Help on practical exam (1 Viewer)

[M'broughRockz]

anyone know anything about the experiment on "the effect of dissolved carbon dioxide on the Ph of water". Like wat to expect, background info etc. (hints?)

 

[white_spazzy]

lol this is like the easiest experiment.

ours involved....distilled water in a beaker, a straw, a blowing into the water, and universal indicator.
Main point of the experiment: carbon dioxide lowers the pH of water

hope that helps

 

[Michiru]

haha. yep basically like white_spazzy said.

method
1. fill a beaker with 200mL of water
2. test the ph of the water with a pH probe or similar devices
3. use a straw to blow into it for 6 min
4. measure the pH of water again

REsults
you should except a very slight decrease in pH. this is becuz carbon dioxide dissolves not very easily into water. (instead of using water, you teacher may use lime water)

the equation is CO2 + H20 <-> H2CO3
<-> is meant to be an equilibrium arrow

wat does this experiment demonstrate?
it shows how carbon dioxide dissolved in blood plasma (which contains water) makes the blood acidic (which it bad X]

yea...i hope i make sense and all that helped.

 

[M'broughRockz]

yeah, this helped heaps. Thnx. I was wondering wat the control, independant and dependant variables would be?

 

[white_spazzy]

yeah, this helped heaps. Thnx. I was wondering wat the control, independant and dependant variables would be?

okay ill have to give u the method i used, to demonstrate the control, independant and dependant variables.

Method:

1. Set up 5 beakers with 50mLs of distilled water (pH 7)
2. Label all test tubes with a number 1 through to 5
3. Beaker 1 will be the CONTROL. do not blow any carbon dioxide into the water, test the water with universal indicator paper. Record the colour displayed in a table.
4. Blow into test tube 2 for 2 minutes. Test the pH with universal indicator paper. Record the result in your table.
5. Repeat step 4 with all beakers, increasing the amount of time blown into each tube by 2 minutes each beaker. (eg- B2=2mins, B3=4mins etc)
6. Once all results are recorded, repeat the experiment twice more to ensure the reliablilty of all results.

okay so by this experiment the control was Beaker 1: that was not affected by carbon dioxide and should have illustrated a neutral pH
independant: would be the amount of time that u blow into the beaker
Dependant: the pH of the water/ the colour of the UI Paper after being put into the water.

i did this ages ago so i hoe that its right.

 

[M'broughRockz]

thnx due. By any chance do u still have the booklet u recieved wen doing the expt?

 

[white_spazzy]

nah sorry, we had to design our own experiment for this one

 

[duckofdoom]

always make sure that when you're writing your experiment you mention using universal indicator to measure the ph or a ph level. Also mention a ph level's unreliability as they tend to sway by a fraction. This is what our teacher told us.

There's excellent methods above.

Also remember the safety component. How you'd change the expt. to be safer.

Mention not to swallow the liquid, spill it everywhere etc. They always give a few extra marks when you include that.

 

[Lisa88]

thanks

thanks heaps...we r doing that bio prac on tues....u dont hapen to have any info from
-analyse information .....identify current technologies.........allow measurement of oxygen saturation and co2 concentrations in blood....
-gather,process, and analyse info fron 2ndary sources.....compare the process of renal dialysis and the function of the kidney and explain 1 relationship between a bioscopic process and a macroscopic process

 

[Kirika]

the current technologies are arterial blood gas analysis machines and another one that i cant remember but uses light to detect the colour of your blood and hence its oxygen saturation. with the dialysis its pretty simple, a table comparison is good if it doesnt need to be detailed, but go on how it is done, what it uses, active/passive and effectiveness and time. its also worth mentioning that you can have renal and peritoneal dialysis, but its not essential if you run out of time. there is heaps of dialysis info on the net and there should be a heap in your text. also try the HSC online site it has a small table and links to sites like the kidney foundation and stuff like that.

 

[kow_dude]

the current technologies are arterial blood gas analysis machines and another one that i cant remember but uses light to detect the colour of your blood and hence its oxygen saturation.

The other technology is an Oximeter. A clip clips onto your finger and passes through light. The more oxygen saturated in your blood, the brighter the red is.

In regards to the prac, i think the idea of using a straw and blowing into the water is silly. You should use the reaction between calcium carbonate and hydrochloric acid to produce carbon dioxide:

calcium carbonate + hydrochloric acid —> calcium chloride + water + carbon dioxide

The end result becomes more obvious.

 

[jagshemesh]

anyone know anything about the experiment on "the effect of dissolved carbon dioxide on the Ph of water". Like wat to expect, background info etc. (hints?)

Background Information
Carbon dioxide (CO2) is produced in living organisms as a result of cellular respiration. When carbon dioxide (CO2) dissolves in water (H2O) it forms carbonic acid (H2CO3), which is toxic to cells. All organisms get rid of carbon dioxide (CO2) as quickly as possible before it can interfere with the chemical activities of cells.

Mammals breathe out carbon dioxide (CO2) from their lungs. This can be demonstrated using lime water (Ca(OH)2). Carbon dioxide (CO2) turns lime water (Ca(OH)2) milky.

Equation:

CO2 + H2O <=> H2CO3​

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H2CO3 <=> H+ + HCO3-​

Word Equation:

Carbon dioxide + Water = Carbonic acid​

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Carbonic acid = Hydrogen + Bicarbonate​

Hypothesis
Dissolved Carbon Dioxide (CO2) in water (H2O) affects the pH level. Therefore dissolved carbon dioxide (CO2) decreases the pH of water (H2O).


Aim/Purpose
To design or plan, choose equipment and materials, conduct and report on an investigation experiment that investigates and demonstrates the effect of dissolved carbon dioxide (CO2) on the pH of water (H2O).


Objective
To test the hypothesis stated above that dissolved carbon dioxide (CO2) decreases the pH level of water (H2O).


Equipment
-[FONT=&quot] [/FONT]safety goggles (compulsory, for safety purposes)
-[FONT=&quot] [/FONT]1 small beaker/test tube
-[FONT=&quot] [/FONT]4 beakers/test tubes of same size
-[FONT=&quot] [/FONT]test tube rack (optional, only if using test tubes)
-[FONT=&quot] [/FONT]measuring cylinder (ml)
-[FONT=&quot] [/FONT]2 - 4 drinking straws (one for the lime water, second straw can be used for each of the distilled/tap water (H2O))
-[FONT=&quot] [/FONT]20 pieces pH paper (universal indicator paper)/universal indicator liquid drops
-[FONT=&quot] [/FONT]pH chart (universal indicator colour chart)
-[FONT=&quot] [/FONT]data logger (optional, can be used in place of pH paper/universal indicator liquid drops)
-[FONT=&quot] [/FONT]timer/stopwatch/watch


Materials
-[FONT=&quot] [/FONT]100ml lime water (Ca(OH)2)
-[FONT=&quot] [/FONT]100mL distilled/tap water (H2O)
-[FONT=&quot] [/FONT]carbon dioxide (CO2)


Method 1
1.[FONT=&quot] [/FONT]A preliminary trial was carried out to determine if the method could be modified or improved upon.
2.[FONT=&quot] [/FONT]Safety goggles were put on to prevent splashing of the lime water (Ca(OH)2) ordistilled/tap water (H2O) into the eyes.
3.[FONT=&quot] [/FONT]Place test tubes on test tube rack (optional, only if using test tubes).
4.[FONT=&quot] [/FONT]100mL of lime water (Ca(OH)2) was measured using a measuring cylinder and poured into the small beaker/test tube (10ml for test tube).
5.[FONT=&quot] [/FONT]The lime water (Ca(OH)2) was blown into through a drinking straw. This will demonstrate that an exhaled breath contains carbon dioxide (CO2) when it turns a milky texture.
6.[FONT=&quot] [/FONT]100mL of distilled/tap water (H2O) was measured using a measuring cylinder and poured into a beaker (10ml for test tubes). This was repeatedor replicated for beakers/test tubes 3 and 4.
7.[FONT=&quot] [/FONT]The beakers/test tubes were labelled. 1-Control, 2-Test 1, 3-Test 2, 4-Test 3 respectively.
8.[FONT=&quot] [/FONT]The pH level of all 4 beakers was tested using pH paper and compared to a pH chart and the results were recorded.
9.[FONT=&quot] [/FONT]Beaker/test tube 1 (Control) was left to sit and the pH level tested and recorded after 30 secs, 1 min, 1 min 30 secs, and 2 mins.
10.[FONT=&quot] [/FONT]Beaker/test tube 2 (Test 1) was blown into through a drinking straw over a period of 2 minutes.
11.[FONT=&quot] [/FONT]The pH level of the distilled/tap water (H2O) was tested after 30 secs, 1 min, 1 min 30 secs, and 2 mins and recorded.
12.[FONT=&quot] [/FONT]Steps 10 – 11 were repeated or replicated for beakers/test tubes 3 and 4.
13.[FONT=&quot] [/FONT]After experimenting, the lime water (Ca(OH)2) and water (H2O) was disposed of down the sink and all equipment was either washed or thrown out.










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[/FONT]

Method 2
1.[FONT=&quot] [/FONT]A preliminary trial was carried out to determine if the method could be modified or improved upon.
2.[FONT=&quot] [/FONT]Safety goggles were put on to prevent splashing of the lime water (Ca(OH)2) ordistilled/tap water (H2O) into the eyes.
3.[FONT=&quot] [/FONT]Place test tubes on test tube rack (optional, only if using test tubes).
4.[FONT=&quot] [/FONT]100mL of lime water (Ca(OH)2) was measured using a measuring cylinder and poured into the small beaker (10ml for test tube).
5.[FONT=&quot] [/FONT]The lime water (Ca(OH)2) was blown into through a drinking straw. This will demonstrate that an exhaled breath contains carbon dioxide (CO2) when it turns a milky texture.
6.[FONT=&quot] [/FONT]100mL of distilled/tap water (H2O) was measured using a measuring cylinder and poured into a beaker (10ml for test tubes). This was repeated or replicated for beakers/test tubes 3 and 4.
7.[FONT=&quot] [/FONT]The beakers/test tubes were labelled. 1-Control, 2-Test 1, 3-Test 2, 4-Test 3 respectively.
8.[FONT=&quot] [/FONT]Beaker/test tube 1 (Control) was added with one full drop of universal indicator liquid drops and the pH level was recorded using the pH chart.
9.[FONT=&quot] [/FONT]Beaker/test tube 2 (Test 1) was blown into for 30 seconds through a drinking straw.
10.[FONT=&quot] [/FONT]Beaker/test tube 2 (Test 1) was added with one full drop of universal indicator liquid drops and the pH level was recorded using the pH chart.
11.[FONT=&quot] [/FONT]Steps 10 – 11 were repeated or replicated for beakers/test tubes 3 and 4, adding 30 seconds of blowing to each beaker/test tube than the previous beaker/test tube each time.
12.[FONT=&quot] [/FONT]After experimenting, the lime water (Ca(OH)2) and water (H2O) was disposed of down the sink and all equipment was washed or thrown out.

Variables:
-[FONT=&quot] [/FONT]The control was the first beaker/test tube labelled ‘1-Control’ with the distilled/tap water (H2O) that was left alone.
-[FONT=&quot] [/FONT]The independent variable was the dissolved carbon dioxide concentrations (CO2) i.e. time spent blowing into the water.
-[FONT=&quot] [/FONT]The dependent variable was the pH levels of the water.
-[FONT=&quot] [/FONT]The controlled variables were the type of water, size of cup, amount of water, type of pH paper and chart and size of drinking straw used. These were controlled by keeping them constant for each test.








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Diagram

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Risk Assessment






Results

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Discussion

The results of this experiment supported the hypothesis that dissolved carbon dioxide (CO2) decreases the pH of water (H2O). The trend shown by the results is that the pH of the water (H2O) decreased with the more time spent breathing into it. The more dissolved carbon dioxide (CO2) in the water (H2O), the lower the pH. This was demonstrated in all three tests.

A preliminary trial was carried out before the experiment was done to identify any possible problems in the method. The trial showed that the method was appropriate and had no major flaws however it showed that the blowing must be done carefully to avoid the water (H2O) splashing out of the cup.

This investigation can be considered reliable as the method was repeated three times. The results from the three tests were all very similar and were consistent with the information gathered from reputable sources. It can also be concluded that the investigation is valid because the findings relate directly to the hypothesis and the question posed by the assignment. The procedure tested the hypothesis that it was designed to and the controlled variables were strictly controlled. Thus, the information was gathered in a valid way.

The experiment was accurate and no major errors were encountered. However, it was not carried out in a scientific environment with specifically scientific equipment. As household items were used and not scientific equipment, this could have been a source of error, especially in measurement. Also, distilled/tap water (H2O) was used, and although the pH of the water (H2O) of all three trials was the same, the minerals in the water (H2O) may have varied and this could have affected the experiment. If the experiment was repeated again, it could be done in a scientific environment with scientific equipment, including using a data logger with a pH probe instead of pH paper and chart. Use of distilled water (H2O) also improves the accuracy of the results observed and recorded.

These results were supported by the information already gathered. Reliable data states that excess carbon dioxide (CO2) dissolved in the blood plasma reacts with the water (H2O) in the plasma and forms carbonic acid (H2CO3) and lowers the pH of the blood. The fact that dissolved carbon dioxide (CO2) in the body lowers the pH of the blood is important for many reasons. Metabolic functions can only take place during a very specific pH level. Normal blood pH is 7.4. When this level is too high or low, enzyme activity is affected and may ultimately stop, causing the cell to die. Too much carbon dioxide (CO2) in the blood increases the level of carbonic acid (H2CO3), which in turn increases the number of bicarbonate (HCO3) and hydrogen (H) ions. This decreases the pH, which decreases the oxygen (O) saturation of haemoglobin, meaning the blood cannot carry as much oxygen (O) around the body. Dissolved carbon dioxide (CO2) and bicarbonate (HCO3) ions are also important to the body as they help to maintain the normal pH level of the blood.

This information is also important for aquatic organisms. Different organisms can only survive within a certain range of pH levels. If the level of carbon dioxide


(CO2) in the water (H2O) of their environment is higher or lower than normal it will change the pH level. If this pH level is too high or too low it could deform the enzymes of the organism and affect the enzyme activity. This would put the organism under stress and could cause death. This is also important to people who keep fish or other aquatic organisms as pets as they would need to control the dissolved carbon dioxide (CO2) level.

The effect of dissolved carbon dioxide (CO2) on the pH of water (H2O) is also important in the use of tests such as the arterial blood gas test. This is a test where levels of carbon dioxide (CO2) and oxygen (O) in the body are tested among other things. The arterial blood gas test measures the pH level of the blood and also the concentration of Bicarbonate (HCO3) ions. The level of dissolved carbon dioxide (CO2) in the body directly affects these two factors. This test is important in medicine as it can indicate problems with the lungs, heart, kidneys and metabolism.

Research in this area could be directed in the future into using the fact that dissolved carbon dioxide (CO2) in water (H2O) lowers the pH level for other purposes. For example: in the growing of grasses for golf courses, etc. or the breeding of aquatic species. Also, the effect of the carbon dioxide (CO2) in the atmosphere could be researched more in relation to acid rain in the climate of both past eras and the present.

Areas of accuracy:
-[FONT=&quot] [/FONT]accurate measurement of variables
-[FONT=&quot] [/FONT]appropriate use of equipment e.g. Measuring equipment i.e. measuring cylinder
-[FONT=&quot] [/FONT]averaging of results
-[FONT=&quot] [/FONT]controlled variables

Areas of reliability:
-[FONT=&quot] [/FONT]control
-[FONT=&quot] [/FONT]range of values for independent variable i.e. dissolved carbon dioxide concentration i.e. time spent on blowing into water
-[FONT=&quot] [/FONT]repetition or replication


Conclusion
An investigation experiment that investigated and demonstrated the effect of dissolved carbon dioxide (CO2) on the pH of water (H2O) was planned, designed, choose equipment and materials, conducted reported on. The hypothesis that dissolved carbon dioxide (CO2) decreases the pH of water (H2O) was proven to be correct.

PS: If any corrections need to be made or if there are any new suggestions please make a reply post.

PPS: For the full document please go the the URL link below or dowload the attatched typed Microsoft Word document.

URL Link Source: http://boredofstudies.org/view.php?course=10#10.1
by Kat S

Thanks
Jagshemesh