Yasser Saad-Photosynthesis-Phenol Red Setup

Summary

In this transcript, the instructor demonstrates an experiment related to photosynthesis using phenol red and carbon dioxide. The technique involves adding phenol red to a solution and bubbling CO2 through it to observe how the pH changes. As the CO2 is absorbed by the plant during photosynthesis, the solution's pH increases and the color shifts back to red. The instructor sets up a control experiment and explains the safety precautions, including the use of paper towels to prevent spills. The overall objective is to show how plants absorb CO2, affecting the pH of their environment.

Takeaways

• 😀 Phenol red is used as a pH indicator to demonstrate the effects of CO2 on the pH of a solution.
• 😀 When CO2 is bubbled through the solution, it lowers the pH, causing the phenol red to turn yellow.
• 😀 The plant will absorb the CO2 for photosynthesis, which will cause the pH to rise and the solution to turn back to red.
• 😀 The experiment is designed to show how plants use CO2 during photosynthesis and affect the surrounding environment.
• 😀 The use of a control setup, where no plant is present, allows for comparison to see the effect of the plant on CO2 levels.
• 😀 The paper towel is used as a safety measure to avoid spilling the solution or creating a mess during the experiment.
• 😀 The experiment setup includes a heat sink (a beaker full of water) to prevent the plant from overheating during the light exposure.
• 😀 The instructor emphasizes safety precautions, such as students not drinking from the straws used in the experiment.
• 😀 The color change in the solution will indicate whether photosynthesis is occurring, with red indicating a return to normal pH levels.
• 😀 The instructor adds CO2 to initiate the experiment and makes predictions about the results based on plant behavior.

Q & A

What is the purpose of using phenol red in this experiment?

Phenol red is used as a pH indicator. It changes color depending on the pH of the solution, turning yellow in acidic conditions and red in neutral or slightly basic conditions. This allows the experiment to visually track changes in pH caused by CO2 absorption during photosynthesis.

What effect does CO2 have on the pH of the solution in the experiment?

When CO2 is bubbled into the solution, it forms carbonic acid, which lowers the pH, turning the phenol red solution from red to yellow. This acidic condition is temporary and will reverse as the plant performs photosynthesis.

How does the experiment simulate the role of CO2 in photosynthesis?

CO2 is introduced into the solution by bubbling air from human exhalation through a straw. The plant uses this CO2 for photosynthesis, and the experiment monitors the resulting pH changes as the CO2 is consumed.

What is the role of the plant in this experiment?

The plant's role is to absorb CO2 from the solution during photosynthesis. As the plant consumes CO2, the pH of the solution rises, causing the phenol red to revert from yellow back to red, indicating that photosynthesis is occurring.

Why is there a control setup in the experiment?

The control setup, which contains the phenol red solution but no plant, helps establish a baseline for comparison. It shows what happens to the pH when no photosynthesis occurs and CO2 is not being consumed.

What does the color change from yellow back to red indicate?

The color change from yellow back to red indicates that the plant has consumed CO2 during photosynthesis, which has caused the pH of the solution to increase, returning it to a neutral or slightly basic state.

Why does the professor use a paper towel during the CO2 introduction?

The professor uses a paper towel to absorb any splashes of the phenol red solution during the CO2 introduction process. This is a safety precaution to avoid spilling the solution on the lab environment or themselves.

What might happen if students were to blow into the solution without proper precautions?

If students were to blow into the solution without precautions, they might inadvertently cause a mess or spill the solution, as CO2 bubbles could spill over. The professor uses a paper towel to prevent this and ensures safety.

What is the significance of the beaker filled with water placed in the experiment?

The beaker of water serves as a heat sink to absorb any excess heat, preventing the plant from getting too warm. The plant needs light for photosynthesis, not excess heat, which is why the heat sink is used.

How does the setup reflect the process of photosynthesis?

The setup reflects photosynthesis by providing the plant with CO2, water, and light. The plant absorbs CO2 for photosynthesis, and the experiment measures how this affects the pH of the solution, demonstrating the consumption of CO2 and the subsequent production of oxygen and glucose.