Your 'bottle thermometer' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** Your optional message or comment: **
** What happens when you pull water up into the vertical tube then remove the tube from your mouth? **
I was expecting the water to go back into the bottle, and it did as soon as i let my mouth off of the tube. This happened because there was not enough pressure in the tube to keep the water inside.
** What happens when you remove the pressure-release cap? **
Air did escape from the system, and the little bit of water that was left in the tube was pulled back into the bottle because there was not enough pressure inside of the bottle.
** What happened when you blew a little air into the bottle? **
the water stayed in the vertical tube after i removed my mouth from the tube.
the length of the air column in the pressure-indicating tube changed length when I blew air into the system because i was changing the temperature and pressure of the gas inside of the bottle.
All of these things happened because of the increased pressure entering the system and I did anticipate these things to happen.
** Your estimate of the pressure difference due to a 1% change in pressure, the corresponding change in water column height, and the required change in air temperature: **
it would change by 1 N/m^2
Im really not sure how to find the corresponding change in the height of the supported air columm, ive read the lectures and problems sets and im still not sure.
Would you use the ideal gas law? PV=nRT?
Assuming the original is atmospheric pressure, about 10^5 Pa or 10^5 N/m^2, then how much is 1% of the pressure? How high would a water column have to be to exert this much pressure at its base?
PV = n R T allows you to answer the question for temperature change.
** Your estimate of degrees of temperature change, amount of pressure change and change in vertical position of water column for 1% temperature change: **
** The temperature change corresponding to a 1 cm difference in water column height, and to a 1 mm change: **
** water column position (cm) vs. thermometer temperature (Celsius) **
Celsius vs. cm (the water in the column)
26.5 C 10.5 cm
26 C 10.5 cm
26 C 10.5 cm
26.5 C 10 cm
26.5 C 10 cm
26.5 C 10 cm
26 C 10 cm
26 C 10 cm
25.5 C 10 cm
25.5 C 10 cm
25.5 C 10 cm
25 C 9.8 cm
25 C 9.3 cm
25 C 9.3 cm
25 C 9.3 cm
25.2 C 9.3 cm
25.2 C 9.1 cm
25.2 C 9.1 cm
25 C 9 cm
25 C 9 cm
** Trend of temperatures; estimates of maximum deviation of temperature based on both air column and alcohol thermometer. **
The temperature seemed to stay pretty steady the whole time I was making observations. By the end of the 10 minutes, the temperature only changed at the most by one degree and the height of the water column pretty much stayed at the 10 cm that it was at originally. It did only go about 1.5 cm below the tape, but there was no significant change throughout the observations.
It appears that the water column height changed by about a centimeter per degree of temperature change.
** Water column heights after pouring warm water over the bottle: **
cm Celsius
35.5 C 30 cm
35.2 C 27 cm
35.2 C 23 cm
35 C 20.5 cm
34.5 C 19.6 cm
33.2 C 18.2 cm
33.2 C 17.9 cm
33 C 16.5 cm
33 C 16.2 cm
32.2 C 15.5 cm
31.6 C 14.8 cm
31 C 14 cm
30.5 C 13.6 cm
30.2 C 13.4 cm
30 C 12.8 cm
29.5 C 12.3 cm
28.8 C 11.7 cm
28.1 C 11.2 cm
27.8 C 10.9 cm
27.5 C 10.5 cm
27 C 10.2 cm
Here is looks like the change is about 2.5 cm per degree of temperature change. The greater range of temperature values and heights makes this result more reliable than the preceding.
How does this compare with the theoretical result predicted earlier?
** Response of the system to indirect thermal energy from your hands: **
when I held the palms of my hands very close to the walls of the container, the water in the vertical column rose up into the air column by about 3 centimeters.
** position of meniscus in horizontal tube vs. alcohol thermometer temperature at 30-second intervals **
Celsius cm
27 C 16.5 cm
27 C 16.5 cm
27 C 16.5 cm
27 C 16.4 cm
26.8 C 16.4 cm
26.8 C 16.3 cm
** What happened to the position of the meniscus in the horizontal tube when you held your warm hands near the container? **
The water in the horizontal water column moved very little, maybe a centimeter.
** Pressure change due to movement of water in horizonal tube, volume change due to 10 cm change in water position, percent change in air volume, change in temperature, difference if air started at 600 K: **
It didn't take much additional pressure because the water seemed to flow through the horizontal section on its own.
The volume of air inside the system would change
** Why weren't we concerned with changes in gas volume with the vertical tube? **
We didnt worry about the volume change in the air because there was not as much pressure in the system when the water was rising in falling in the vertical tube.
The key is that the vertical tube has very little volume; the volume change corresponding to a few cm of vertical height is insignifcant.
There could have been more of a temperature change if we added more pressure to the system
** Pressure change to raise water 6 cm, necessary temperature change in vicinity of 300 K, temperature change required to increase 3 L volume by .7 cm^3: **
im really not sure how to come up with these answers, i am having problems with the mathematical work in this lab, could you please help me? thanks!
How much pressure is exerted by water at a depth of 6 cm? This goes back to the early part of the introductory problem set.
The result can also be obtained by Bernoulli's equation; in this case all velocities are pretty much 0.
PV = n R T applies and allows you to determine temperature changes.
** The effect of a 1 degree temperature increase on the water column in a vertical tube, in a horizontal tube, and the slope required to halve the preceding result: **
** Optional additional comments and/or questions: **
about 3 hours
** **
i found this lab very confusing and i had to read it at least five times before i completely understood how to do the lab.
Good work on much of the lab. Your data are very good. However you need to work out a few of the techniques in the analysis, mostly related to the pressure required to support a water column, the connection with Bernoulli's equation, and the application of PV = n R T.
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