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Comparison of Vitamin C in Juice Drinks Mark as Favorite (2 Favorites)

LESSON PLAN in Chemical Change, Chemical Change, Concentration, Titrations, Indicators, Accuracy, Equivalence Point, Error Analysis. Last updated May 16, 2024.


In this lesson, students will use a color-changing indicator called indophenol and a simplified titration method to determine if vitamin C is present in a variety of store-bought juices. The indicator solution will turn from dark blue to colorless once all the indophenol has reacted with vitamin C in the juices. Students will count how many drops of juice it takes to produce this color change in a 5-mL sample of indicator solution. The greater number of drops it takes to cause the color change, the less vitamin C is present in each drop. They will use their data to compare the relative amounts of vitamin C in the juices to a solution prepared from a vitamin C tablet.

Grade Level

Middle School, High School

NGSS Alignment

This lesson will help prepare your students to meet the following scientific and engineering practices:

  • Scientific and Engineering Practices:
    • Using Mathematics and Computational Thinking
    • Analyzing and Interpreting Data
    • Engaging in Argument from Evidence
    • Obtaining, Evaluating, and Communicating Information


By the end of this lesson, students should be able to:

  • Use a simplified titration procedure to determine if vitamin C is present in different commercially available juices and compare relative amounts.
  • Understand the basic principles of titration.

Chemistry Topics

This lesson supports students’ understanding of:

  • Concentration
  • Chemical reactions
  • Indicators
  • Titration


Teacher Preparation: 30 minutes
Lesson: 45 minutes


  • 2,6 dichloroindophenol sodium salt, 0.025% w/v solution in water (see teacher notes for prep)
  • Graduated cylinders (10 mL) or disposable pipette (5 mL) to dispense indicator solution
  • Clear plastic cups (8-ounces)
    • 1 cup per student lab station plus 1 cup for vitamin C solution and each juice sample
  • Disposable plastic pipettes for vitamin C solution and juice samples, 1 for each sample
  • Vitamin C tablet (500 mg), ground and dissolved in 10-mL distilled water
  • Orange juice (prepared from pulp-free frozen concentrate, e.g. Minute Maid)
  • Selection of juices – for example: Capri Sun, Arizona green tea, apple juice, pineapple juice, lemonade, Gatorade, Sunny D, Vitamin Water, etc.
  • Plastic rinse bottles with water, 1 per student lab station
  • “Dump” buckets (~500 mL plastic container), 1 per student lab station
  • Plastic trays or paper plates for reagent and lab stations (to control spills)
  • Student handouts


  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them on how to clean up their materials and properly dispose of chemicals.
  • Do not consume lab solutions, even if they’re otherwise edible products.

Teacher Notes

  • This lab is appropriate for middle school students or general level high school students. Prior to completing this lab, students should have a basic understanding of concentration (though they do not need to know specific units like molarity). They will be introduced to the fundamentals of titration and indicators in an approachable way that is appropriate for younger and less experienced students, as they will compare relative amounts of vitamin C in various juices rather than having them calculate how much vitamin C is present by mass. (See the extensions listed at the end of the teacher notes for ways to introduce a more quantitative analysis.)
  • The background reading may be a bit advanced for middle school students or less confident readers – this could be a good opportunity to help them develop their confidence and reading skills! There are “check in” questions after each paragraph to help break up the reading and give students a chance to make sure they have processed and understood what they have read, but it might also be useful to read through that information and answer the questions as a whole class. The teacher or student volunteers could model active reading techniques, such as circling unfamiliar words and looking them up, underlining important ideas, writing questions in the margins, etc. The Chemistry Close Read activity in the AACT resource library and the related Chemistry Solutions article provide good guidance on modeling and encouraging active reading.
  • Lab groups should include 2-4 students, depending on class size.
  • Preparation of 0.025% (w/v) Indophenol Solution: Weigh 125 mg (0.125 g) of the 2,6-dichloroindophenol sodium salt (can be purchased from such sites as Flinn Scientific and Home Science Tools) and dissolve in distilled water to a final volume of 500 mL. This will be enough for 10 lab groups to test 8 or 9 different juice samples with a 5-mL sample of indicator solution (80 or 90 tests total), with a little left over to account for pre-lab testing by the teacher, spills, etc. Amounts can be scaled up or down to accommodate the number of 5-mL samples and lab groups anticipated for the activity.
    • Be sure to prepare enough solution for all lab groups in a single batch (if possible) so that the concentration of the indicator solution is uniform to allow for a valid comparison of data between groups.
    • Indophenol solution is not very shelf stable, so prepare it as close to the lab day as possible (preferably on lab day) and store refrigerated in a dark or foil-covered bottle.
    • It is recommended that the instructor test out several juice samples on their own to make sure the indicator concentration works for the variety of juices being tested. An “ideal” standard would be 5 drops of orange juice (prepared from frozen concentrate) turning 5 mL indicator solution from blue to colorless. You can adjust the concentration slightly higher or lower if needed. Testing other juices will give the instructor a preview of what to expect from students’ determinations.
    • Place indophenol solution in a capped bottle on a plastic tray to contain spills. It is recommended that the indophenol solution is staged away from the juice samples. Pour about 100 mL into a beaker with a dedicated 10-mL graduated cylinder or a 5-mL plastic disposable pipette for students to measure out their samples. Refill beaker as needed. Since each test requires a new indophenol sample, several beakers of indophenol can be placed around the room so that all students aren’t waiting in line for just one beaker.
    • For indophenol spills or stains, simply treat with vitamin C solution. The blue stain will disappear.
  • Prepare the vitamin C solution by crushing one 500 mg vitamin C tablet and mixing with 10 mL distilled water. (Vitamin C tablets should be available in most grocery stores or drug stores, such as Walgreens, CVS, etc.) The vitamin is soluble in water, but some tablet bulking agents may not be. In this case, simply let solid materials settle and decant solution to a clean sample cup. This volume is enough for at least two full classes, and the solution must be made fresh each day. The pure vitamin C sample should be the last sample tested by each group.
  • Set each juice sample on a tray to control spills. Pour approximately ¼ cup of each juice into a labeled 8-ounce cup and set on a long table, counter, or on any stable flat surface around the classroom. To control foot traffic, have lab groups send one student to retrieve one juice sample at a time to test at their lab station. Each juice sample must have a dedicated plastic pipette.
  • A brief tutorial on the proper use of a graduated cylinder is recommended. This AACT simulation could help students practice with significant figures and uncertainty when reading graduated cylinders.
  • You may want to give students some pointers on proper pipette technique:
    • Remind them to hold the pipette perpendicular to the lab table (or at least holding it the same way every time they add a drop) to make sure drop size is as consistent as possible.
    • Encourage them to pay close attention to which dropper goes with which juice to avoid cross-contamination, and remind them not to touch the dropper to any other solutions.
    • Inconsistencies in dropper technique may be cited as a source of variation or error in data analysis.
  • The data table and graph in the student document can be customized to fit the number of juice samples you would like students to test.
  • Depending on the grade level, time allotted for the activity, availability of supplies, etc. the number of juice samples tested can be limited. For example, perhaps 10 different juice options are offered but each group only picks 5 to test.
    • To promote student ownership of the learning activity, students could be given the option to bring in a juice of their own to test.
  • Following the lab activity, allow students to compare results with other groups, discuss patterns and potential sources of variation in data within and between lab groups.
  • Extension opportunities:
    • Compare the vitamin C content of bottled or processed juice to that of freshly squeezed juice (ex: store bought bottle of orange juice vs. orange juice from concentrate vs. freshly squeezed oranges, or bottled lemon juice vs. lemonade vs. freshly squeezed lemons)
    • Provide samples of juice that have been subjected to a variety of lighting and temperature conditions to study the effect of light and heat exposure on vitamin C content of a favorite bottled juice. A student can make connections between recommended storage in a refrigerator, packaging, and expiration dates. This study is appropriate for a Science Fair presentation.
    • For more advanced students, particularly at the high school level, reagent grade vitamin C (L-ascorbic acid) could be used in place of the drugstore tablet to make a vitamin C solution with high levels of precision (ex: 0.100 g per 100 mL). A solution whose concentration is known very precisely would serve as a standard that students could use to determine quantitatively the mass of vitamin C per a given volume of juice. See Flinn Scientific’s “Vitamin C Testing” resource for sample calculations, chemical equations, molecular structures, etc..

For the Student


Vitamin C, also called ascorbic acid, is important for your health. However, our bodies don’t make it, so we have to get it from what we eat and drink. One good source of vitamin C is citrus fruit, such as oranges, lemons, and limes, and their juices. Some people make sure they get enough vitamin C by taking daily vitamins or supplements. It is also often added to juices to make them more nutritious.

Check-in: What is another name for vitamin C?

In this lab, you will be using a method called titration to see if a variety of juices from the grocery store have vitamin C in them and how they compare to a vitamin supplement. Titration is a process chemists use to find out how much of a specific substance (in this case, vitamin C) is present in a sample (the juice samples) by observing how much of it reacts with a certain amount of another substance.

Check-in: What are you trying to learn about the juice samples you will be testing?

In this simplified titration, you will observe the reaction between vitamin C and an indicator solution called indophenol. It is called an indicator because it shows scientists when the reaction is complete based on a color change that occurs when all the indophenol has reacted. This color change is called the endpoint of the reaction. You will slowly add drops of juice to a 5-mL sample of indophenol. Once enough vitamin C has been added to react with all the indophenol, the solution will change from deep blue to colorless. Watch carefully as this may happen with a single drop of juice!

Check-in: How will you know when all the indophenol has reacted with vitamin C?

If your juice has a lot of vitamin C, you won’t need to add very many drops to reach the endpoint. Likewise, if your juice has only a little vitamin C, you will need many more drops to reach the endpoint. Using this method, you will compare how much vitamin C is in a variety of juices, as well as a dissolved vitamin C tablet.

Check-in: How will you know which juice has the most vitamin C?

Prelab Questions

Use the article below to answer the following questions about vitamin C. https://medlineplus.gov/ency/article/002404.htm

  1. List two things vitamin C does to keep your body healthy.
  2. Vitamin C is an “antioxidant.” What do antioxidants do for health?
  3. List three foods that are good sources of vitamin C.
  4. What are three possible side effects of not getting enough vitamin C?
  5. What is your recommended dietary allowance (RDA) of vitamin C?


Identify which juice samples contain vitamin C and put them in order from most vitamin C to least vitamin C.


  • Clear plastic cup
  • Rinse bottle with water
  • Large (~500 mL) plastic “dump” bucket
  • Indophenol indicator solution (prepared by the instructor)
  • Juice samples (prepared by the instructor) with pipettes
  • Vitamin C solution (prepared by the instructor)
  • Optional: Plastic tray or large paper plate to control spills


  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • When you complete the lab, follow the teacher’s instructions for cleaning up materials and properly disposing chemicals.
  • Do not consume lab solutions, even if they’re otherwise edible products.


  1. One group member should measure 5 mL of indicator solution using a graduated cylinder and pour this into your group’s plastic cup. Bring your measured indicator solution back to your lab station.
  2. Another group member should select a juice to be tested and take the cup of juice and its pipette to your lab station. The juice selections will be in cups on trays with dedicated plastic pipettes for each type of juice.
  3. Write the name of the juice being tested in your data table.
  4. Use the pipette to add juice drop by drop to the indicator solution in your cup, swirling gently after each drop to make sure it reacts completely. Count the number of drops it takes to change the indicator solution in your cup from blue to colorless and record that number in your data table.
  5. If a juice does not turn the indicator colorless after 30 drops, stop adding juice and record it as “30” drops in your data table.
  6. Pour the contents of your cup into the “dump” bucket and rinse well with water for the next sample. Return the juice sample before selecting another one.
  7. Repeat steps 1-6 with different juice samples until you have filled your data table (except for the last column, labeled “Vitamin C”).
  8. After you have tested your juice samples, repeat steps 1-6 with the vitamin C solution prepared by your teacher.


In “Table 1” below, record how many drops of juice were needed to reach the endpoint. Then create a bar graph of your data in “Graph 1” below.

Table 1: Vitamin C Drop Test Data

Type of Juice Sample 1: Sample 2: Sample 3: Sample 4: Sample 5:
Number of Drops
Type of Juice Sample 6: Sample 7: Sample 8: Sample 9: Vitamin C
Number of Drops

Graph 1: Drops of Juice Added to Produce Color Change


  1. Based on your data, rank your juices from highest to lowest based on vitamin C content. Justify your answer.
  2. Using data from this activity, how does the juice with the highest vitamin C content compare to a vitamin C tablet?
  3. Were there any juices that had no (or very little) vitamin C? If so, which ones? Did you expect these results?
  4. Did any of the juices you sampled today give a surprising or unexpected result? Explain.
  5. How do your results compare with other teams in class? Provide one possible reason for the differences in your results for the same juice sample.