Design and carry out an experiment to investigate a relationship between the surface area of a piece — Kinetics Chemistry Question
Problem Context
Design and carry out an experiment to investigate a relationship between the surface area of a piece of raw potato and the rate of decomposition of hydrogen peroxide. You may use only those materials available at your experimental station. You will be asked to describe the method you developed to carry out this investigation.
Give a brief description of your experimental plan.
Before beginning your experiment, you must get approval (for safety reasons) from the examiner.
Model Answer
A good plan included a detailed description of a method to observe the rate of reaction. It would also include a plan for varying the surface area of the potato. Finally, the plan needed to account for the importance of controlling the volume of peroxide.
For example, a good plan might consist of these steps.
1) Cut the potato into different size cubes, such as 2 cubes of 0.5 cm on a side and 2 cubes of 1.0 cm on a side.
2) Measure 2.0 mL of H2O2 into a test tube or graduated cylinder and add 3 drops of detergent..
3) Shake to generate a small amount of foam for a starting point. Measure the height of the foam column or read the volume of the foam directly if using a graduated cylinder.
4) Drop in one cube of potato and start a timer.
5) At appropriate intervals, measure the height of the foam column or read the volume of the foam directly if using a graduated cylinder.
6) Repeat steps 2-5 for other potato pieces.
An average plan was either missing one of these three components or had less detail in two or more of these components.
A weak plan had minimal detail about how the experiment would be conducted.
Record your data and other observations.
Model Answer
A good experimental section included these points.
1) Appropriate measurements of
a. reaction rate or progress.
b. dimensions of the potato pieces used.
c. time.
d. volume of H2O2 used.
2) Multiple (at least two) trials for each different surface area of the potato piece.
3) Appropriate quantitative detail such as
a. precision in the trials.
b. averaging trial data.
c. description of any calculation methods used, such as for determining the surface area of the potato piece.
An average experimental section was either missing one of these three components or had less detail in two or more of these components.
A weak experimental section had minimal detail about how the experiment was conducted and what observations were made.
What relationship did you have find between the surface area of a raw potato and the rate of decomposition of hydrogen peroxide? Support your conclusion with your experimental evidence.
Model Answer
A good discussion included these points.
1) Calculations or graphical determinations of the relationship between surface area and rate of decomposition of hydrogen peroxide.
2) An appropriate description of the scientific reasoning utilized.
3) An accurate conclusion supported by the experimental observations and data reported.
Note: Points were not deducted for correct and reasoned discussion of an experiment with seemingly anomolous results.