a longer or shorter time to change color.
Distance: 10 cm distance from solution in 250 ml beaker to the light bulb.
Throughout all the trials, a ruler is used to measure the distance between the light bulb to the solution in the beaker to be 10 cm.
A fixed distance of 10cm between light bulb and solution is present so wavelength of light penetrates solution with the same intensity throughout all trials of the same light bulb. This helps give a better, more reliable result for the concentration of vitamin C remaining after titration is carried out.
The volume of Ascorbic Acid:
55 ml initial volume
With the use of a volumetric cylinder, 55 ml of the ascorbic acid solution is
measured and then placed in a
250 ml beaker to be put under a specific light bulb at 900 lumens for 15 minutes.
The volume of the ascorbic acid controlled in order to obtain the concentration of ascorbic acid remaining after titration is complete. If initial volume is inconsistent for titrations, then
concentrations calculated would not be valid, hence cannot be comparable to remaining data.
Volume (2ml) of indicator
2,6-Dichlorophenolindophenol
(DCPIP)
The volume of indicator DCPIP is being controlled by using a 5ml syringe to measure 2 ml of the indicator.
The volume of indicator DCPIP must remain constant so it does not interfere with the range in the volume of ascorbic acid need to change DCPIP color from blue to clear and hence obtain a concentration for the ascorbic acid solution. If the volume of the indicator is not controlled, then the calculation for the concentration of ascorbic acid found in ascorbic acid solution under light manipulation will not be reliable.
The concentration of indicator
2,6-Dichlorophenolindophenol
(DCPIP)
The concentration of indicator
DCPIP will remain at 0.01M at every set volume of 2 ml placed in beaker below the titration apparatus.
A controlled concentration of indicator DCPIP would lead to
more reliable and coherent numbers when finding the volume of
ascorbic acid solution titrated into
0.01M DCPIP. If the concentration of DCPIP is not controlled, fluctuating volumes of ascorbic acid would be present. Making
volume difference (needed to find concentration using equation above) from titration reliable and hence could find an answer to the research question.
Materials and Apparatuses: Visual diagrams figure 1 and 2 were created using Google drawings
Materials used to create an ascorbic acid solution:
Instead of using fresh oranges and them for their my titrant, a more reliable alternative I found is referencing to natural hubs results from research conducted on the amount of vitamin C from different fruits. For an average size orange, according to Natural hub, it contains 70 mg of vitamin C (Uhis 4). Hence, using basic conversion learned, I made sure that every sample of 55 mL from my 1 L solution of ascorbic acid to contain 70 mg or 0.07g of ascorbic acid powder to mimic the amount of vitamin C present in orange for every 55 mL trial instead of using fresh squeezed orange juice.
Materials need to create vitamin C solution are:
● 1 L of distilled water
● 1.27 g of ascorbic acid (Vitamin C) crystalline powder
To determine the new concentration of vitamin C remaining after duration under the specific light bulb, the use of the concentration formula is required.
(n) mols of vitamin C in an orange (found from online source (naturalhub.com) )
C =
(V ) F inal volume − Initial volume of titration of vitamin C source
n = (m) Mass (g) = 0.07g = 3.97 × 10 −4moles of vitamin C in an orange
(Mr) Molar Mass of ascorbic acid (C 6 H 8 O 6) (g/mol)
New concentration formula would be:
−4
176.12g/mol
3.97 ×10 mols
C = (1000)
(V ) F inal volume(mL) − Initial volume of titration of vitamin C(mL)
Materials used to create a 0.01M solution of indicator dichlorophenolindophenol (DCPIP):
● 0.68 g of 1g DCPIP concentrate
● 200 ml of distilled water
Safety:
Ascorbic Acid (Vitamin C): Adapted from (Global Safety management)
Lab Safety: When handling pure ascorbic acid powder, gloves and safety goggles are required as may cause irritation to skin and eyes.
Disposal: A solution of ascorbic acid is non-hazardous, hence it can be easily disposed of down a drain.
DCPIP indicator:
Health Hazard:
Hazard Risk How can it be minimized
Level of risk
0.01M DCPIP solution Irritation and dryness of skin
Wear gloves and safety goggles
Medium
Disposal: Due to the minimal amounts used in my investigation, after its use, simply dilute it more making it safe to drain down the sink. However, if used in greater amounts, it should be issued to a chemical disposer.
Methodology:
Preparation of ascorbic acid solution and 0.01M indicator DCPIP (Dichlorophenolindophenol) solution
1. Using a scale, measure out 1.27g of ascorbic acid powder and place it in 1 L of distilled water. a. Using a magnetic stirrer, stir in ascorbic acid for a minute in a dim setting as light does
affect the abundance of ascorbic acid present.
2. Using a scale, measure 0.68 g of DCPIP concentrate and place it in 200 ml of distilled water.
a. Place magnetic stirrer in DCPIP solution and still for a minute to ensure the mix of the solution.
Procedure:
1. Prepare the titration apparatus as shown in figure 1.
2. Place a sample of 1L of ascorbic acid solution in a 250 ml beaker and cover the rest of the solution with a paper bag or store in a dim area to avoid much decrease in vitamin C abundance.
3. Using a 100ml graduated cylinder, measure 55 ml of ascorbic acid solution from the sample in the beaker and place it in a clean 250 ml beaker.
a. The first 55 mL of ascorbic acid solution will directly be titrated. This is done to obtain an initial concentration value in order to compare upcoming results influenced by light.
4. Make sure burette knob of the titration apparatus is closed and then pour the 55 ml of ascorbic acid solution in the burette. Take the initial volume shown from the titration burette.
5. Place a sample of indicator DCPIP solution in a 250mL beaker to avoid contamination of whole
DCPIP solution.
a. Using the 5 ml syringe take 2 ml from a sample collected of DCPIP solution and place it in a 250 ml beaker that it's under the titration burette.
b. Place a white sheet of paper under the 250 ml beaker containing the 2ml DCPIP solution as this will help see when the color change and concentration of vitamin C are found.
6. Twist the burette knob to control the amount of ascorbic acid released causing color changes;
make sure color reaches that shown in figure 5, transparent color.
a. Once the color has become transparent, twist the knob shut and take note of the final volume of ascorbic acid shown on the burette.
7. Once initial concentration is found by titrating 55 ml of ascorbic acid solution in 2 ml of 0.01M of DCPIP, it's time to find the influence of different lights fluorescent, led and incandescent at 900 lumens have on the ascorbic acid solution.
8. Screw in an incandescent light bulb at 60 watts into lampstand and place the beaker with 55 ml sample of ascorbic acid under lampstand.
9. Using 20 cm ruler, ensure that the distance between incandescent light bulb and solution is 10 cm.
10. Set the timer to 15 minutes and turn on the incandescent light bulb.
11. When 15 minutes are over, place the 55 ml sample of ascorbic acid into the titration burette and titrate as instructed in step 6.
12. Repeat steps 8 to 11 four more times for incandescent light bulbs to obtain 5 trials
13. Repeat steps 3-12 for 55 ml of the Ascorbic acid solution under fluorescent and LED light bulbs.
Data Collection:
Qualitative data:
- When 55 mL sample was put under incandescent light for 15 minutes with 10 cm distance from the light bulb to the ascorbic acid solution, it was noticed that the light bulb heated. This caused the vitamin C solution to heat up. On the other hand, remaining light bulbs fluorescent and led did not heat up the solution.
- When adding the ascorbic acid solution into the 2 ml of 0.01M DCPIP, it was noticed that the color blue turns into a brownish red color and finally clear. When the solution is colorless, this indicates that the correct volume of ascorbic acid solution is added to and the concentration of specific trial can be found by getting the volume difference.
*images below are taken by my iPhone showing the change in color of 0.01M DCPIP
solution as 55mL of the light-manipulated ascorbic acid solution is added.
Before any 55mL of the ascorbic acid solution is added to 2 ml of
0.01M of DCPIP
As the 55mL of the ascorbic acid solution is being titrated into 2 ml of
0.01M of DCPIP
When enough volume of the 55 mL of ascorbic acid is titrated into 2 ml of 0.01M of DCPIP
Figure 3 Figure 4 Figure 5
- It was observed that titration of ascorbic acid that was placed under fluorescent light for 15 minutes in 10 cm distance from the bulb to solution took the least time for the change in color from blue to brownish red and finally to clear.
- It was observed that titration of ascorbic acid that was placed under incandescent light for 15 minutes in 10 cm distance from the bulb to solution took the longest for the change in color from blue to brownish red to clear.
Raw and Processed Quantitative Data:
Table 1: Raw and Processed Data of Ascorbic Acid Titration into DCPIP
T he initial concentration of the ascorbic acid solution under no manipulation of any light :
−4
C = 3.97 ×10 mols (1000) =
F inal volume (mL) − Initial volume of titration of vitamin C(mL)
3.97 ×10= −4 moles (1000) = 0.173 moles /L
2.3×10 −6mL
Concentration Of
Types Of
Light
Trials
Initial Volume
(±0.05 mL)
Final Volume (±0.05 mL)
Volume Difference (±0.05 mL)
Ascorbic Acid After exposure to light at
900 lumens for 15 minutes (±0.01 moles/
L)
*Average Concentration (±0.01 moles/ L)
*Standard
Deviation
Fluorescent
LED
Incandescent
1 12.2 19.5 7.3 *0.054
2 12.5 20.0 7.5 0.053
3 13.7 21.2 7.5 0.053
4 13.5 23.3 9.8 0.041
5 12.7 29.4 9.7 0.041
1 13.9 23.3 9.4 0.042
2 12.0 21.1 9.1 0.044
3 13.4 22.3 8.9 0.045
4 13.6 23.0 9.0 0.044
5 13.5 22.5 9.5 0.042
1 13.7 25.5 11.8 0.034
2 13.6 26 12.4 0.032
3 13.6 27.5 13.9 0.029
4 12.2 26 13.8 0.029
5 13.4 27 13.9 0.029
*0.048 *0.007
0.043 0.001
0.031 0.002
It can be noticed that all concentrations obtained at all light sources are significantly smaller than the initial concentration of the ascorbic acid solution under no light influence.
*Sample Calculation to obtain the concentration of ascorbic acid after exposure to light ar 900 lumen for
15 minutes
C = n(moles) (1000) = 3.97 ×10 −4 mols (1000)
V olume Difference (ml)
3.97 ×10 −4 moles
F inal volume (mL) − Initial volume of titration of vitamin C(mL)
= 19.5−12.2
(1000) = 0.054 moles/L ± 0.01moles/L
Concentration formula multiplied by 1000 in order for units to be moles per L.
* Average concentration calculated using Microsoft Excel with formula
Concentration of vitamin C T rial 1+ trial 2+ trial 3+trial 4+trial 5
=
5
0.054+0.053+0.053+0.041+0.041
5
= 0.048 moles/L
± 0.01moles/L
*Standard Deviation Calculated using Microsoft Excel with the formula: STDEV(Trial 1: Trial 5) for each light type
Figure 6: Histogram created using google sheets by data obtained from Table 1 above
The following histogram indicates that fluorescent light at 900 lumens obtains the greatest average concentration (0.05 moles/ L) of ascorbic acid at a duration of 15 minutes, this is further supported as it took the least amount of time for color of indicator 2 ml 0.01M DCPIP to change from dark blue to brownish red and finally clear liquid when performing the titration. Led light has the second greatest average concentration (0.04 moles/L) of ascorbic acid under the same conditions stated for that of fluorescent light. Lastly, incandescent has the lowest concentration (0.03 moles/L) of ascorbic acid also under the same duration of 15 minutes. When performing the titration, it was observed that ascorbic acid under influence of incandescent light took the longest time to change indicator 0.01M DPIP blue solution from blue to brownish red and finally clear better shown in figure 3 to 5. The results on the histogram above are shown through a gradual decrease from Fluorescent, LED and Incandescent light. In addition, error bars on each bar indicate the reliability and accuracy of calculated concentrations. The fluorescent light at 900 lumens in blue obtains the greatest error bar with a standard deviation of 0.007. This indicates that data obtained may be altered due to consequences of mal-calculation or human error while
conducting titration and recording its data. The error bar of the incandescent light at 900 lumens in
yellow obtains the second greatest error bar with a standard deviation of 0.002, indicating that less error in collecting the data and conducting the titration had occurred. Finally, the error bar of LED light at 900 lumens in red has the smallest error bar with a standard deviation of 0.001, indicating that an accurate titration took place and data collected was the most accurate.
The average concentration of vitamin C under all types of light (Fluorescent, Incandescent and LED) have all decreased by no less than 50 % of its original concentration of 0.173 moles /L calculated in raw and
processed data collection section; indicating that light has a great effect on the concentration of vitamin C
present.
The research question posed at the commencement of this investigation can be answered is that light sources LED, Incandescent and Fluorescent at light intensities of 900 lumens all affect the initial
concentration of orange ( 0.173 moles /L
± 0.01moles/ L ). In addition, the hypothesis posed at the
beginning of the investigation is that Incandescent Light would have the most effect on vitamin C concentration in oranges is accepted. Data obtained suggest that incandescent light at 900 lumens effects concentration of oranges the most, hence is the worst light for oranges to be stored and maintained at. Therefore, to maintain the effectiveness of oranges as a metabolic booster, they should be stored under fluorescent light as they according to data collect seem to have the least effect on vitamin C
concentration. However, due to the fluorescent light error bar in figure 6 being the greatest of three lights, this may not be the most efficient light oranges should be stored at. The reason for fluorescents error bar is discussed in limitations and weaknesses below. A statistical test is carried out below to identify if the reason of this error bar is due to any human error
Statistical Test:
The ANOVA statistical test will be conducted for this investigation to find if any statistical difference is present accepting a correlation between the type of light bulb to concentration of vitamin C. This test was chosen as more than two independent unrelated variables are chosen which are incandescent light at 900 lumens, LED light at 900 lumens and finally, fluorescent light at 900 lumens. The following is the ANOVA statistical test formula- the image was taken from (Statsdirect.com):
This formula has been processed with the significance level of 0.05 which indicates that if p-value obtained from the calculation is less than 0.05 ( p =< 0.05 ), hence 95% would reject H0 and accept H1. In addition, it would signify the correlation between different light types and concentration of vitamin C. The statistical results for this investigation below are courtesy of One- Way ANOVA calculator (Stangroom). The f- ratio value is 23.9, and the p-value came to be
0.000065, which is less the 0.05 meaning that results are significant
and different light types do have an effect on the vitamin C present in oranges and data and observation portraying that are not due to human error.
Evaluation:
The strength of this investigation includes the number of controlled variables that increase the reliability of the results obtained. Some include the controlled distance between the light bulb and ascorbic acid solution always being a difference of 10cm among all trials for al different light types. In addition, having all light types used in this investigation at 900 lumens aided in the reliability of data collected. Lumens
are the quantity of light emitted by the specific light source, hence controlling that ensures the same amount of light is hitting the ascorbic acid solution for 15 minutes which leaves the concentration of ascorbic acid solution the only changing factor. Furthermore, the use of titration method to find the concentration of the ascorbic acid solution assures accuracy in numbers obtained. The ascorbic acid solution in this investigation models the ascorbic acid content present in orange.
Limitations or Weakness Effects on results Suggestions for improvement
I relied on my eyesight to figure out if, in fact, 50 ml of ascorbic acid was measured out into the 250mL beaker to be later
transferred into the titration burette for every titration trial.
This is a systematic error as it can affect the accuracy of volume needed to change indicator DCPIP and identify the concentration of vitamin C --
Not reading meniscus at a perpendicular angle at all times led to the great fluctuation of data shown in volume difference and concentration of vitamin C
found in orange in data collected for fluorescent light. Hence, data for incandescent light had the greatest standard deviation of
0.007, therefore the greatest error bar.
- Have 7 trials instead of 5 trials which will help minimize systematic errors by a getting more accurate readings of 50 ml ascorbic acid solution in a beaker, hence more accurate titration trials and less uncertainty should take place.
- A statistical test can be carried out to show if this systematic error has greatly affected the results obtained.
Even though efforts were made to cover up the liter of ascorbic acid solution from surrounding light by a paper bag when not used, the ascorbic acid solution was still affected by surrounding light when taken out to measure 50 ml and when sitting in
titration burette.
This is a human error
Having a non-controlled light source like the surrounding light of the lab on the initial ascorbic acid solution, may affect the concentration of ascorbic acid even before inserting it in controlled light conditions from the independent variables.
This ultimately affects the resulting concentration of ascorbic acid after titration and the reliability of data collection.
- Carry out the investigation in dimmer settings to obtain data with fewer errors.
- Perform this experiment efficiently, therefore the solution of ascorbic acid remains at its theoretical concentration before its manipulation by independent variables.
Ideas for Further Investigation:
With the information gained from this experiment, further research could be done to not only test the light source at which oranges are stored at but the temperatures they as stored at as well. Oranges are usually kept in refrigerators at cold temperatures, I wonder if temperature plays a role in the effectiveness of vitamin C in oranges or another vitamin C rich fruits. As seen in the process of this investigation, Vitamin C is greatly affected by temperature and light; hence, an experiment could be done to obtain the best temperature at which oranges should be stored to maintain the vitamin C content. An experimental lab posted on UKessays tests the temperature effect of vitamin C in orange juice can be adapted and conducted to measure the concentration of vitamin C remain after influence by different temperatures (independent variables) and this would be found by the use of a titration. Not only the concentration of Vitamin C in oranges can be tested, but other citrus fruits in order to test which fruit would hold on to the concentration of vitamin C better. This would indicate which citrus fruit is the best for an increase in metabolic activity.
Works Cited
Division, The Lighting. “LED FAQ's.” LED Lighting, www.thelightingdivision.com/led_faq.html. Fielder, J. “Spectroscopy.”
Uhis. “Natural Food-Fruit Vitamin C Content.” The Vitamin C Content of Fruit of the World., www.naturalhub.com/natural_food_guide_fruit_vitamin_c.htm.
R, Nave. “Fluorescent Lighting.” Total Internal Reflection, hyperphysics.phy-astr.gsu.edu/hbase/electric/lighting.html.
Direct, Stats. “One Way Analysis of Variance.” One Way Analysis of Variance, www.statsdirect.com/help/analysis_of_variance/one_way.htm. ANOVA formula
Stangroom, Jermey. “One-Way ANOVA Calculator.” Social Science Statistics, www.socscistatistics.com/tests/anova/default2.aspx. ANOVA value calculated
Safety Management, Global. “Safety Data Sheet.”
Https://Beta-Static.fishersci.com/Content/Dam/Fishersci/en_US/Documents/Programs/Education/Regulat ory-Documents/Sds/Chemicals/Chemicals-a/S25184.Pdf, 2015,
beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-docume nts/sds/chemicals/chemicals-a/S25184.pdf.
Tables, Rapid. “How to Convert Lumens to Watts.” KWh to Watts (W) Conversion Calculator, www.rapidtables.com/calc/light/how-lumen-to-watt.html.
Sinha, Anjan. (2014). Studies on Ascorbic Acid (Vitamin-C) Content in Different Citrus Fruits and its
Degradation During Storage. Science and culture. 80. 265-268.
"Effect of Temperature on Vitamin C in Orange Juice." UKEssays.com. 11 2018. All Answers Ltd. 02
2019
<https://www.ukessays.com/essays/biology/degradation-of-vitamin-c-in-orange-fruits-biology-essay.php?
vref=1>.
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rkaakiacsedulb (student)
