CHEMISTRY NOW: Ethylene Gas Investigation (Grades 9-12)

Objective:


Students will design and 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. Students will discuss the role of ethylene gas in this process.


Introduction Notes:


CHEMISTRY NOW: Ethylene Gas Investigation

 

 

Subject Area: Chemistry                                                        

Grade Level:  High School Chemistry                                   

Lesson Title:  Ethylene Gas Investigation       

National Science Education Standards:                                                                                        

  •   Science as Inquiry: 9-12

  • 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; basic organic chemistry (alkenes)

 

Purpose: To give students an understanding of how tomatoes ripen and what conditions allow them to ripen the 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 new substance or substances

 

ethylene gas- an organic compound, C2H4 (IUPAC name = ethene), the simplest alkene, which is a plant hormone

 

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 design and conduct an experiment that allows them to observe the ripening of tomatoes under different conditions.

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

3. Students will discuss the role of ethylene gas in this process.

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

-          safety goggles (required)

-          several green tomatoes on the vine

-          small flowering plants or seeds

-          paper bags (shopping bag size)

-          cardboard box

-          newspaper

-          twine

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

-          jars

-          plastic containers made for ripening fruit or to keep fruit from ripening (available from department stores, Tupperware, etc.)

-          refrigerator (optional)

Procedure: ­    

1. Introduce the topic of ripening by displaying unripe and ripe fruit such as bananas, avocados, apples and tomatoes. Discuss the role of ethylene gas in this process. You might also want to introduce the theory that ethylene gas also plays a role in germination of seeds and blossoming of flowers and other similar changes in plants. Discuss with students how we can design an experiment that allows us to investigate the effect ethylene gas production has on a plant system. Focus students on the idea that ethylene gas produced by the fruit is key to the process, and that this gas diffuses out of ripening fruit and other plants. As a gas in the air, it can influence other plants and plant processes nearby. 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 investigate the effect of ethylene gas production on a ripening fruit, plant, flowers or seeds?

         What is diffusion? How might a gas diffuse from one piece of fruit to another?

         What other plants might respond to the production of ethylene gas? How?

         How large (or small) a distance prevents (or allows) the ethylene gas to be effective?

 

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 protocols should be followed incorporating safety equipment.

4. Students may also wish to design investigations involving other plants, either in place of the tomato ripening investigation or as a follow up or extension. Some possible topics include:

a. Some flowering plants are also affected by ethylene gas production. What happens to flowers (or flowering plants) exposed to a source of ethylene gas?

b. Ethylene gas may also encourage seed germination. Does the presence of a source of ethylene gas speed the germination of seeds?

 

5. Work with students to develop a procedure that allows them to investigate the effect of ethylene gas production on ripening of fruit or to try ideas of their own. Guide them to develop a procedure that is technically correct and allows them time to observe the effect of the ethylene gas production. Encourage students to develop an experiment with a control 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. Discussion of some commonly recommended “old wives’ tales” about ripening fruit might help students who are struggling to come up with a plan. These students may wish to focus on a more basic investigation (Basic Procedure for Tomato Ripening Investigation) while some students can challenge themselves to investigate other effects of ethylene gas. There are some theories that fruit ripens better sitting on its stem side as opposed to stem side up. There are also theories that unripe bananas will produce enough ethylene gas to aid the ripening process in tomatoes. Other “old wives’tales”are that fruit will ripen better in these conditions:

    1. a. storing the fruit in a paper bag with the bag top rolled down
    2. b. storing on a sunny window sill
    3. c. storing in cardboard box wrapped in newspaper
    4. d. storing them still attached to the vines, hanging in a dark spot
    5. e. storing in a dark cabinet
    6. f. storing the unripe tomatoes with other unripe fruit such as bananas

7.  Basic Procedure for Tomato Ripening Investigation:

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

                                                              - paper shopping bag

                                                             - cardboard box

                                                            - some newspaper

                                                            - plastic bags (including, if available, commercially-available bags advertised as helping to ripen fruit)

                                                             - twine to hang vines

  1. c. 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. d. Some students may also want to investigate this process by trying to prevent it. Strategies such as wrapping a tomato in foil or a plastic sandwich bags will also yield interesting and educational results.
  1. e. 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.

8. Basic procedure for an investigation of ethylene gas’s effect on a flowering plant:

    1. a. Obtain several pieces of unripe fruit (banana or tomato) of the same size and ripeness to use as sources of ethylene gas.
    2. b. Obtain a number of identical small flowering plants (small potted mini rose bushes for example).
    3. c. Set up the following:

                                                              i.      In one area, place the flowering plant close to the unripe piece of fruit.

                                                            ii.      In a second area, place the flowering plant at a short distance (1 m or so) from the piece of fruit.

                                                          iii.      In a third area, place the flowering plant at a greater distance (2 m or so) from the piece of fruit.

                                                          iv.      Other options include placing the ripening fruit and/or plant in a paper or plastic bag to try to prevent diffusion of the ethylene gas.

                                                            v.      Make certain that set-ups each get the same amount of water and sunlight so that there are no other variables in play.

    1. d. Make hypotheses about what will happen in each set-up.
    2. e. Observe the set-ups for several days and record observations.
    3. f. Allow sufficient time to observe blossoming of flowers

 

9. Students should clearly communicate their plans, highlighting the variables being tested and their hypotheses. Students may need to do some research on their topics to properly focus their investigation.

10. Have students draw a conclusion about which methods worked best and which were least effective. Their discussion should include explanation of how diffusion of ethylene gas is involved.

11. Students may present their findings to the class using posters, slideshows (PowerPoint works wellt) or videos they found in their research. They can incorporate any pictures or videos they took as well.

12. After the students have drawn conclusions about their investigations, lead a discussion of possible reasons. Explain that ethylene gas is involved in the ripening process; closing the container keeps the ethylene near the fruit. Ethylene gas diffuses out of ripening fruit and 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

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

 

Student Worksheet for Ethylene Gas Investigation

 

 

Experiment Title: ___________________Date: __________Name: ________________

 

Student Question or Objective(s):

____________________________________________________________________

 

Materials:        

____________________________________________________________________

 

____________________________________________________________________

 

____________________________________________________________________

 

____________________________________________________________________

 

____________________________________________________________________

 

 

Procedure: (Include any safety concerns or requirements)

 

1. ____________________________________________________________________

2. ____________________________________________________________________

3. ____________________________________________________________________

4. ____________________________________________________________________

5. ____________________________________________________________________

6. ____________________________________________________________________

7. ____________________________________________________________________

8. ____________________________________________________________________

9. ____________________________________________________________________

10. ____________________________________________________________________

11. ____________________________________________________________________

 

 

Data and Observations:

 

Location/Set up

 Observations

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Analysis of Data:

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

 

Conclusion:

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

 

Close NBC Learn

FILTERING

If you are trying to view the videos from inside a school or university, your IT admin may need to enable streaming on your network. Please see the Internet Filtering section of our Technical Requirements page.

DVDs AND OTHER COPIES

Videos on this page are not available on DVD at this time due to licensing restrictions on the footage.

DOWNLOADING VIDEOS

Subscribers to NBC Learn may download videos and play them back without an internet connection. Please click here to find out more about subscribing or to sign up for a FREE trial (download not included in free trial).

Still have questions?
Click here to send us an email.

Close NBC Learn

INTERNATIONAL VISITORS

The Science of the Olympic Winter Games videos are only available to visitors inside the United States due to licensing restrictions on the Olympics footage used in the videos.

FILTERING

If you are trying to view the videos from inside a school or university, your IT admin may need to enable streaming on your network. Please see the Internet Filtering section of our Technical Requirements page.

DVDs AND OTHER COPIES

The Science of the Olympic Winter Games is not available on DVD at this time due to licensing restrictions on on Olympic footage.

DOWNLOADING VIDEOS

Subscribers to NBC Learn may download videos and play them back without an internet connection. Please click here to find out more about subscribing or to sign up for a FREE trial (download not included in free trial).

Still have questions?
Click here to send us an email.

Close NBC Learn

Choose your product

For NBC Learn in Blackboard™ please log in to your institution's Blackboard™ web site and click "Browse NBC Learn"

Close NBC Learn

If you have received a new user registration code from your institution, click your product below and use the "Register now" link to sign up for a personal account.

For further assistance, please contact our NBC Learn Support Team and we'll be happy to assist you.