device in the vicinity of the meniscus in this tube.Replace the cap on the pressure-valve tube and again blow a little bit of air into the bottle through the vertical tube. Remove the tube from your mouth and see how far the water column rises. Blow in a little more air and remove the tube from your mouth. Repeat until water has reached a level about 10 cm above the top of the bottle.
· Place the bottle in a pan, a bowl or a basin to catch the water you will soon pour over it.
· Secure the vertical tube in a vertical or nearly-vertical position.
The water column is now supported by excess pressure in the bottle. This excess pressure is between a few hundredths and a tenth of an atmosphere.
The pressure in the bottle is probably in the range from 103 kPa to 110 kPa, depending on your altitude above sea level and on how high you chose to make the water column. You are going to make a few estimates, using 100 kPa as the approximate round-number pressure in the bottle, and 300 K as the approximate round-number air temperature. Using these ball-park figures:
· If gas pressure in the bottle changed by 1%, by how many N/m^2 would it change?
****100kPa= 100,000N/m^2
(100,000 N/m^2)*(0.01) = 1000 N/m^2
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· What would be the corresponding change in the height of the supported air column?
****h= P/rho*g = (1000N/m^2)/[(1000kg/m^3)*(9.8m/s^2)] = 0.1m =10cm
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· By what percent would air temperature have to change to result in this change in pressure, assuming that the container volume remains constant?
****T would increase by 1%. #$&*
Continuing the above assumptions:
· How many degrees of temperature change would correspond to a 1% change in temperature?
****300K*0.01 = 3K. 300K+3K = 303K
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· How much pressure change would correspond to a 1 degree change in temperature?
****(1000N/m^2)/3= 333N/m^2
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· By how much would the vertical position of the water column change with a 1 degree change in temperature?
****h= P/(rho*g)= (1000N/m^2)/[1000kg/m^3 * 9.8m/s^2] = 0.01m = 10cm
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· How much temperature change would correspond to a 1 cm difference in the height of the column?
****P= rho*g*h = (1000kg/m^3)*(9.8m/s^2)*(0.01m) = 98N/m^2 = 98% increase
300K*0.98 = 294K change in temperature.
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· How much temperature change would correspond to a 1 mm difference in the height of the column?
****P= (1000kg/m^3)*(9.8m/s^2)*(0.001m)= 9.8N/m^2
300K*0.098= 29.4K temperature change
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A change in temperature of 1 Kelvin or Celsius degree in the gas inside the container should correspond to a little more than a 3 cm change in the height of the water column. A change of 1 Fahrenheit degree should correspond to a little less than a 2 cm change in the height of the water column. Your results should be consistent with these figures; if not, keep the correct figures in mind as you make your observations.
The temperature in your room is not likely to be completely steady. You will first see whether this system reveals any temperature fluctuations:
· Make a mark, or fasten a small piece of clear tape, at the position of the water column.
· Observe, at 30-second intervals, the temperature on your alcohol thermometer and the height of the water column relative to the mark or tape (above the tape is positive, below the tape is negative).
· Try to estimate the temperatures on the alcohol thermometer to the nearest .1 degree, though you won't be completely accurate at this level of precision.
· Make these observations for 10 minutes.
Report in units of Celsius vs. cm your 20 water column position vs. temperature observations, in the form of a comma-delimited table below.
****
20.0 C, 32.5 cm
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.1, 32.5
20.1, 32.5
20.1, 32.5
20.1, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.1, 32.5
20.1, 32.5
20.0, 32.5
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Describe the trend of temperature fluctuations. Also include an estimate (or if you prefer two estimates) based on both the alcohol thermometer and the 'bottle thermometer' the maximum deviation in temperature over the 10-minute period. Explain the basis for your estimate(s):
****The temperature fluctuations were very slight and appeared to be random. The deviation in the thermometer was 0.1 C, and their appeared to be no deviation in the ‘bottle thermometer’
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Now you will change the temperature of the gas in the system by a few degrees and observe the response of the vertical water column:
· Read the alcohol thermometer once more and note the reading.
· Pour a single cup of warm tap water over the sides of the bottle and note the water-column altitude relative to your tape, noting altitudes at 15-second intervals.
· Continue until you are reasonably sure that the temperature of the system has returned to room temperature and any fluctuations in the column height are again just the result of fluctuations in room temperature. However don't take data on this part for more than 10 minutes.
Report your results below:
****
45.2
42.9
40.6
38.0
36.8
35.8
35.1
34.6
34.0
33.7
33.3
32.9
32.7
32.5
32.5
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If your hands are cold, warm them for a minute in warm water. Then hold the palms of your hands very close to the walls of the container, being careful not to touch the walls. Keep your hands there for about a minute, and keep an eye on the air column.
Did your hands warm the air in the bottle measurably? If so, by how much? Give the basis for your answer:
****No, my hands did not measurably have an impact on the water in the column.
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Now reorient the vertical tube so that after rising out of the bottle the tube becomes horizontal. It's OK if some of the water in the tube leaks out during this process. What you want to achieve is an open horizontal tube,, about 30 cm above the level of water in the container, with the last few centimeters of the liquid in the horizontal portion of the tube and at least a foot of air between the meniscus and the end of the tube.
The system might look something like the picture below, but the tube running across the table would be more perfectly horizontal.
Place a piece of tape at the position of the vertical-tube meniscus (actually now the horizontal-tube meniscus). As you did earlier, observe the alcohol thermometer and the position of the meniscus at 30-second intervals, but this time for only 5 minutes. Report your results below in the same table format and using the same units you used previously:
****
20.0 C, 8.0 cm
20.0, 8.0
20.0, 8.0
20.0, 7.9
20.0, 7.9
19.9, 7.9
19.9, 7.9
19.9, 7.8
19.9, 7.8
19.9, 7.7
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Repeat the experiment with your warm hands near the bottle. Report below what you observe:
****Upon placing my warm hands near the bottle, the water quickly filled up the tube.
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When in the first bottle experiment you squeezed water into a horizontal section of the tube, how much additional pressure was required to move water along the horizontal section?
· By how much do you think the pressure in the bottle changed as the water moved along the horizontal tube?
****Very little force was required to move the water along the horizontal tube.
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· If the water moved 10 cm along the horizontal tube, whose inner diameter is about 3 millimeters, by how much would the volume of air inside the system change?
****V= pi*r^2*h= (3.1415)(0.0015m)^2*(0.1m) = 7.1*10^-7m^3= 0.71cm^3
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· By what percent would the volume of the air inside the container therefore change?
****>1%
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· Assuming constant pressure, how much change in temperature would be required to achieve this change in volume?
****>1%
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· If the air temperature inside the bottle was 600 K rather than about 300 K, how would your answer to the preceding question change?
****In this case, the required temperature change in the preceding question would double.
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There were also changes in volume when the water was rising and falling in the vertical tube. Why didn't we worry about the volume change of the air in that case? Would that have made a significant difference in our estimates of temperature change?
****We did not worry about the change in volume because it did not have a significant effect on the change in temperature. The water in the column was moving mainly because of the increased pressure from the increase in temperature.
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If the tube was not completely horizontal, would that affect our estimate of the temperature difference?
For example consider the tube in the picture below.
Suppose that in the process of moving 10 cm along the tube, the meniscus moves 6 cm in the vertical direction.
· By how much would the pressure of the gas have to change to increase the altitude of the water by 6 cm?
****P= rho*g*h = (1000kg/m^3)(9.8m/s^2)(0.06m) = 588N/m^2
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· Assuming a temperature in the neighborhood of 300 K, how much temperature change would be required, at constant volume, to achieve this pressure increase?
****(588N/m^2)/(100,000N/m^2)= 0.00588= 0.588%
300K*0.00588=1.76 degrees
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· The volume of the gas would change by the additional volume occupied by the water in the tube, in this case about .7 cm^3. Assuming that there are 3 liters of gas in the container, how much temperature change would be necessary to increase the gas volume by .7 cm^3?
****3L= 3000cm^3
0.7cm^3/3000cm^3= 2.3*10^-4= 0.023% change
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Continue to assume a temperature near 300 K and a volume near 3 liters:
· If the tube was in the completely vertical position, by how much would the position of the meniscus change as a result of a 1 degree temperature increase?
****1 K/300K= 0.33% change
3000cm^3*0.0033= 10cm^3
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· What would be the change if the tube at the position of the meniscus was perfectly horizontal? You may use the fact that the inside volume of a 10 cm length tube is .7 cm^3.
****
10cm/0.7cm^3= x cm/10cm^3. X= 143 cm change in length
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· A what slope do you think the change in the position of the meniscus would be half as much as your last result?
****I would assume that at a slope of 45 degrees, the change in meniscus position would be half as much as the last result.
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Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
· Approximately how long did it take you to complete this experiment?
4 hours
"
Self-critique (if necessary):
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Self-critique rating:
________________________________________
`gr91
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course ormatting Guidelines and Conventions
12/15 12You should have a permanent notebook dedicated to the lab portion of this course. You should keep a record of the lab work you do, including free-hand sketches of apparatus and reasonably accurate but not meticulous hand-sketched graphs (you will likely use the computer to make meticulous graphs, but in the hand-sketching process you think about important aspects of the graph that don't necessarily become apparent if you use a machine to do the sketching).Some of your data will be taken by a computer or with the aid of a computer, and you will not be expected to write down the hundreds or thousands of data points involved in that process, but you should keep a small sample indicative of the results you obtain, and preliminary observations on trends and other aspects of your data which might be relevant to what you are observing.
You should also keep a record of where your data files are located, and you should maintain a secure backup of all your data files. If you lose your data, you might end up having to repeat your experiment.
You might at any point in the course be asked to reproduce information from your lab work. You lab notebook will be the key to being able to do so.
Indicate below, in your own words, the importance of maintaining a good lab notebook.
I should maintain a good lab notebook so that I can refer back to it in future assignments.
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It will be very important in your course that you report data in a way that can be both easily understood and electronically processed by your instructor and by your fellow students.
Report 4 two-digit numbers (e.g., 78 is a two-digit number; you can make up any four such numbers you like), one to each line, with a short note starting at the 5th line indicating how you chose your numbers (the note and the explanation should be brief and uncomplicated; it's not intended to be difficult. Anything you put down will be fine.)
your brief discussion/description/explanation:
23
25
27
29
These are all odd numbers
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Next report four 2-digit numbers in one line, separated by commas, and a short note starting at the 2d line briefly explaining how this format is different than the one in your preceding response.
your brief discussion/description/explanation:
23, 45, 67, 89
This format is different and is harder to read than having each number on its own line
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Suppose we have a meter stick oriented to that readings run in cm from left to right. Suppose we also have some object sitting at the 15 cm position. Another object at the 25 cm position will be 10 cm to the right of the first object, so the position of the second object relative to the first is +10 cm (remember that increasing numbers go to the right, so + indicates an object to the right of the reference position).
A third object sitting at the 5 cm mark will have a position relative to the first of -10 cm (as we move to the left readings on the meter stick decrease, so the - sign indicates a position to the left of the reference object).
An object with a position relative to the first object of -5 cm will be 5 cm to the left of the reference object, which will place it at the 10 cm mark of the ruler.
Call the position of the first object the reference position. Then an object at +25 cm relative to the reference position will be 25 cm to the right of the 15 cm mar, putting it at the 40 cm mark.
Jot down your answers to the following in your lab notebook. It is suggested that you accompany your answers with a sketch. If you don't yet have a dedicated lab notebook
• What would the position relative to the reference object of an object at the 20 cm mark?
• Where on the ruler would be an object at position -7 cm relative to the reference object?
• If an object is at the 2 cm mark on the ruler, what is its position relative to the reference position?
• What is the position on the ruler of an object located at +35 cm with respect to the reference position?
Place your answers in the first line of the indicated space below, with commas between your answers. Place only numbers and commas in this line.
On the second line specify the meaning of the numbers on the first line, and the units represented by those numbers (the units here are centimeters).
Then give a brief explanation of your understanding of the concept of relative position.
your brief discussion/description/explanation:
+5 cm, 8 cm, -13 cm, 50 cm
The number with a (+) or (-) in front represent the position relative to the reference point on the ruler. The other numbers are an actual position on the ruler that were described by a position relative to the reference point. Relative position indicates the location of an object in relation to another object.
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Suppose the y positions 5, 12, 21, 37, in cm, occur at respective clock times 2,4,6,8 seconds. A comma-delimited table of y vs. t would then consist of 4 lines with the t value first and the y value second.
Important convention: When we list one quantity vs. the second quantity, it's the second quantity, the one after the 'vs.', that goes in the first column. Remember this.
So the table corresponding to the above information would be
2, 5
4, 12
6, 21
8, 37
Suppose now that temperatures of 80, 60, 50 and 45 deg occur at clock times 3, 10, 24 and 41 minutes.
Report this temperature vs. clock time data in the indicated space below, in comma-delimited format as explained above. Use numbers only--no units. The units will be explained in your additional lines.
Then add a sentence or two starting in the fifth line, which specifies what these number mean: which number is first, which is second, and why; what quantity is belng listed vs. what; and in what units each quantity is being reported.
your brief discussion/description/explanation:
3, 80
10, 60
24, 50
41, 45
The way I see it, these numbers are listed like a set of coordinates (x. y) and the x coordinate always precedes the y. The x coordinates indicate clock times and are reported in minutes. The y coordinates indicate temperature are reported in degrees.
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Suppose that in a flow experiment depths of 30, 20, 14 and 9 cm occur at clock times of 2, 12, 24 and 36 seconds. List the clock times only in the first line, separated by commas. List the depths only in the the second line, also in comma-delimited format. Starting in the third line, briefly explain what you did.
your brief discussion/description/explanation:
2, 12, 24, 36
30, 20, 14, 9
I first listed the clock times in the first line, and listed the depths in the second line. The paired coordinates match up vertically.
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Now go into Notepad or another text editor, list the ordered pairs indicating the data just given above, but in tab-delimited format.
You have to go into another program to enter tabs because if you try to enter a tab on the form, it will 'jump' you to the next 'answer box'.
Enter your data so that on the first line you have your first clock time, then a single tab (hit the 'tab' key on your keyboard), followed by the first depth.
Then add a line for each subsequent data point, so that you have reported your information on four lines delimited by tabs.
On the fifth line, specify the units of the data you have given. Starting in the next line give a very brief explanation of what you just did.
Then highlight, copy and paste this data into the form.
your brief discussion/description/explanation:
2 30
12 20
24 14
36 9
s cm
I just paired these data points together on the same line separated by a tab.
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Suppose that the third column of the Timer program shows the numbers 3.7, 4.3, 5.2, 3.9, 4.3. Recall that the third line consists of the time intervals between clicks.
The clock time of the first click would be in the middle column. If necessary, briefly review the TIMER program, or the data you have obtained from that program.
We will define the 'first click' as the one that occurred at the beginning of the 3.7-second interval.
What would be the clock time relative to the first click of each of the four given numbers from the third line?
List these clock times in the first line in comma-delimited format. In the second line indicate the units of the numbers you have placed in the first line, and explain how you obtained the clock times.
your brief discussion/description/explanation:
8, 13.2, 17.1, 21.4
The units are in seconds. I obtained these times by adding the second time interval to the first, then the first two added to the third, etc. Essentially, I added the time intervals to get the clock time relative to each click.
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Suppose that in a room at temperature 23 C, an experiment reports 50 C, 40 C, 35 C and 31 C. Report these temperatures in Celsius degrees in the first line, using comma-delimited format. In the second line report in the same format the temperatures relative to room temperature. In the third line specify what the units are, that the second-line temperatures are relative to room temperature, and also report the room temperature.
your brief discussion/description/explanation:
50 C, 40 C,35 C, 31 C
+27, +17, +12, +8
The units are in degrees celcius, and the numbers in the second line represent the relative value of the numbers in the first line in relation to room temperature, at 23 C.
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Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
Approximately how long did it take you to complete this experiment?
45 mins
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You may also include optional comments and/or questions.
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&#Very good responses. Let me know if you have questions. &#
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course ottle Thermometer
kp2395@email.vccs.edu
12/15 7
· Refer back to the experiment 'Measuring Atmospheric Pressure' for a detailed description of how the pressure-indicating tube is constructed for the 'stopper' version of the experiment.
For the bottle-cap version, the pressure-indicating tube is the second-longest tube. The end inside the bottle should be open to the gas inside the bottle (a few cm of tube inside the bottle is sufficient) and the other end should be capped.
The figure below shows the basic shape of the tube; the left end extends down into the bottle and the capped end will be somewhere off to the right. The essential property of the tube is that when the pressure in the bottle increases, more force is exerted on the left-hand side of the 'plug' of liquid, which moves to the right until the compression of air in the 'plugged' end balances it. As long as the liquid 'plug' cannot 'leak' its liquid to the left or to the right, and as long as the air column in the plugged end is of significant length so it can be measured accurately, the tube is set up correctly.
If you pressurize the gas inside the tube, water will rise accordingly in the vertical tube. If the temperature changes but the system is not otherwise tampered with, the pressure and hence the level of water in the tube will change accordingly.
When the tube is sealed, pressure is atmospheric and the system is unable to sustain a water column in the vertical tube. So the pressure must be increased. Various means exist for increasing the pressure in the system.
· You could squeeze the bottle and maintain enough pressure to support, for example, a 50 cm column. However the strength of your squeeze would vary over time and the height of the water column would end up varying in response to many factors not directly related to small temperature changes.
· You could compress the bottle using mechanical means, such as a clamp. This could work well for a flexible bottle such as the one you are using, but would not generalize to a typical rigid container.
· You could use a source of compressed air to pressurize the bottle. For the purposes of this experiment, a low pressure, on the order of a few thousand Pascals (a few hudredths of an atmosphere) would suffice.
The means we will choose is the low-pressure source, which is readily available to every living land animal. We all need to regularly, several times a minute, increase and decrease the pressure in our lungs in order to breathe. We're going to take advantage of this capacity and simply blow a little air into the bottle.
· Caution: The pressure you will need to exert and the amount of air you will need to blow into the system will both be less than that required to blow up a typical toy balloon. However, if you have a physical condition that makes it inadvisable for you to do this, let the instructor know. There is an alternative way to pressurize the system.
You recall that it takes a pretty good squeeze to raise air 50 cm in the bottle. You will be surprised at how much easier it is to use your diaphragm to accomplish the same thing. If you open the 'pressure valve', which in this case consists of removing the terminating cap from the third tube, you can then use the vertical tube as a 'drinking straw' to draw water up into it. Most people can easily manage a 50 cm; however don't take this as a challenge. This isn't a test of how far you can raise the water.
Instructions follow:
· Before you put your mouth on the tube, make sure it's clean and make sure there's nothing in the bottle you wouldn't want to drink. The bottle and the end of the tube can be cleaned, and you can run a cleaner through the tube (rubbing alcohol works well to sterilize the tube). If you're careful you aren't likely to ingest anything, but of course you want the end of the tube to be clean.
· Once the system is clean, just do this. Pull water up into the tube. While maintaining the water at a certain height, replace the cap on the pressure-valve tube and think for a minute about what's going to happen when you remove the tube from your mouth. Also think about what, if anything, is going to happen to the length of the air column at the end of the pressure-indicating tube. Then go ahead and remove the tube from your mouth and watch what happens.
Describe below what happens and what you expected to happen. Also indicate why you think this happens.
****I expected the water to go back down in the bottle, which indeed happened. This is because when I take my mouth off the tube, air moved back in the bottle to equalize the pressure with the atmosphere.
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Now think about what will happen if you remove the cap from the pressure-valve tube. Will air escape from the system? Why would you or would you not expect it to do so?
Go ahead and remove the cap, and report your expectations and your observations below.
****I do not expect anything to happen because the pressure already equalizes when I removed my mouth from the tube. I was correct, nothing happened when I removed the cap.
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Now replace the cap on the pressure-valve tube and, while keeping an eye on the air column in the pressure-indicating tube, blow just a little air through the vertical tube, making some bubbles in the water inside the tube. Blow enough that the air column in the pressure-indicating tube moves a little, but not more than half a centimeter or so. Then remove the tube from your mouth, keeping an eye on the pressure-indicating tube and also on the vertical tube.
· What happens?
****When I blew into the tube making some bubbles, the water in the tube moved up. When I removed my mouth, the water did not move down.
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· Why did the length of the air column in the pressure-indicating tube change length when you blew air into the system? Did the air column move back to its original position when you removed the tube from your mouth? Did it move at all when you did so?
****The length of the air column changed because I added pressure while blowing into the tube. The air column did not move at all when I removed my mouth.
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· What happened in the vertical tube?
****The water level increased in the vertical tube.
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· Why did all these things happen? Which would would you have anticipated, and which would you not have anticipated?
****The water increased in the tube to try to maintain atmospheric pressure as more air was added, and I expected this to happen. I didn’t expect that the water level would stay the same after I blew bubbles and then removed my mouth from the tube.
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· What happened to the quantities P, V, n and T during various phases of this process?
****P increased, V remained constant, number of moles increased, and T probably changed in response to the changes in P and n.
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Place the thermometer that came with your kit near the bottle, with the bulb not touching any surface so that it is sure to measure the air temperature in the vicinity of the bottle and leave it alone until you need to read it.
Now you will blow enough air into the bottle to raise water in the vertical tube to a position a little ways above the top of the bottle.
· Use the pressure-valve tube to equalize the pressure once more with atmospheric (i.e., take the cap off). Measure the length of the air column in the pressure-indicating tube, and as you did before place a measuring device in the vicinity of the meniscus in this tube.Replace the cap on the pressure-valve tube and again blow a little bit of air into the bottle through the vertical tube. Remove the tube from your mouth and see how far the water column rises. Blow in a little more air and remove the tube from your mouth. Repeat until water has reached a level about 10 cm above the top of the bottle.
· Place the bottle in a pan, a bowl or a basin to catch the water you will soon pour over it.
· Secure the vertical tube in a vertical or nearly-vertical position.
The water column is now supported by excess pressure in the bottle. This excess pressure is between a few hundredths and a tenth of an atmosphere.
The pressure in the bottle is probably in the range from 103 kPa to 110 kPa, depending on your altitude above sea level and on how high you chose to make the water column. You are going to make a few estimates, using 100 kPa as the approximate round-number pressure in the bottle, and 300 K as the approximate round-number air temperature. Using these ball-park figures:
· If gas pressure in the bottle changed by 1%, by how many N/m^2 would it change?
****100kPa= 100,000N/m^2
(100,000 N/m^2)*(0.01) = 1000 N/m^2
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· What would be the corresponding change in the height of the supported air column?
****h= P/rho*g = (1000N/m^2)/[(1000kg/m^3)*(9.8m/s^2)] = 0.1m =10cm
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· By what percent would air temperature have to change to result in this change in pressure, assuming that the container volume remains constant?
****T would increase by 1%. #$&*
Continuing the above assumptions:
· How many degrees of temperature change would correspond to a 1% change in temperature?
****300K*0.01 = 3K. 300K+3K = 303K
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· How much pressure change would correspond to a 1 degree change in temperature?
****(1000N/m^2)/3= 333N/m^2
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· By how much would the vertical position of the water column change with a 1 degree change in temperature?
****h= P/(rho*g)= (1000N/m^2)/[1000kg/m^3 * 9.8m/s^2] = 0.01m = 10cm
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· How much temperature change would correspond to a 1 cm difference in the height of the column?
****P= rho*g*h = (1000kg/m^3)*(9.8m/s^2)*(0.01m) = 98N/m^2 = 98% increase
300K*0.98 = 294K change in temperature.
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@&
That's 98 N / m^2, not 98 kPa, which would be 98 000 Pa or 98 000 N/m^2.
*@
· How much temperature change would correspond to a 1 mm difference in the height of the column?
****P= (1000kg/m^3)*(9.8m/s^2)*(0.001m)= 9.8N/m^2
300K*0.098= 29.4K temperature change
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@&
98 Pa is about 0.1% of atmospheric pressure, not 10%.
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A change in temperature of 1 Kelvin or Celsius degree in the gas inside the container should correspond to a little more than a 3 cm change in the height of the water column. A change of 1 Fahrenheit degree should correspond to a little less than a 2 cm change in the height of the water column. Your results should be consistent with these figures; if not, keep the correct figures in mind as you make your observations.
The temperature in your room is not likely to be completely steady. You will first see whether this system reveals any temperature fluctuations:
· Make a mark, or fasten a small piece of clear tape, at the position of the water column.
· Observe, at 30-second intervals, the temperature on your alcohol thermometer and the height of the water column relative to the mark or tape (above the tape is positive, below the tape is negative).
· Try to estimate the temperatures on the alcohol thermometer to the nearest .1 degree, though you won't be completely accurate at this level of precision.
· Make these observations for 10 minutes.
Report in units of Celsius vs. cm your 20 water column position vs. temperature observations, in the form of a comma-delimited table below.
****
20.0 C, 32.5 cm
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.1, 32.5
20.1, 32.5
20.1, 32.5
20.1, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.0, 32.5
20.1, 32.5
20.1, 32.5
20.0, 32.5
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Describe the trend of temperature fluctuations. Also include an estimate (or if you prefer two estimates) based on both the alcohol thermometer and the 'bottle thermometer' the maximum deviation in temperature over the 10-minute period. Explain the basis for your estimate(s):
****The temperature fluctuations were very slight and appeared to be random. The deviation in the thermometer was 0.1 C, and their appeared to be no deviation in the ‘bottle thermometer’
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Now you will change the temperature of the gas in the system by a few degrees and observe the response of the vertical water column:
· Read the alcohol thermometer once more and note the reading.
· Pour a single cup of warm tap water over the sides of the bottle and note the water-column altitude relative to your tape, noting altitudes at 15-second intervals.
· Continue until you are reasonably sure that the temperature of the system has returned to room temperature and any fluctuations in the column height are again just the result of fluctuations in room temperature. However don't take data on this part for more than 10 minutes.
Report your results below:
****
45.2
42.9
40.6
38.0
36.8
35.8
35.1
34.6
34.0
33.7
33.3
32.9
32.7
32.5
32.5
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If your hands are cold, warm them for a minute in warm water. Then hold the palms of your hands very close to the walls of the container, being careful not to touch the walls. Keep your hands there for about a minute, and keep an eye on the air column.
Did your hands warm the air in the bottle measurably? If so, by how much? Give the basis for your answer:
****No, my hands did not measurably have an impact on the water in the column.
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Now reorient the vertical tube so that after rising out of the bottle the tube becomes horizontal. It's OK if some of the water in the tube leaks out during this process. What you want to achieve is an open horizontal tube,, about 30 cm above the level of water in the container, with the last few centimeters of the liquid in the horizontal portion of the tube and at least a foot of air between the meniscus and the end of the tube.
The system might look something like the picture below, but the tube running across the table would be more perfectly horizontal.
Place a piece of tape at the position of the vertical-tube meniscus (actually now the horizontal-tube meniscus). As you did earlier, observe the alcohol thermometer and the position of the meniscus at 30-second intervals, but this time for only 5 minutes. Report your results below in the same table format and using the same units you used previously:
****
20.0 C, 8.0 cm
20.0, 8.0
20.0, 8.0
20.0, 7.9
20.0, 7.9
19.9, 7.9
19.9, 7.9
19.9, 7.8
19.9, 7.8
19.9, 7.7
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Repeat the experiment with your warm hands near the bottle. Report below what you observe:
****Upon placing my warm hands near the bottle, the water quickly filled up the tube.
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When in the first bottle experiment you squeezed water into a horizontal section of the tube, how much additional pressure was required to move water along the horizontal section?
· By how much do you think the pressure in the bottle changed as the water moved along the horizontal tube?
****Very little force was required to move the water along the horizontal tube.
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· If the water moved 10 cm along the horizontal tube, whose inner diameter is about 3 millimeters, by how much would the volume of air inside the system change?
****V= pi*r^2*h= (3.1415)(0.0015m)^2*(0.1m) = 7.1*10^-7m^3= 0.71cm^3
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· By what percent would the volume of the air inside the container therefore change?
****>1%
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· Assuming constant pressure, how much change in temperature would be required to achieve this change in volume?
****>1%
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· If the air temperature inside the bottle was 600 K rather than about 300 K, how would your answer to the preceding question change?
****In this case, the required temperature change in the preceding question would double.
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There were also changes in volume when the water was rising and falling in the vertical tube. Why didn't we worry about the volume change of the air in that case? Would that have made a significant difference in our estimates of temperature change?
****We did not worry about the change in volume because it did not have a significant effect on the change in temperature. The water in the column was moving mainly because of the increased pressure from the increase in temperature.
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If the tube was not completely horizontal, would that affect our estimate of the temperature difference?
For example consider the tube in the picture below.
Suppose that in the process of moving 10 cm along the tube, the meniscus moves 6 cm in the vertical direction.
· By how much would the pressure of the gas have to change to increase the altitude of the water by 6 cm?
****P= rho*g*h = (1000kg/m^3)(9.8m/s^2)(0.06m) = 588N/m^2
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· Assuming a temperature in the neighborhood of 300 K, how much temperature change would be required, at constant volume, to achieve this pressure increase?
****(588N/m^2)/(100,000N/m^2)= 0.00588= 0.588%
300K*0.00588=1.76 degrees
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· The volume of the gas would change by the additional volume occupied by the water in the tube, in this case about .7 cm^3. Assuming that there are 3 liters of gas in the container, how much temperature change would be necessary to increase the gas volume by .7 cm^3?
****3L= 3000cm^3
0.7cm^3/3000cm^3= 2.3*10^-4= 0.023% change
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Continue to assume a temperature near 300 K and a volume near 3 liters:
· If the tube was in the completely vertical position, by how much would the position of the meniscus change as a result of a 1 degree temperature increase?
****1 K/300K= 0.33% change
3000cm^3*0.0033= 10cm^3
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· What would be the change if the tube at the position of the meniscus was perfectly horizontal? You may use the fact that the inside volume of a 10 cm length tube is .7 cm^3.
****
10cm/0.7cm^3= x cm/10cm^3. X= 143 cm change in length
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· A what slope do you think the change in the position of the meniscus would be half as much as your last result?
****I would assume that at a slope of 45 degrees, the change in meniscus position would be half as much as the last result.
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Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
· Approximately how long did it take you to complete this experiment?
4 hours
"
&#Good responses. See my notes and let me know if you have questions. &#