AP LAB 1 – OSMOSIS AND DIFFUSION

WRITE-UP GUIDELINES

Title

  • AP Lab 2 – Osmosis and Diffusion

I. Abstract

II. Introduction

  • Brief overview and purpose for part A, B, and E.
  • Hypothesis for Part Aand B only.

III. Materials & Methods

  • Provide a brief summary (2-3 sentences per part) of procedure followed in Parts A, B, and E
  • Then write, “For a complete listing of materials and methods, see lab protocol titled . . . “

IV. Data

  • Part A
  • Table 1
  • Graph 1
  • Part B
  • Table 2
  • Part E
  • 2 Onion Drawings – Before and After

Remember all graphs, data tables, and drawings must be hand-constructed using pencil/pen & ruler. Include a title for each. Graph axes must be labeled and axes spacing must be correct/appropriate.

V. Questions (Answer in complete sentences that re-state the question.)

Diffusion - Part A Questions

  1. Which substance(s) are entering the bag and which are leaving the bag? What experimental evidence supports your answer?
  2. Explain the results you obtained. Include the concentration differences and membrane pore size in your discussion.
  3. Quantitative data uses numbers to measure observed changes. How could this experiment be modified so that quantitative data could be collected to show that water diffused into the dialysis bag?
  4. What results would you expect if the experiment started with glucose and KI solution inside the bag and only starch and water of the outside? Why?

Osmosis - Part B Questions

  1. In part B, what caused the mass of the dialysis bags to change? Was there more or less water in the dialysis bags at the conclusion of the experiment? Explain.
  2. Was the distilled water in the beakers hypertonic or hypotonic in relation to the sucrose solutions found in the dialysis bags?
  3. Suppose the dialysis bags were placed in beakers containing a 0.6 M sucrose solution as opposed to distilled water. How do you think your results would change?

Onion Cell Plasmolysis - Part E Questions

  1. What is plasmolysis and why did the onion cell plasmolyze?
  2. What are the effects on cells when they are placed in a hypotonic solution, a hypertonic solution, and an isotonic solution?
  3. Why cant humans drink salt water for hydration?

VI. Conclusion

  • Re-address purpose for Part A, B, and E.
  • Re-address hypothesis for Part A.
  • If your hypothesis was correct, confirm it.
  • If your hypothesis was incorrect, explain why it was incorrect.
  • Re-address hypothesis for Part B.
  • If your hypothesis was correct, confirm it.
  • If your hypothesis was incorrect, explain why it was incorrect.
  • Possible sources of error.
  • Do not make a blanket statement such as “calculations were off, measurements were off, etc.”
  • Think of how these errors would/could affect the outcome of the experiment.