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Diffusion
Task with Student Directions

Grades 9-12 Performance Task
Contributed by: New York State Education Department (NYSED)
Developed through University of Buffalo and NORC (1991)

Part A - Experiment Design

Introduction:

This laboratory test presents a problem. Your task in Part A is to plan and design an experiment to solve the problem. You will have 30 minutes to complete Part A. At the end of the 30 minutes, your answer sheet will be collected. You will then receive separate directions for Part B. In Part B you will use materials and equipment provided in the laboratory kit to collect experimental data for this problem. You may wish to do your preliminary planning on the sheet labelled "Working Copy." Write this plan on the appropriate answer sheet in your test booklet.

Problem:

Diffusion is a process by which substances enter and leave cells. Your problem is to design an experiment to test the effects of two variables (time and concentration) on diffusion of potassium permanganate into potato cubes.

 

a) State a HYPOTHESIS for this investigation that can be used to test the effects of time and concentration on diffusion.

b) Under the heading PROCEDURE list in order the steps you will use to solve the problem. You may include a diagram to help illustrate your plans for the experiment. Include any safety procedures you would follow.

c) Construct a DATA TABLE or indicate any other method that you could use to record the observations and results that will be obtained.

PLEASE NOTE: In Part A you are NOT to proceed with any part of the actual experiment. You are just to plan and organize a way to investigate the problem.

Materials:

  • 2 firm potatoes
  • Metric ruler (30 cm)
  • 3 small beakers (approx. 150 ml)
  • 1%, 5%, and 10% solutions of potassium permanganate (in beakers)
  • Forceps
  • Scalpel
  • Stopwatch/clock
  • Paper towels
  • Experiment Display Sheet
  • Waste container
  • Graph paper

 

WORKING COPY

PART A - Experiment Design

This sheet is provided as a work space (or scrap sheet).
Be sure to enter your final plan on the appropriate answer sheets.
No work on this sheet will be considered for credit.

 

 

 

ANSWER SHEET

PART A - Experiment Design

Organize your experiment design under the following headings:
HYPOTHESIS, PROCEDURE, and DATA TABLE.
Use the front and back of these sheets if necessary.

HYPOTHESIS




PROCEDURE (Include diagram if appropriate)

 

 

 

DATA TABLE (For results and observations)

 

 

 

Part B - Experiment Report

You will have 50 minutes to complete this part. Record your work for Part B on the answer sheet under the appropriate headings. Perform the experiment by following the steps outlined in the procedure (listed below). Under the heading RESULTS record your observations and measurements for the experiment. Use written statements, descriptive paragraphs, tables of data, and/or graphs where appropriate. Construct a GRAPH which presents the relationship between the distance of diffusion into the potatoes and time and concentration. Under the heading CONCLUSIONS write an interpretation of your results. State the effect that time and concentration have on diffusion.

At the end of 50 minutes, your answer sheet for Part B will be collected.

Safety

CAUTION: SLICE AWAY FROM FINGERS TO AVOID CUTS.
HANDLE POTATO CUBES WITH FORCEPS ONLY.

 

Procedure:

  1. Using a scalpel, cut 12 cubes from a potato. Each side of the cubes should measure approximately 1 cm. Be sure that there is no skin on anyof the cubes.

    CAUTION: SLICE AWAY FROM FINGERS TO AVOID CUTS.
    HANDLE POTATO CUBES WITH FORCEPS ONLY.






  2. Place 4 potato cubes in each of the three beakers of different concentrations of potassium permanganate. Note the exact time the cubes were added to the solutions.

  3. With forceps, remove one cube from each solution every 5 minutes and place on a paper tower. Slice each cube in half with a scalpel. CAREFULLY dry the scalpel before slicing each cube.

  4. Remove the Experiment Display Sheet from the back of the test booklet. Measure and record the distance that the solution has diffused into each potato for each time interval. After measuring, place the cubes on the Experiment Display Sheet for later checking of results or verifying conclusions.

  5. Record the RESULTS of your experiment in the data table. Enter the distances for each concentration and time.

  6. Construct a GRAPH for these results.

  7. Based on your data table and graphing of the results, state your CONCLUSIONS as to how the length of time in solution and the concentration of the solution influence the distance of he diffusion.

    When you are finished with all work, discard the potato cubes in a container labelled "WASTE."

 

ANSWER SHEET

PART B - Experiment Report

Organize your experiment report under the following headings:
RESULTS, GRAPH, and CONCLUSIONS.
Use the front and back of these sheets if necessary.

RESULTS

 
Distance of diffusion
(in mm)
Distance of diffusion
(in mm)
Distance of diffusion
(in mm)
Concentration of potassium permanganate
After 5 minutes
After 10 minutes
After 20 minutes
1%
      
5%
      
10%
      

 

Construct your GRAPH on the graph paper provided.

 

CONCLUSIONS

 

 

 

 

 

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