Carbon Dioxide and Bromothymol Blue

The video tutorial demonstrates an experiment to observe gas exchange in plants through photosynthesis. Using bromothymol blue (BTB) as an indicator, the experiment tracks color changes in a solution as carbon dioxide is added and then absorbed by Elodea, a plant. The setup includes control test tubes and a heat lamp to facilitate photosynthesis. After 24 hours, the color changes indicate the absorption of CO2 by the plant, demonstrating the process of photosynthesis.

What is the main purpose of using bromothymol blue (BTB) in this experiment?

• To change the pH of the solution

• To indicate the presence of carbon dioxide

• To provide nutrients to the plants

• To measure the temperature of the solution

What color does BTB turn when there is little or no carbon dioxide present?

• Red

• Green

• Yellow

• Blue

How much bromothymol blue (BTB) is added to the 30 milliliters of water in the beaker?

• 5 milliliters

• 10 milliliters

• 1 milliliter

• 2 milliliters

What is the purpose of creating a control test tube in this experiment?

• To compare the results with a standard

• To add more carbon dioxide

• To measure the temperature

• To provide light to the solution

What gas is being exchanged when blowing into the beaker with a straw?

• Hydrogen

• Nitrogen

• Carbon dioxide

• Oxygen

What is the color of the solution after adding carbon dioxide by blowing into it?

• Red

• Purple

• Greenish yellow

• Blue

Why is elodea used in this experiment?

• It is easy to grow and readily available

• It does not require light for photosynthesis

• It changes color in the presence of carbon dioxide

• It is a rare plant

What is the purpose of placing the test tubes in front of a heat lamp for 24 hours?

• To increase the temperature of the solution

• To provide light for photosynthesis

• To evaporate the water

• To sterilize the solution

What was the color of the solution in the test tube with elodea after 24 hours?

• Red

• Greenish yellow

• Green

• Blue

What does the color change in the test tube with elodea indicate?

• Increase in temperature

• Decrease in oxygen

• Decrease in carbon dioxide

• Increase in carbon dioxide