blondebombshell said:
hey all. i hav my bio prac exam on changing pH tomorrow. i need some help if possible coz im not exactly sure of what to do! i hav already looked around this site and found a bit of info but not too sure about how to go about it..thats all. if anyone could find some time to help me out by explainin a few things it would b much appreciated 
i kno i shouldnt leave it to the last minute but i did...dammit. The experiment is...demonstrate the effect of dissolved carbon dioxide on the pH of water. will b waitin... thanx muchly appreciated
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:
Word Equation:
Carbon dioxide + Water = Carbonic acid
Carbonic acid = Hydrogen + Bicarbonate
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="] [/FONT]safety goggles (compulsory, for safety purposes)
-[FONT="] [/FONT]1 small beaker
/test tube
-[FONT="] [/FONT]4 beakers
/test tubes of same size
-[FONT="] [/FONT]test tube rack (optional, only if using test tubes)
-[FONT="] [/FONT]measuring cylinder (ml)
-[FONT="] [/FONT]2 - 4 drinking straws (one for the lime water, second straw can be used for each of the distilled
/tap water (H2O))
-[FONT="] [/FONT]20 pieces pH paper (universal indicator paper)
/universal indicator liquid drops
-[FONT="] [/FONT]pH chart (universal indicator colour chart)
-[FONT="] [/FONT]data logger (optional, can be used in place of pH paper
/universal indicator liquid drops)
-[FONT="] [/FONT]timer
/stopwatch/watch
Materials
-[FONT="] [/FONT]100ml lime water (Ca(OH)2)
-[FONT="] [/FONT]100mL distilled
/tap water (H2O)
-[FONT="] [/FONT]carbon dioxide (CO2)
Method 1
1.[FONT="] [/FONT]A preliminary trial was carried out to determine if the method could be modified or improved upon.
2.[FONT="] [/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="] [/FONT]Place test tubes on test tube rack (optional, only if using test tubes).
4.[FONT="] [/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="] [/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="] [/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="] [/FONT]The beakers
/test tubes were labelled. 1-Control, 2-Test 1, 3-Test 2, 4-Test 3 respectively.
8.[FONT="] [/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="] [/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="] [/FONT]Beaker
/test tube 2 (Test 1) was blown into through a drinking straw over a period of 2 minutes.
11.[FONT="] [/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="] [/FONT]Steps 10 – 11 were repeated or replicated for beakers
/test tubes 3 and 4.
13.[FONT="] [/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.
[FONT="]
[/FONT]
Method 2
1.[FONT="] [/FONT]A preliminary trial was carried out to determine if the method could be modified or improved upon.
2.[FONT="] [/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="] [/FONT]Place test tubes on test tube rack (optional, only if using test tubes).
4.[FONT="] [/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="] [/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="] [/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="] [/FONT]The beakers
/test tubes were labelled. 1-Control, 2-Test 1, 3-Test 2, 4-Test 3 respectively.
8.[FONT="] [/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="] [/FONT]Beaker
/test tube 2 (Test 1) was blown into for 30 seconds through a drinking straw.
10.[FONT="] [/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="] [/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="] [/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="] [/FONT]The control was the first beaker
/test tube labelled ‘1-Control’ with the distilled
/tap water (H2O) that was left alone.
-[FONT="] [/FONT]The independent variable was the dissolved carbon dioxide concentrations (CO2) i.e. time spent blowing into the water.
-[FONT="] [/FONT]The dependent variable was the pH levels of the water.
-[FONT="] [/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.
[FONT="]
[/FONT]
Diagram
Risk Assessment
Results
[FONT="]
[/FONT]
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="] [/FONT]accurate measurement of variables
-[FONT="] [/FONT]appropriate use of equipment e.g. Measuring equipment i.e. measuring cylinder
-[FONT="] [/FONT]averaging of results
-[FONT="] [/FONT]controlled variables
Areas of reliability:
-[FONT="] [/FONT]control
-[FONT="] [/FONT]range of values for independent variable i.e. dissolved carbon dioxide concentration i.e. time spent on blowing into water
-[FONT="] [/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
