CHEMISTRY NOW: Ripening Tomatoes (Grades 5-8) Print

Objective:

Students will be able to observe the ripening of tomatoes. Students will conduct an experiment that allows them to observe the ripening of tomatoes under different conditions. Students will be able to evaluate the effectiveness of various strategies for ripening tomatoes.


Introduction Notes:

CHEMISTRY NOW: Ripening Tomatoes

 

 

Subject Area: Chemistry                                                        

Grade Level:  Middle School Chemistry                               

Lesson Title:  Ripening Tomatoes       

National Science Education Standards: 

  • Science as Inquiry: 5-8                                                           

  • Science as Inquiry: 9-12                                              

 

Physical Science Education Standards:

  • Properties and Changes of Properties: 5-8                   
  • Structure and Properties of Matter: 9-12
  • Chemical Reactions: 9-12                                            

 

Suggested Prior Knowledge:  concepts of chemical changes; chemical properties of gases, especially diffusion of gases

 

Purpose: To give students an understanding of how tomatoes ripen and what conditions allow them to ripen best. To allow students to observe a chemical change that happens in nature.

Key Vocabulary:  

 

chemical change - change in which substance or substances are changed into a new substance or substances

 

ethylene gas - gas given off by ripening fruit that aids in the ripening process

 

diffusion - movement of a substance from an area of high concentration (lots of the gas) to an area of lower concentration (less of the gas)

 

Objectives:      

1. Students will be able to observe the ripening of tomatoes.

2. Students will conduct an experiment that allows them to observe the ripening of tomatoes under different conditions.

3. Students will be able to evaluate the effectiveness of various strategies for ripening tomatoes.

Materials: (as needed depending on the design of the experiment)

- safety goggles

- several green tomatoes on the vine

- paper bags (shopping bag size)

- cardboard box

- newspaper

- twine

- plastic bags (some are even commercially available that claim to ripen fruit)

- jars

- refrigerator (optional)

Procedure:     

1. Introduce the topic of ripening by displaying unripe and ripe fruit such as bananas, apples and tomatoes. You might want to allow students to compare the taste as well as the appearance of the fruits in each state. Discuss with students how we can design an experiment that allows us to find the best way to ripen fruit, such as a tomato, off the plant without allowing it to rot. You might need to focus them on the idea that a gas produced by the fruit is key to the process. Introduce or review the concept of diffusion of gases. Begin with a leading question and follow-up:

         - What is the difference between ripe and unripe fruit?(bananas, tomatoes, apples)

         - Which tastes and looks better?

         - What kind of experiment can we do to find a good way to ripen fruit off the plant?

 

2. A brief review of gases and their properties may be helpful. Discuss movement of gas particles, and diffusion especially. Also discuss how gas particles can move in and out of plants.

 

3. Lab safety equipment should be used, and safety protocols should be followed.

 

4. Discuss some commonly recommended “old wives’ tales” about ripening fruit. (There are also some theories that fruit ripens better sitting on its stem side as opposed to stem side up.) Some of these “old wives’ tales” are that fruit ripens better in these conditions:

a. storing the fruit in a paper bag with the top of bag rolled down

b. storing on a sunny window sill

c. storing in cardboard box wrapped in newspaper

d. storing them still attached to the vines, hanging in a dark spot

e. storing in a dark cabinet.

 

5. Work with students to develop a procedure that allows them to investigate the results of some or all of these methods or to try ideas of their own. Guide them to develop a plan, similar to that in this lesson plan, that is technically correct and allows them time to observe the changes in the tomatoes. Encourage students to develop an experiment with a control of some sort (tomato on desk top possibly) and a limited number of variables (one variable/set up is best). This may be carried out with small groups of students working together or as a whole class working together.

 

6. Basic Procedure:

  1. Obtain several unripe tomatoes (or other fruit such as apples or bananas)
  2. Obtain materials:

- paper shopping bag

- cardboard box

- some newspaper

- plastic bags (including, if available, commercially-available bags advertised as promoting the ripening of fruit)

-  twine to hang vines

  1. Set up several different ripening environments to test such as:

                                                       -  Tomatoes alone in paper bag with bag top rolled shut

                                                       -  Tomatoes with ripening banana in paper bag with bag top rolled shut

                                                       - Tomatoes in plastic bag tied closed

                                                       - Tomatoes on a sunny window sill

                                                      - Tomatoes hanging on the vine in the dark

                                                          - Tomatoes hanging on the vine in the sun

  1. Allow several days for tomatoes to ripen. Observe and record the condition of the tomatoes each day. If you have access to a digital camera, this is a great way to record the changes in the fruit over time.

 

7. Have students draw a conclusion about which methods worked best and which were least effective.

 

8. Students may present their findings to the class using posters or even slideshows (PowerPoint works well.) They can incorporate any pictures they took as well.

 

9. After the students have drawn conclusions about their methods, lead a discussion of possible reasons these methods worked. Explain that ethylene gas is involved in the ripening process; closing the container keeps the ethylene near the fruit. Ethylene gas, diffusing out of already-ripening fruit, helps other fruit ripen. If the gas is trapped in the container, the increased concentration of the ethylene gas helps fruit ripen. If the fruit is not in a closed container, the ethylene gas escapes into the room as it is produced (it diffuses throughout the entire available space).

     

Additional Resources:

 http://www.flinnsci.com/resources_display.asp?catID=8

         http://www.wikihow.com/Ripen-Green-Tomatoes

         http://gardening.about.com/od/growingtips/qt/Green_Tomato.htm

         http://www.scientificamerican.com/article.cfm?id=origin-of-fruit-ripening

         http://en.wikipedia.org/wiki/Gas_exchange

         http://answers.yahoo.com/question/index?qid=20080901025517AA69ZJ2

         http://chemistry.about.com/od/gas2/a/gasproperties.htm

 

 

 

 

 

 


 

Student Worksheet for Ripening Tomatoes

 

 

Experiment Title: __________________Date: _________Name: ________________

 

Student Hypothesis: ______________________________________________________

 

Materials:        

_______________________________________________________________________

 

_______________________________________________________________________

 

_______________________________________________________________________

 

 

Procedure: 

1. ___________________________________________________________________

2. ___________________________________________________________________

3. ___________________________________________________________________

4. ___________________________________________________________________

5. ___________________________________________________________________

6. ___________________________________________________________________

7. ___________________________________________________________________

8. ___________________________________________________________________

9. ___________________________________________________________________

10. ___________________________________________________________________

11. ___________________________________________________________________

 

 

Data and Observations:

 

Location

 Observations

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Conclusion: 

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

 

 

What conditions made the tomato ripen the fastest? Why do you think this is true?

 

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

 

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