CARBON DIOXIDE PRODUCTION BY GERMINATING SEEDS



CARBON DIOXIDE PRODUCTION BY GERMINATING SEEDS- Teachers Notes

MATERIALS:

50 beans 1 test tubes or small beaker

1 one-quart jars with airtight lids Bromothymol blue solution

Beaker or small jar to soak seeds Water

Paper towels

PROCEDURE:

1. Obtain 1 jar and place several layers of moist paper towels in the bottom.

2. Half of the lab groups will place 50 pre-soaked (the night before) beans in your jar. The other half will not use beans. Mrs. Evans will tell you which group you are in.

3. Fill 1 small beaker halfway with Bromothymol blue and place it in the center of your jar. Nestle beans around jar (if you have beans).

4. Place the lids on the jars tightly and keep the jars on the windowsill.

5. Observe jars the next day and record data in the DATA TABLE. Remember, the observation after the jars are set-up, is for day zero.

|DATA TABLE: Carbon Dioxide Production by Germinating Seeds |

|Date |Jars with Beans |Jar without Beans |

|Day Zero |blue |blue |

|1 |Yellow/green |blue |

|2 |Yellow/green |blue |

HYPOTHESIS/PREDICTION: Create a hypothesis for this lab. What do you think will happen in each of the jars? Explain. When germinating seeds are placed in a sealed environment the CO2 that is released during the germination process will create a chemical reaction with the brom. Blue that is used as an indicator inside of the environment.

Questions: (Students should know that bromothymol blue reacts (changes color) depending on the pH. The jars that are neutral should be blue because water is neutral. When CO2 is added to the bromothymol blue and water solution, the pH is decreased as the CO2 is dissolved slightly, and carbonic acid is formed. This slightly acidic solution becomes yellow or green.)

1. Why do we use bromothymol blue as an indicator? Because it changes color in the presence of CO2

2. Which of the jars showed change? What change was seen? Explain what caused this change.

The jars with the germinating seeds changed because of the releasing of the CO2 which causes a color change in the bromothymol blue. Color change is explained above.

Conclusion: Did you accept or reject your hypothesis? Explain your reasons to support your answer.

Accept the hypothesis, because a color change did occur in the container that had the germinating seeds alone.

The container in the center has the bromothymol blue and the germinating beans are placed around the outside

of that container. The larger container needs to be sealed to prevent environmental contaminants.

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