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Testing Vitamin C

  1. Overview
  2. Introduction
  3. Materials
  4. Instructions
  5. Activity Questions
  6. Assessment
  7. Suggestions for Expanding the Activity
  8. Learning Standards

Overview

During this hands-on activity, students will test different juices for their vitamin C content. This activity demonstrates how to perform a titration. This activity is simple and inexpensive, yet it provides endless possibilities for lesson expansion and fullfillment of learning standards. You can incorporate a lesson on pH, acids, and bases into this lesson.

Introduction

Related Concepts

The concept that will be focused on for this lesson is performing a titration. In this activity, participants will determine how much Vitamin C is in a variety of juices and beverages.

Background Information

Participants are going to be performing a titration, a simple procedure for finding the concentrations or amounts of substances in solutions. In this test we will be using Vitamin C.

Before the activity can begin, starch solution must be added to the beverages that are to be tested. Iodine will then be added dropwise to each of the beverages. As iodine is added, it will first react with the ascorbic acid in the beverage, producing a colorless product (dehydroascorbic acid). When the ascorbic acid runs out, the iodine will react with the starch in the beverage. At this point, participants will be able to recognize a highly visible color change. This color change is the endpoint of the reaction. Therefore, the more iodine added, the more Vitamin C the beverage contained.

Getting the Lesson Started!

Here are some potential discussion questions

  1. What vitamin is found in orange and lemon juice?
  2. What other beverages do you think contain Vitamin C?
  3. Of those you listed, which do you think contain the most?
  4. Do you think there is a way that we can determine the amount of Vitamin C in each of the beverages?

Materials

  • various juice drinks (we used orange juice, lemon juice, lemonade, orange HI-C, apple juice, and fruit flavored carbonated beverages, such as Sprite)
  • a pipette for each beverage
  • a plastic cup for each beverage
  • iodine solution
  • starch solution (consisting of 1 part baking soda to 5 parts water)
  • toothpicks or stirring rods

Instructions

  1. Pour about 1 ounce of each beverage into a separate plastic or paper cup.
  2. With a pipette, add about 10 drops of the starch solution to each cup. Stir each solution with a toothpick or stirring rod.
  3. Begin adding the iodine to one of the solutions a drop at a time. Make sure you count the number of drops you are adding. Stir the solution after the addition of each drop.
  4. As drops are continually added, the solution will change color. When the solution first changes color, stir for at least 20 seconds. If the original color reappears, more iodine must be added. If the color change persists, you have reached the endpoint. (The right picture below shows an example of a beverage after it has reached the endpoint.)
  5. Record the number of drops needed to reach the endpoint.
  6. Repeat the above procedure for each of the solutions you are testing.

Activity Questions

Observations

Data Chart for Titrations

Directions: For each beverage, write the amount of drops used to change the color of the solution. Then rank the beverages in order from most Vitamin C to least.

Beverage Number of Drops Rank
Orange Juice    
Lemon Juice    
Lemonade    
Apple Juice    
Orange HI-C    
Other    
Other    
Titration Graph

For each beverage, color in the amount of drops used to turn the beverage to a different color. If more than twenty drops are used, fill in the entire column and write the number of drops at the top of the column.

Number of Drops 20              
19              
18              
17              
16              
15              
14              
13              
12              
11              
10              
9              
8              
7              
6              
5              
4              
3              
2              
1              
  Orange Juice Lemon Juice Lemonade Apple Juice Orange Hi-C Other Other
Beverage

Questions

  1. Which beverage had the least amount of Vitamin C in it? How do you know?
  2. Which beverage had the greatest amount of Vitamin C in it? How do you know?
  3. Were you surprised by any of the results? Explain.

Assessment

Assessment Background

Our assessment methods were the same for Illinois and National Standards.

Our assessment methods were the same and for Early and Late Elementary School students. What changed was the level of the questions asked and the discussion.

During the Lesson

The participants used inquiry strategies to successfully determine how to perform a titration. Throughout the lesson, the participants discussed the inter-relationships between science, technology, and society by discussing the importance of Vitamin C in our diet.

At the End of the Lesson

At the conclusion of the lesson, a discussion was held to determine the level of participant understanding of how and why a titration is performed. The discussion also encouraged students to think critically about the role of Vitamin C to our health.

Here is a sample of questions from that discussion:

  • How is a titration performed?
  • What does a titration tell us?
  • Could a titration be done to determine other things besides Vitamin C content?
  • Which tested beverages were high in Vitamin C?
  • Were you surprosed by any of the results? Explain.

Each of the children who participated in the lesson was able to answer these questions at his/her own level.

Suggestions for Expanding the Activity

Testing the pH.

This lesson can be greatly expanded by adding the concepts of pH and acids and bases. While performing this lesson, it would be appropriate to measure the pH of each of the beverages as well. The pH can easily be determined with a pH indicator strip. Once the pH has been determined, students can decide if the beverage is a acid or a base. Since all of the beverages in the Vitamin C test are acids, you may want to add solutions that are bases such as Laundry detergent, antacid solution, cleaning products, etc.

Here is a sample chart for this information:

Directions: For each sample, write the pH. The write whether the sample was an acid or a base.

Illinois State and National Learning Standards that Apply to this Lesson

The following standards are from the Illinois Learning Standards, adopted by the Illinois State Board of Education on July 25, 1997. Take a look at the complete Illinois Learning Standards for Science, and for English/Language Arts.

Early Elementary

Subject Goal Standard Application to
this Lesson
Science State Goal 11: Understand the processes of scientific inquiry and technological design to investigate questions, conduct experiments, and solve problems. A. Know and apply the concepts, principles and processes of scientific inquiry.
  • 1a. Desribe an observed event.
  • 1c. Collect data for investigations using measuring instruments and technologies.
  • 1d. Record and store data using available technologies.
  • 1f. Compare observations of individual and group results.
Participants will collect and record data while they are performing the titrations. They will be asked to describe what they observed and decide which beverages contain the most Vitamin C. At the end of the lesson, participants will comapre their results with the results of the other participants.
Science State Goal 12: Understand the fundamental concepts, principles, and interconnections of the life, physical, and earth/space sciences. A. Know and apply concepts that explain how living things function, adapt, or change.
  • 1a. Identify and describe the component parts of living things and their major functions
Participants will discuss the inportance of Vitamin C to the human body. This will help to illustrate the importance of determining which beverages contain the most Vitamin C.
Science State Goal 13: Understand the relationships among science, technology, and society in historical and contemporary contexts. A. Know and apply the accepted practices of science.
  • 1a. Use basic safety practices (e.g., not tasting materials without permission).
  • 1b. Explain why similiar results are expected when procedures are done the same way.


B. Know and apply concepts that describe the interaction between science, technology, and society.
  • 1b. Explain how using measuring tools improves the accuracy of estimates.
Participants will be expected to use safety procedures while performing this and all other activities. Participants will discuss how using measuring tools will result in more accurate results.
English/Language Arts State Goal 1: Read with understanding and fluency. C. Comprehend a broad range of reading materials.
  • 1a. Use information to form questions and verify predictions.
Participants will use the information they gathered about titrations to formulate questions about how they could test other substances for vitamin content.
English/Language Arts State Goal 3: Write to communicate to a variety of purposes. C. Communicate ideas in writing to accomplish a variety of purposes.
  • 1a. Write for a variety of purposes including description, information, explanation, persuasion, and narration.
Participants will answer various questions about their experience and about titrations. They will also be asked to write about the importance of Vitamin C.
English/Language Arts State Goal 4: Listen and speak effectively in a variety of situations. A. Listen effectively in formal and informal situations.
  • 1b. Ask questions and respond to questions from the teacher and from group members to improve comprehension.
  • 1c. Follow oral instructions accurately.
B. Speak effectively using language appropriate to the situation and audience.
  • 1a. Present brief oral reports, using language and vocabulary appropriate to the message and audience (e.g., show and tell).
  • 1b. Participate in discussions around a common topic.
At the beginning of the lesson, participants are given oral and written instructions to assist them with the activity. Their succes is based on how effectively they follow the given instructions. At the end of the lesson, participants are involved in a discussion that requires them to listen effectively to a question and answer session. Participation is encouraged from every student during the discussion at the end of the lesson.

Late Elementary

Subject Goal Standard Application to this Lesson
Science State Goal 11: Understand the processes of scientific inquiry and technological design to investigate questions, conduct experiments, and solve problems. A. Know and apply the concepts, principles and processes of scientific inquiry.
  • 2b. Collect data for investigations using scientific process skills including observing, estimating and measuring.
  • 2d. Use data to produce reasonable explanations.
Participants will collect and record data while they are performing the titrations. They will be asked to describe what they observed and decide which beverages contain the most Vitamin C. At the end of the lesson, participants will comapre their results with the results of the other participants.
Science State Goal 13: Understand the relationships among science, technology, and society in historical and contemporary contexts. A. Know and apply the accepted practices of science.
  • 2a. Demonstrate ways to avoid injury when conducting science activities.
  • 2c. Explain why keeping accurate and detailed records is important.


B. Know and apply concepts that describe the interaction between science, technology, and society.
  • 2a. Explain how technology is used for a variety of purposes (e.g., measurement, data collection, etc.)
Participants will be expected to use safety procedures while performing this and all other activities. Participants will discuss how using measuring tools will result in more accurate results.
English/Language Arts State Goal 1: Read with understanding and fluency. C. Comprehend a broad range of reading materials.
  • 2d. Summarize and make generalizations from content and relate to purpose of material.
Participants will use the information they gathered about titrations to formulate questions about how they could test other substances for vitamin content.
English/Language Arts State Goal 3: Write to communicate to a variety of purposes. C. Communicate ideas in writing to accomplish a variety of purposes.
  • 2a. Write for a variety of purposes and for specified audiences in a variety of forms.
Participants will answer various questions about their experience and about titrations. They will also be asked to write about the importance of Vitamin C.
English/Language Arts State Goal 4: Listen and speak effectively in a variety of situations. A. Listen effectively in formal and informal situations.
  • 2c. Restate and carry out a variety of oral instructions.
B. Speak effectively using language appropriate to the situation and audience.
  • 2b. Use speaking skills and procedures to participate in group discussions.
At the beginning of the lesson, participants are given oral and written instructions to assist them with the activity. Their succes is based on how effectively they follow the given instructions. At the end of the lesson, participants are involved in a discussion that requires them to listen effectively to the questions. Participation is encouraged from every student during the discussion at the end of the lesson.

National Learning Standards that Apply to this Lesson

Standard Level Application to this Lesson
6.1 Science as Inquiry K-4, 5-8, 9-12
Abilities to do scientific inquiry

K-4, 5-8, 9-12
Understanding about scientific inquiry
Participants will use scientific reasoning and critical thinking while testing the various beverages for Vitamin C content. Participants will ask questions, conduct investigations, and gather information to help them understand how to perform titrations and the importance of vitamins.
6.2 Physical Science K-4
Properties of objects and materials

5-8
Properties and changes of properties in matter

9-12
Chemical reactions
Participants are introduced to titrations and their importance. Once participants have performed the titrations, they can analyze their data and classify each beverage. Participants in grades 9-12 can discuss the chemical reaction that is taking place in this particular titration.
6.6 Science in Personal and Social Perspectives K-4, 5-8
Personal Health

9-12
Personal and Community Health
Participants were involved in a discussion that explained the importance of Vitamin C. Participants then developed reasons for wanting to determine the Vitamin C content of popular beverages.