Question

what is your prediction for this experiment?

a. as photosynthesis progresses, the level of carbon dioxide will decrease.
b. as photosynthesis progresses, the level of carbon dioxide will increase.
c. as photosynthesis progresses, the level of carbon dioxide will remain unchanged.

what is your strategy?

a. i will place a plant in an environment with carbon dioxide and light for photosynthesis to occur. i will use a ph indicator to monitor the level of carbon dioxide. i will compare the results to a negative control without a ph indicator.
b. i will place a plant in an environment with carbon dioxide and light for photosynthesis to occur. i will use a ph indicator to monitor the level of carbon dioxide. i will compare the results to a negative control without a plant.
c. i will place a plant in an environment without carbon dioxide and in the light for photosynthesis to occur. i will use a ph indicator to monitor the levels of carbon dioxide. i will compare the results to a negative control without a plant.

Explanation:

Analyze the prediction question

Using the Photosynthesis Chemical Equation and Photosynthesis Reactants knowledge points

During photosynthesis, autotrophic organisms like plants utilize light energy to convert carbon dioxide (\(\text{CO}_2\)) and water (\(\text{H}_2\text{O}\)) into glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) and oxygen (\(\text{O}_2\)):

$$ 6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow{\text{light}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 $$

Because carbon dioxide is consumed as a reactant, its concentration in the closed experimental environment will decrease over time as photosynthesis progresses.

Analyze the strategy question

Using the Experimental Controls knowledge point

To test this prediction, we must design a controlled experiment:

1. Experimental Setup: Place a plant in a sealed environment containing both light and carbon dioxide so that photosynthesis can actively occur.
2. Measurement: Use a pH indicator (such as phenol red or bromothymol blue) to monitor carbon dioxide levels, as dissolved \(\text{CO}_2\) forms carbonic acid and changes the pH of the solution.
3. Control Setup: To prove that the change in carbon dioxide is specifically due to the plant's biological activity (photosynthesis) and not spontaneous environmental changes, a negative control is required. A proper negative control must lack the active biological agent (the plant) but contain all other components (the environment, light, and the pH indicator).

Answer:

Question 1

• A. As photosynthesis progresses, the level of carbon dioxide will decrease. (Correct answer)
• B. As photosynthesis progresses, the level of carbon dioxide will increase.
• C. As photosynthesis progresses, the level of carbon dioxide will remain unchanged.

Question 2

• A. I will place a plant in an environment with carbon dioxide and light for photosynthesis to occur. I will use a pH indicator to monitor the level of carbon dioxide. I will compare the results to a negative control without a pH indicator.
• B. I will place a plant in an environment with carbon dioxide and light for photosynthesis to occur. I will use a pH indicator to monitor the level of carbon dioxide. I will compare the results to a negative control without a plant. (Correct answer)
• C. I will place a plant in an environment without carbon dioxide and in the light for photosynthesis to occur. I will use a pH indicator to monitor the levels of carbon dioxide. I will compare the results to a negative control without a plant.