• OverviewOverview
  • ObjectiveObjective
  • GradeGrade
  • TimeTime
  • PreparationPreparation
  • NotesNotes
  • ProcedureProcedure
  • WorksheetWorksheet
  • AssessmentAssessment
Overview
Overview

      Why did sailors lacking fruits and vegetables die of a strange disease during the voyage? Through a fun magic trick, the teacher will show students how to detect vitamin C. Students will personally verify whether vitamin C is contained in frequently eaten fruits and vegetables, and compare the vitamin C content of various fruits and vegetables based on the speed of color change. 

     Is it okay to eat only vegetables with the highest vitamin C content? Through experiments, students will learn about the effect of cooking on the vitamin C content of vegetables, discuss the dietary structure and food cooking methods, and build a healthy dietary pattern. 

Keywords: vegetable juice; vitamin C; nutrition

      Why did sailors lacking fruits and vegetables die of a strange disease during the voyage? Through a fun magic trick, the teacher will show students how to detect vitamin C. Students will personally verify whether vitamin C is contained in frequently eaten fruits and vegetables, and compare the vitamin C content of various fruits and vegetables based on the speed of color change. 

     Is it okay to eat only vegetables with the highest vitamin C content? Through experiments, students will learn about the effect of cooking on the vitamin C content of vegetables, discuss the dietary structure and food cooking methods, and build a healthy dietary pattern. 

Keywords: vegetable juice; vitamin C; nutrition

Objective
Objective

(1)Scientific knowledge

  • Know the name of some common vitamins, how they are classified and that vitamin C is a water-soluble vitamin; 
  • Know that the starch-iodine solution is blue and how to prepare it; 
  • Capable of analyzing problems dialectically under the guidance of the teacher and become aware of the scientific dietary pattern; 

(2)Scientific exploration

  • Through fun magic tricks and stories about scientists' scientific discoveries, students will have a cognitive conflict, which will in turn stimulate students' curiosity and desire to explore and the enthusiasm for practice; 
  • Students can design experiments based on their existing experience and knowledge, thereby cultivating their ability to design experiments; 
  • Students can compare and analyze different experimental observations; 
  • Through experimental demonstration, students are guided to design a relatively comprehensive inquiry plan, and will learn to reflect and make corrections; 
  • Students' ability to conduct hands-on experiments can be enhanced. 

(3)Scientific attitude

  • Eager to dig into the interesting and unknown phenomena presented by the teacher and try out actively; 
  • Learn the ways to divide work during multi-person cooperation, cultivate the teamwork spirit, and feel the joy of experimentation, thereby contributing to the sustainable development of practical inquiry in the future science study of students; 
  • Respect the experimental results, capable of reflecting on and adjusting the experimental steps of the group after obtaining results inconsistent with other groups, and draw the collective conclusion of the group through proactive communication and comprehensive consideration. 

(4)Science, technology, society and environment

  • Students can name familiar vitamins, choose their own foods reasonably, and build a healthy dietary pattern; 
  • Recognize the important role of the reasonable intake of fruits and vegetables to our health; 
  • Recognize the interdependent relationship between plants and humans. 

(1)Scientific knowledge

  • Know the name of some common vitamins, how they are classified and that vitamin C is a water-soluble vitamin; 
  • Know that the starch-iodine solution is blue and how to prepare it; 
  • Capable of analyzing problems dialectically under the guidance of the teacher and become aware of the scientific dietary pattern; 

(2)Scientific exploration

  • Through fun magic tricks and stories about scientists' scientific discoveries, students will have a cognitive conflict, which will in turn stimulate students' curiosity and desire to explore and the enthusiasm for practice; 
  • Students can design experiments based on their existing experience and knowledge, thereby cultivating their ability to design experiments; 
  • Students can compare and analyze different experimental observations; 
  • Through experimental demonstration, students are guided to design a relatively comprehensive inquiry plan, and will learn to reflect and make corrections; 
  • Students' ability to conduct hands-on experiments can be enhanced. 

(3)Scientific attitude

  • Eager to dig into the interesting and unknown phenomena presented by the teacher and try out actively; 
  • Learn the ways to divide work during multi-person cooperation, cultivate the teamwork spirit, and feel the joy of experimentation, thereby contributing to the sustainable development of practical inquiry in the future science study of students; 
  • Respect the experimental results, capable of reflecting on and adjusting the experimental steps of the group after obtaining results inconsistent with other groups, and draw the collective conclusion of the group through proactive communication and comprehensive consideration. 

(4)Science, technology, society and environment

  • Students can name familiar vitamins, choose their own foods reasonably, and build a healthy dietary pattern; 
  • Recognize the important role of the reasonable intake of fruits and vegetables to our health; 
  • Recognize the interdependent relationship between plants and humans. 

Grade
Grade

Grades 4-6, no more than 30 students at a time. 

Grades 4-6, no more than 30 students at a time. 

Time
Time

About 90 minutes.   

About 90 minutes.   

Preparation
Preparation

Venue: laboratory (or a classroom near the pool); desks, chairs and multimedia equipment. 

Preparations:   

A. Worksheet; 

B. Activity materials (to be prepared as per the quota for 5 persons per group, or the quantities used in the last class)

SN

Item

Quantity

SN

Item

Quantity

1

Beaker

50

10

Starch

1 bag

2

Dropper

50

11

Iodine tincture

1 bottle

3

Mortar

10

12

Label

1 bag

4

Glass rod

5

13

Tomato

Some

5

Gauze

5

14

Cucumber

Some

6

Alcohol burner

5

15

Green pepper

Some

7

Stopwatch

5

16

Pear

Some

8

Asbestos net

5

17

Apple

Some

9

Measuring cylinder

5

 

 

 

Venue: laboratory (or a classroom near the pool); desks, chairs and multimedia equipment. 

Preparations:   

A. Worksheet; 

B. Activity materials (to be prepared as per the quota for 5 persons per group, or the quantities used in the last class)

SN

Item

Quantity

SN

Item

Quantity

1

Beaker

50

10

Starch

1 bag

2

Dropper

50

11

Iodine tincture

1 bottle

3

Mortar

10

12

Label

1 bag

4

Glass rod

5

13

Tomato

Some

5

Gauze

5

14

Cucumber

Some

6

Alcohol burner

5

15

Green pepper

Some

7

Stopwatch

5

16

Pear

Some

8

Asbestos net

5

17

Apple

Some

9

Measuring cylinder

5

 

 

 

Notes
Notes

      ①The teacher can design the pre-activity plan, notice to parents and other documents according to the actual needs. 

      ②Students must abide by the code of civilized conduct. Without the instruction of the teacher, the students should not touch the experimental reagents and instruments on the experimental table at will, and should not make any loud noises. In the classroom, students need to abide by the laboratory's rules of conduct, take good care of public property, and follow the laboratory discipline. During the experiment, when the students need to use alcohol burner and laboratory equipment made of glass, the teacher should keep reminding students to pay attention to their safety and to prevent the glass equipment from breaking and hurting themselves or others. 

      ③The teacher needs to give psychological counseling for students who have failed the experiment. 

      ①The teacher can design the pre-activity plan, notice to parents and other documents according to the actual needs. 

      ②Students must abide by the code of civilized conduct. Without the instruction of the teacher, the students should not touch the experimental reagents and instruments on the experimental table at will, and should not make any loud noises. In the classroom, students need to abide by the laboratory's rules of conduct, take good care of public property, and follow the laboratory discipline. During the experiment, when the students need to use alcohol burner and laboratory equipment made of glass, the teacher should keep reminding students to pay attention to their safety and to prevent the glass equipment from breaking and hurting themselves or others. 

      ③The teacher needs to give psychological counseling for students who have failed the experiment. 

Procedure
Procedure

Before activity

Teacher

Students

The teacher will make the "blue ink" to be used in the small magic tricks—starch-iodine solution—and stick a vitamin C tablet inside the bottle cap before the activity. 

As requested by the teacher, students will sit in groups in the activity classroom. 

Stage 1: Lead-in—The teacher will use a magic trick and a short story to stimulate students' interest and to introduce the knowledge point. Through a historical story, students will understand the importance of vitamin C to the human body and what foods are rich in vitamin C.  

Suggested duration: 10 minutes  

Teacher

Students

  1. A fun magic trick

        The starch-iodine solution looks like the blue ink placed in a transparent bottle. After shaking the bottle, the solution will immediately fade its blue ink-like color. 

      (Uncover the secret: a Vitamin C tablet is stuck inside the bottle cap.)

Question: What do you know about vitamin C tablet? 

  1. Tell a short story about the discovery of Vitamin C: 

         Outline: 

    During Columbus's voyage when the America was discovered, many crew members became sick, suffering from fatigue and gum-bleeding, and even died. 

     Dr. James Lind believed that fresh fruits and vegetables might be the cure. Later, they ran into a Dutch cargo ship full of oranges and lemons. Dr. Lind bought oranges and lemons to treat patients with scurvy and found that the curative effect was good. 

Student's answer: Vitamin C is contained in fruits and vegetables, in some beverages, and in the Vitamin C effervescent tablets. 

 

Students will learn from the story that vitamin C is contained in fruits and vegetables, and the importance of vitamin C to the human body.   

 

Activity Design: 

      The teacher will use a small trick to quickly draw the attention of students, and then introduce the substance of vitamin C. Based on their daily life experience, students in the upper grades of elementary school know that vitamin C is contained in fruits and vegetables. The demonstration of small trick also secretly shows a method to detect vitamin C. According to the foods containing vitamin C named by students, the teacher will smoothly proceed to the second stage of this activity—to explore whether the fruit juices contain vitamin C. 

      The fun magic trick and the short story can stimulate students' curiosity, arouse students' enthusiasm for participation, strengthen their desire to explore, promote their thinking, and reinforce their impression of the knowledge. 

Stage 2: Inquiry  

1. Learn to prepare starch-iodine solution. Through a series of small experiments to mix vegetable and fruit juices with the starch-iodine solution, students will intuitively and clearly understand the presence of vitamin C in vegetable juice. 

2. The pre-class magic trick will help students gain the initial knowledge and prepare the ground for students to successfully design related experiments. Next, the teacher will distribute worksheets to present a complete experiment procedure and to guide the students to design the specific steps of the experiment by themselves—one of the objectives of the scientific inquiry for students in the upper grades of elementary school. By filling out the worksheet, students will also cultivate a scientific attitude toward experiments. When the experimental results are different from those of other groups, students can discuss with each other in order to improve their ability to analyze problems. 

Suggested duration: 30 minutes

Teacher

Students

  1. The teacher will explain the scientific principle behind the pre-class magic trick and ask students to learn how to prepare the starch-iodine solution. 
  2. The teacher will guide students to learn that vitamin C is contained in fruits and vegetables and is important to the human body, and ask students to design their own experiments to verify the existence of vitamin C in fruits and vegetables. 

According to the teacher's demonstration, students will learn to prepare the starch-iodine solution, and verify the existence of vitamin C in fruits and vegetables through experiments designed under the guidance of the teacher. 

Activity Design: 

       Students seldom have the opportunity to conduct hands-on experiments in the school. The materials used in this experiment are some commonly seen fruits and vegetables, as well as starch and iodine tincture, which are all things familiar to them. Through the experiment, students can intuitively learn the existence of vitamin C in fruits and vegetables, and realize the importance of vitamin C to the human body through the short historical story, thereby attending to the intake of fruits and vegetables in their diet. 

      Students mainly obtain knowledge indirectly through textbooks and dictation by elders. By splitting into groups and undertaking inquiry on their own to draw experimental conclusions, students can improve their hands-on skills and cultivate the teamwork spirit. 

      Guiding students to design the specific steps of the experiment by themselves is also one of the objectives of the scientific inquiry for students in the upper grades of elementary school. The pre-class knowledge taught by the teacher will prepare the ground for students to successfully design related experiments. The teacher will subsequently distribute worksheets to help students improve the experiment design. By filling out the worksheet, students will also cultivate a scientific attitude toward experiments. When the experimental results are different from those of other groups, students can discuss with each other in order to improve their ability to analyze problems.   

Stage 3: Explanation—Through the "Starch-Iodine Solution Color Fading Experiment" and the "Experiment of Fading Starch-Iodine Solution with Vegetables and Fruits", students will discuss the scientific principle behind the experimental phenomena.   

Suggested duration: 15 minutes  

Teacher

Students

  1. Share experimental results with the whole class. 

Experiment 1: 

       (1)Measure 50ml of water with a measuring cylinder and pour it into a conical flask, and the clear water will become a white turbid solution. This is because small water-insoluble starch particles are dispersed in water. 

      (2)Add 6 drops of iodine tincture to the starch solution, and the solution will turn blue. This is because the starch will turn blue when mixed with iodine. 

       Scientific principle behind the fun magic trick

       Vitamin C can react with the iodine in the blue solution, so the starch-iodine compound in the solution will be destructed and the blue color will fade. 

Experiment 2: 

       All fruits and vegetables given can fade the blue color of starch-iodine solution, so students can conclude that these fruits and vegetables all contain vitamin C. 

       The fading speed can indicate the concentration of vitamin C in the vegetable and fruit juices. 

  1. Discussion

       Green pepper is rich in vitamin C, so Xiaoming only eats green peppers. Is this the right way? 

      Conclusion: The diet should be diverse, because there are diverse nutrients. The choice of foods should be aligned to individual needs (due to individual differences, some people may suffer allergy or diarrhea after eating certain foods). 

Since experimental classes are relatively limited in the school, the teacher will hand out the worksheets, under the guidance of which students will be able to complete the experiments step by step, fill in their experimental observations, and think carefully. 

Students will come to the following conclusion: According to individual differences, the diet should highlight diversity and the combination of different foods. 

 

Activity Design: 

      Students will conduct experiments in groups to cultivate teamwork spirit, improve practical skills, learn the simple analysis of phenomena, and cultivate the rigorous scientific spirit. Finally, the students will discuss the wrong dietary patterns to enhance the practicality of this activity. The teacher will explain the scientific principle behind the experimental phenomena and base the summary on the students' existing knowledge and experiences. 

Stage 4: Knowledge transfer. Vitamins will almost disappear after the food is cooked for a long time, so the cooking time should be as short as possible. The teacher will use the original fruit/vegetable juice and the cooked fruit/vegetable juice to conduct the comparative experiment of fading the starch-iodine solution, thereby summing up the relationship between the heating time and the vitamin C concentration in the fruit/vegetable juice. 

    Through the previous two experiments, students have learned the method of detecting vitamin C, and will continue to design new experiments independently under the guidance of the teacher in order to find out whether vegetables should be eaten raw or cooked. After summing up students' ideas, the teacher will hand out worksheets to present a complete experiment procedure and to guide the students to design the specific steps of the experiment and a comprehensive inquiry plan by themselves—one of the objectives of the scientific inquiry for students in the upper grades of elementary school, and also the necessary moves to cultivate students' scientific attitude toward experiments. 

Suggested duration: 25 minutes

Teacher

Students

  1. Generally, vegetables are eaten only after they are cooked, while fruits are eaten directly. So, will vegetables be more nutritious after being cooked? 

     To understand whether vegetables should be eaten raw or cooked, students can design experiments to get the answer. The teacher can ask students to design experiments and draw their own conclusions. 

  1. Assign the task

      Think about it: Should vegetables be eaten raw or cooked? Students will carry out experiments in groups and fill out the worksheet carefully based on their experimental observations. (see the attached photos)

 

   Upon thorough discussion in groups, students will conduct experiments and fill out the worksheet based on the experimental results, thereby cultivating their scientific attitude toward experiments. When the experimental results are different from those of other groups, students can discuss with each other in order to improve their ability to analyze problems. 

     Although Grade 3 students must have used the alcohol burner before, it's still necessary for the teacher to remind students of their safety in using the alcohol burner. 

 

Activity Design: 

    Vitamins are essential nutrients for the human body. In spite of different dietary habits, vitamins will almost disappear after the vegetable juice is cooked for a long time. Through experiments, students can fully realize that vegetables must not be cooked for a long time. Food processing methods vary from people to people, and everyone can always find the best way they like to cook their foods. 

      The teacher must actively guide students to design the specific steps of the experiment and the inquiry plan by themselves. 

      In the final session of drawing conclusions, the teacher can guide the students to put forward their own views, analyze dialectically and think from different aspects. 

Stage 5: Knowledge summing-up. Students will know the classification of vitamins and the facts that the human body can only partially synthesize vitamins and that most vitamins must be obtained from foods. The teacher will also introduce several vitamins that students are familiar with. 

      Students can try to analyze and account for the doubts they may have based on the knowledge gained from the experiments. When drawing conclusions, the teacher must guide the students to put forward their own views, analyze dialectically and think from different aspects. 

Suggested duration: 10 minutes  

Teacher

Students

  1. Question

       Based on your own life experience, please conclude whether the vegetables should be eaten raw or cooked. Please give your reasons. 

      Under the guidance of the teacher, the students will analyze from multiple perspectives, such as nutrition, taste and individual differences. 

  1. Summary

      Vitamins can be divided into fat-soluble and water-soluble vitamins (for example, the sunscreen). 

      Fat-soluble vitamins can be dissolved and stored in fat, such as vitamin A (also known as anti-dry eye vitamin), vitamin D (synthesized by skin cells in the sun), vitamin E, etc. 

      Water-soluble vitamins are soluble in water, but cannot be stored in the body. They need to be taken from foods every day. Vitamin C and vitamin B are both water-soluble vitamins. 

       Whether vegetables should be eaten raw or cooked varies from person to person. For most people, the vegetables served on the dinner table should be cooked lightly, supplemented with some refreshing vegetable salads and finally with meat cooked with less oil. 

Although the senior-grade pupils must have gained certain life experience, their knowledge of vitamins is still very limited. Through the examples named by the teacher, students will understand the importance of vitamins and learn how to eat healthily. 

 

Activity Design: 

      According to the answers given by the students, the teacher will guide the students to think from multiple aspects and start with things they are familiar with, so as to evaluate how much the students have learned and to consolidate the knowledge they have gained. Students in the upper grades of elementary school must have certain generalization, explanation and analysis abilities. By asking questions, the teacher can test their mastery of relevant knowledge points, and guide them to analyze questions dialectically before drawing conclusions. 

Before activity

Teacher

Students

The teacher will make the "blue ink" to be used in the small magic tricks—starch-iodine solution—and stick a vitamin C tablet inside the bottle cap before the activity. 

As requested by the teacher, students will sit in groups in the activity classroom. 

Stage 1: Lead-in—The teacher will use a magic trick and a short story to stimulate students' interest and to introduce the knowledge point. Through a historical story, students will understand the importance of vitamin C to the human body and what foods are rich in vitamin C.  

Suggested duration: 10 minutes  

Teacher

Students

  1. A fun magic trick

        The starch-iodine solution looks like the blue ink placed in a transparent bottle. After shaking the bottle, the solution will immediately fade its blue ink-like color. 

      (Uncover the secret: a Vitamin C tablet is stuck inside the bottle cap.)

Question: What do you know about vitamin C tablet? 

  1. Tell a short story about the discovery of Vitamin C: 

         Outline: 

    During Columbus's voyage when the America was discovered, many crew members became sick, suffering from fatigue and gum-bleeding, and even died. 

     Dr. James Lind believed that fresh fruits and vegetables might be the cure. Later, they ran into a Dutch cargo ship full of oranges and lemons. Dr. Lind bought oranges and lemons to treat patients with scurvy and found that the curative effect was good. 

Student's answer: Vitamin C is contained in fruits and vegetables, in some beverages, and in the Vitamin C effervescent tablets. 

 

Students will learn from the story that vitamin C is contained in fruits and vegetables, and the importance of vitamin C to the human body.   

 

Activity Design: 

      The teacher will use a small trick to quickly draw the attention of students, and then introduce the substance of vitamin C. Based on their daily life experience, students in the upper grades of elementary school know that vitamin C is contained in fruits and vegetables. The demonstration of small trick also secretly shows a method to detect vitamin C. According to the foods containing vitamin C named by students, the teacher will smoothly proceed to the second stage of this activity—to explore whether the fruit juices contain vitamin C. 

      The fun magic trick and the short story can stimulate students' curiosity, arouse students' enthusiasm for participation, strengthen their desire to explore, promote their thinking, and reinforce their impression of the knowledge. 

Stage 2: Inquiry  

1. Learn to prepare starch-iodine solution. Through a series of small experiments to mix vegetable and fruit juices with the starch-iodine solution, students will intuitively and clearly understand the presence of vitamin C in vegetable juice. 

2. The pre-class magic trick will help students gain the initial knowledge and prepare the ground for students to successfully design related experiments. Next, the teacher will distribute worksheets to present a complete experiment procedure and to guide the students to design the specific steps of the experiment by themselves—one of the objectives of the scientific inquiry for students in the upper grades of elementary school. By filling out the worksheet, students will also cultivate a scientific attitude toward experiments. When the experimental results are different from those of other groups, students can discuss with each other in order to improve their ability to analyze problems. 

Suggested duration: 30 minutes

Teacher

Students

  1. The teacher will explain the scientific principle behind the pre-class magic trick and ask students to learn how to prepare the starch-iodine solution. 
  2. The teacher will guide students to learn that vitamin C is contained in fruits and vegetables and is important to the human body, and ask students to design their own experiments to verify the existence of vitamin C in fruits and vegetables. 

According to the teacher's demonstration, students will learn to prepare the starch-iodine solution, and verify the existence of vitamin C in fruits and vegetables through experiments designed under the guidance of the teacher. 

Activity Design: 

       Students seldom have the opportunity to conduct hands-on experiments in the school. The materials used in this experiment are some commonly seen fruits and vegetables, as well as starch and iodine tincture, which are all things familiar to them. Through the experiment, students can intuitively learn the existence of vitamin C in fruits and vegetables, and realize the importance of vitamin C to the human body through the short historical story, thereby attending to the intake of fruits and vegetables in their diet. 

      Students mainly obtain knowledge indirectly through textbooks and dictation by elders. By splitting into groups and undertaking inquiry on their own to draw experimental conclusions, students can improve their hands-on skills and cultivate the teamwork spirit. 

      Guiding students to design the specific steps of the experiment by themselves is also one of the objectives of the scientific inquiry for students in the upper grades of elementary school. The pre-class knowledge taught by the teacher will prepare the ground for students to successfully design related experiments. The teacher will subsequently distribute worksheets to help students improve the experiment design. By filling out the worksheet, students will also cultivate a scientific attitude toward experiments. When the experimental results are different from those of other groups, students can discuss with each other in order to improve their ability to analyze problems.   

Stage 3: Explanation—Through the "Starch-Iodine Solution Color Fading Experiment" and the "Experiment of Fading Starch-Iodine Solution with Vegetables and Fruits", students will discuss the scientific principle behind the experimental phenomena.   

Suggested duration: 15 minutes  

Teacher

Students

  1. Share experimental results with the whole class. 

Experiment 1: 

       (1)Measure 50ml of water with a measuring cylinder and pour it into a conical flask, and the clear water will become a white turbid solution. This is because small water-insoluble starch particles are dispersed in water. 

      (2)Add 6 drops of iodine tincture to the starch solution, and the solution will turn blue. This is because the starch will turn blue when mixed with iodine. 

       Scientific principle behind the fun magic trick

       Vitamin C can react with the iodine in the blue solution, so the starch-iodine compound in the solution will be destructed and the blue color will fade. 

Experiment 2: 

       All fruits and vegetables given can fade the blue color of starch-iodine solution, so students can conclude that these fruits and vegetables all contain vitamin C. 

       The fading speed can indicate the concentration of vitamin C in the vegetable and fruit juices. 

  1. Discussion

       Green pepper is rich in vitamin C, so Xiaoming only eats green peppers. Is this the right way? 

      Conclusion: The diet should be diverse, because there are diverse nutrients. The choice of foods should be aligned to individual needs (due to individual differences, some people may suffer allergy or diarrhea after eating certain foods). 

Since experimental classes are relatively limited in the school, the teacher will hand out the worksheets, under the guidance of which students will be able to complete the experiments step by step, fill in their experimental observations, and think carefully. 

Students will come to the following conclusion: According to individual differences, the diet should highlight diversity and the combination of different foods. 

 

Activity Design: 

      Students will conduct experiments in groups to cultivate teamwork spirit, improve practical skills, learn the simple analysis of phenomena, and cultivate the rigorous scientific spirit. Finally, the students will discuss the wrong dietary patterns to enhance the practicality of this activity. The teacher will explain the scientific principle behind the experimental phenomena and base the summary on the students' existing knowledge and experiences. 

Stage 4: Knowledge transfer. Vitamins will almost disappear after the food is cooked for a long time, so the cooking time should be as short as possible. The teacher will use the original fruit/vegetable juice and the cooked fruit/vegetable juice to conduct the comparative experiment of fading the starch-iodine solution, thereby summing up the relationship between the heating time and the vitamin C concentration in the fruit/vegetable juice. 

    Through the previous two experiments, students have learned the method of detecting vitamin C, and will continue to design new experiments independently under the guidance of the teacher in order to find out whether vegetables should be eaten raw or cooked. After summing up students' ideas, the teacher will hand out worksheets to present a complete experiment procedure and to guide the students to design the specific steps of the experiment and a comprehensive inquiry plan by themselves—one of the objectives of the scientific inquiry for students in the upper grades of elementary school, and also the necessary moves to cultivate students' scientific attitude toward experiments. 

Suggested duration: 25 minutes

Teacher

Students

  1. Generally, vegetables are eaten only after they are cooked, while fruits are eaten directly. So, will vegetables be more nutritious after being cooked? 

     To understand whether vegetables should be eaten raw or cooked, students can design experiments to get the answer. The teacher can ask students to design experiments and draw their own conclusions. 

  1. Assign the task

      Think about it: Should vegetables be eaten raw or cooked? Students will carry out experiments in groups and fill out the worksheet carefully based on their experimental observations. (see the attached photos)

 

   Upon thorough discussion in groups, students will conduct experiments and fill out the worksheet based on the experimental results, thereby cultivating their scientific attitude toward experiments. When the experimental results are different from those of other groups, students can discuss with each other in order to improve their ability to analyze problems. 

     Although Grade 3 students must have used the alcohol burner before, it's still necessary for the teacher to remind students of their safety in using the alcohol burner. 

 

Activity Design: 

    Vitamins are essential nutrients for the human body. In spite of different dietary habits, vitamins will almost disappear after the vegetable juice is cooked for a long time. Through experiments, students can fully realize that vegetables must not be cooked for a long time. Food processing methods vary from people to people, and everyone can always find the best way they like to cook their foods. 

      The teacher must actively guide students to design the specific steps of the experiment and the inquiry plan by themselves. 

      In the final session of drawing conclusions, the teacher can guide the students to put forward their own views, analyze dialectically and think from different aspects. 

Stage 5: Knowledge summing-up. Students will know the classification of vitamins and the facts that the human body can only partially synthesize vitamins and that most vitamins must be obtained from foods. The teacher will also introduce several vitamins that students are familiar with. 

      Students can try to analyze and account for the doubts they may have based on the knowledge gained from the experiments. When drawing conclusions, the teacher must guide the students to put forward their own views, analyze dialectically and think from different aspects. 

Suggested duration: 10 minutes  

Teacher

Students

  1. Question

       Based on your own life experience, please conclude whether the vegetables should be eaten raw or cooked. Please give your reasons. 

      Under the guidance of the teacher, the students will analyze from multiple perspectives, such as nutrition, taste and individual differences. 

  1. Summary

      Vitamins can be divided into fat-soluble and water-soluble vitamins (for example, the sunscreen). 

      Fat-soluble vitamins can be dissolved and stored in fat, such as vitamin A (also known as anti-dry eye vitamin), vitamin D (synthesized by skin cells in the sun), vitamin E, etc. 

      Water-soluble vitamins are soluble in water, but cannot be stored in the body. They need to be taken from foods every day. Vitamin C and vitamin B are both water-soluble vitamins. 

       Whether vegetables should be eaten raw or cooked varies from person to person. For most people, the vegetables served on the dinner table should be cooked lightly, supplemented with some refreshing vegetable salads and finally with meat cooked with less oil. 

Although the senior-grade pupils must have gained certain life experience, their knowledge of vitamins is still very limited. Through the examples named by the teacher, students will understand the importance of vitamins and learn how to eat healthily. 

 

Activity Design: 

      According to the answers given by the students, the teacher will guide the students to think from multiple aspects and start with things they are familiar with, so as to evaluate how much the students have learned and to consolidate the knowledge they have gained. Students in the upper grades of elementary school must have certain generalization, explanation and analysis abilities. By asking questions, the teacher can test their mastery of relevant knowledge points, and guide them to analyze questions dialectically before drawing conclusions. 

Worksheet
Worksheet

Worksheet for "Vitamin C in Vegetables"

Student Name:                              

Purpose of Experiment: 

1. Know some unfamiliar experimental materials and equipment: starch, iodine tincture, dropper, stirring rod, and measuring cup; 

2. Learn to prepare the starch-iodine solution; 

3. Detect vitamin C in the fruit juice. 

 

Principle of Experiment: 

1. Starch solution will change color when mixed with iodine. 

2. Vitamin C can react with the starch-iodine solution to fade its blue color. 

 

Experimental Materials and Equipment: 

Materials: starch, iodine tincture, tomato, cucumber, orange, pear, and grape; 

Equipment: dropper, mortar, conical flask, measuring cylinder, gauze, and juicer;

 

Experimental Steps: 

 

Description

Signature of Teacher

 

Level 1: Preparation of the starch-iodine solution

 

Know how to use the experimental equipment

Measure 50ml of water

Know how to use a dropper

(  ) Measure out 50 ml of water correctly

(  ) capable of using a dropper

1. Measure 50ml of water with a measuring cylinder and pour it into a conical flask; add 0.5g of starch and stir evenly.

Experimental observation (color change):   

                                                                            

                                                                           

 2. Further add 6 drops of iodine tincture to the starch solution. 

Experimental observation (color change):            

                                                                            

(  ) 1. All steps were correct and the phenomenon was obvious; 

(  ) 2. All steps were correct and the phenomenon was obvious; 

Level 2: Experiment of adding vitamin C into the starch-iodine solution

  1. Add half a vitamin C tablet into the starch-iodine solution; 
  2. Prepare another portion of starch-iodine solution, get 10ml vegetable juice or fruit juice from the teacher, and mix the two (Note: After getting five types of vegetable juice or vegetable juice from the teacher (10ml each), all group members must work together to pour the juices into the starch-iodine solution at the same time as far as possible, and observe how the color changes.)  

 

(  ) 1. All steps were correct and the phenomenon was obvious; 

(  ) 2. All steps were correct and the phenomenon was obvious; 

 

Experimental observation: 

1. Tick the fruit/vegetable juices that can fade the blue color of the starch-iodine solution. 

 

Tomato

Cucumber

Grape

Pear

Orange

Starch-iodine solution faded its blue color

 

 

 

 

 

 

2. Based on your observations, try to single out the champion and runner-up vegetables/fruits that quickly faded the blue starch-iodine solution: 

                                                                                                                                                             .

 

Experiment: Should vegetables be eaten raw or cooked? 

Purpose of Experiment: 

1. Students work in groups to mix raw vegetable juices and those cooked for different durations with the starch-iodine solution to compare the speed of color change. 

2. Students can draw conclusion on whether the vegetables should be eaten raw or cooked by generalizing and analyzing the experimental results. 

3. Students will cultivate a rigorous attitude toward experiment and be able to draw conclusion through analysis and inquiry. 

Principle of Experiment: 

Vitamin C can react with the starch-iodine solution to fade its blue color. 

Experimental Materials and Equipment: 

Materials: starch, iodine tincture, and green pepper juice (to be provided by the teacher);

Equipment: dropper, alcohol burner, asbestos net, conical flask, measuring cylinder, stopwatch, and juicer;

Experimental Steps: 

1. Prepare the starch-iodine solution and divide it into 4 equal portions; 

Experimental observation: 

 After adding 0.5 g of starch into 50 ml of water, the liquid turned into ______ color. After adding 6 drops of iodine tincture, the starch solution turned into ______ color. 

2. Experiment of mixing raw and cooked green pepper juices with starch-iodine solution. 

Heat 3 portions of 10ml green pepper juice for different durations and then leave them to cool down. After that, mix the liquids with starch-iodine solution to observe how the color changes. 

Samples to be tested

How will the blue starch-iodine solution change color after added with the following samples

Unheated green pepper juice

 

Green pepper juice heated for half a minute

 

Green pepper juice heated for two minutes

 

Green pepper juice heated for five minutes

 

Experimental conclusion (Based on your observations, please conclude whether the vegetables should be eaten raw or cooked. Please give your reasons)

                                                                                                                                                                                                                                                                                                                                                                      ?                                                                                                                                                                                   ?                                                                                                                                                                                                                                                                             

                                                                               

                                                                               

                                                                               

 

Worksheet for "Vitamin C in Vegetables"

Student Name:                              

Purpose of Experiment: 

1. Know some unfamiliar experimental materials and equipment: starch, iodine tincture, dropper, stirring rod, and measuring cup; 

2. Learn to prepare the starch-iodine solution; 

3. Detect vitamin C in the fruit juice. 

 

Principle of Experiment: 

1. Starch solution will change color when mixed with iodine. 

2. Vitamin C can react with the starch-iodine solution to fade its blue color. 

 

Experimental Materials and Equipment: 

Materials: starch, iodine tincture, tomato, cucumber, orange, pear, and grape; 

Equipment: dropper, mortar, conical flask, measuring cylinder, gauze, and juicer;

 

Experimental Steps: 

 

Description

Signature of Teacher

 

Level 1: Preparation of the starch-iodine solution

 

Know how to use the experimental equipment

Measure 50ml of water

Know how to use a dropper

(  ) Measure out 50 ml of water correctly

(  ) capable of using a dropper

1. Measure 50ml of water with a measuring cylinder and pour it into a conical flask; add 0.5g of starch and stir evenly.

Experimental observation (color change):   

                                                                            

                                                                           

 2. Further add 6 drops of iodine tincture to the starch solution. 

Experimental observation (color change):            

                                                                            

(  ) 1. All steps were correct and the phenomenon was obvious; 

(  ) 2. All steps were correct and the phenomenon was obvious; 

Level 2: Experiment of adding vitamin C into the starch-iodine solution

  1. Add half a vitamin C tablet into the starch-iodine solution; 
  2. Prepare another portion of starch-iodine solution, get 10ml vegetable juice or fruit juice from the teacher, and mix the two (Note: After getting five types of vegetable juice or vegetable juice from the teacher (10ml each), all group members must work together to pour the juices into the starch-iodine solution at the same time as far as possible, and observe how the color changes.)  

 

(  ) 1. All steps were correct and the phenomenon was obvious; 

(  ) 2. All steps were correct and the phenomenon was obvious; 

 

Experimental observation: 

1. Tick the fruit/vegetable juices that can fade the blue color of the starch-iodine solution. 

 

Tomato

Cucumber

Grape

Pear

Orange

Starch-iodine solution faded its blue color

 

 

 

 

 

 

2. Based on your observations, try to single out the champion and runner-up vegetables/fruits that quickly faded the blue starch-iodine solution: 

                                                                                                                                                             .

 

Experiment: Should vegetables be eaten raw or cooked? 

Purpose of Experiment: 

1. Students work in groups to mix raw vegetable juices and those cooked for different durations with the starch-iodine solution to compare the speed of color change. 

2. Students can draw conclusion on whether the vegetables should be eaten raw or cooked by generalizing and analyzing the experimental results. 

3. Students will cultivate a rigorous attitude toward experiment and be able to draw conclusion through analysis and inquiry. 

Principle of Experiment: 

Vitamin C can react with the starch-iodine solution to fade its blue color. 

Experimental Materials and Equipment: 

Materials: starch, iodine tincture, and green pepper juice (to be provided by the teacher);

Equipment: dropper, alcohol burner, asbestos net, conical flask, measuring cylinder, stopwatch, and juicer;

Experimental Steps: 

1. Prepare the starch-iodine solution and divide it into 4 equal portions; 

Experimental observation: 

 After adding 0.5 g of starch into 50 ml of water, the liquid turned into ______ color. After adding 6 drops of iodine tincture, the starch solution turned into ______ color. 

2. Experiment of mixing raw and cooked green pepper juices with starch-iodine solution. 

Heat 3 portions of 10ml green pepper juice for different durations and then leave them to cool down. After that, mix the liquids with starch-iodine solution to observe how the color changes. 

Samples to be tested

How will the blue starch-iodine solution change color after added with the following samples

Unheated green pepper juice

 

Green pepper juice heated for half a minute

 

Green pepper juice heated for two minutes

 

Green pepper juice heated for five minutes

 

Experimental conclusion (Based on your observations, please conclude whether the vegetables should be eaten raw or cooked. Please give your reasons)

                                                                                                                                                                                                                                                                                                                                                                      ?                                                                                                                                                                                   ?                                                                                                                                                                                                                                                                             

                                                                               

                                                                               

                                                                               

 

Assessment
Assessment

      According to the students' experimental competence and on-site performance, the teacher can provide necessary guidance, feedback and correction advice in a timely manner, and give comments on the experimental sheet. In addition, the teacher can also evaluate the effectiveness of this activity based on the worksheets submitted by students. 

      According to the students' experimental competence and on-site performance, the teacher can provide necessary guidance, feedback and correction advice in a timely manner, and give comments on the experimental sheet. In addition, the teacher can also evaluate the effectiveness of this activity based on the worksheets submitted by students.